— for each image or video add a caption and description.
— make all the text professional and succinct without losing key details
— make the information as organized and as aesthetically pleasing as possible
— don't just take my notes from the prompt, refine it before putting it on the page
a) in week9.html, add a new subsection to the individual assignment for dome and arrow and add these notes for drystone casting plan:
subsection: casting
subsubsection: domes
melt the wax in the cup
paint brush it on the mold
100C melt it and pour out leaving a thin layer
clamp the molds
pour
subsubsection: arrow
clamp the molds
paintbrush a slurry on the thin layers
reclamp
pour
b) i need to add these images and videos in new subsubsections in this order in individual assignment or group assignment (each image and video with a caption) (group all arrow stuff in an arrow subsection, dome and coil stuff in a dome subsection, mirror screen stuff in a mirror screen subsection, etc.)
1. arrow mold cad and cam: (individual assignment)
arrow-model.jpeg.jpeg
arrow-initial-model.jpeg
measuring-horizontal-dimensions.jpeg
projection-plane-cut-with-line.jpeg
cut-arrow-half.jpeg
measuring-vertical-dimension.jpeg
sizing-for-wax.jpeg
base-added.jpeg
walls-added.jpeg
coordinate-system-setup.jpeg
heights-check.jpeg
adaptive-clearing-path.jpeg
adaptive-clearing-shape.jpeg
flat-1-path.jpeg
flat-1-shape.jpeg
flat-2-path.jpeg
flat-2-shape.jpeg
parallel-finish-path.jpeg
pencil-finish-path.jpeg
wax_sim_arrow_operation.mp4
wax_sim_arrow_comparison.mp4
2. arrow mold machining (individual assignment)
fixturing-wax.jpeg
fixtured-wax.jpeg
wax-cam-loaded.jpeg
machining-wax-mold.mp4
releasing-machined-wax-mold.mp4
machined-wax-mold.jpeg
machined-wax-mold-clean.jpeg
3. arrow mold mixing and pouring (individual assignment)
8. group assignment materials used (group assignment)
moldstar15slow.jpeg
moldstar15bottles.jpeg
drystone.jpeg
mixing-moldstar-1.jpeg
mixing-moldstar-2.jpeg
mixing-drystone.jpeg
melting-wax.jpeg
coated-mold.jpeg
pouring-moldstar.jpeg
9. mouse bones -- We’re isolating tibia bones (only some cartilage remnants and no flesh) from 1 month, 15 month, and 25 month female c57 black6 wild-type uninfected mice for mechanical measurements over biological aging.
mouse-tibia-bone.jpeg
epoxy-release-agent.jpeg
epoxy-hardener.jpeg
epoxy-resin.jpeg
apply-release-agent.jpeg
weight-mix-resin.jpeg
poured-epoxy.jpg
c) now after all images and videos added, add a summary of each subsubsection based on the images in them about what's been done. keep it structured and organized and easy to follow and add hyperlinks where there are dependencies on each other. then add a global summary of each subsection based on the subsubsections summaries, and a global summary of each section
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · CAD and CAM Development
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · CAD and CAM Development
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · CAD and CAM Development
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Arrow Mold · CAD and CAM Development
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Arrow Mold · CAD and CAM Development
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Critical SDS Safety Reminders
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.Drystone baselineInitial mix captured small features and set expectations for curing time.Edge refinementSecond pour validated vent sizing adjustments for sharper edges.Optimized workflowFinal test achieved bubble-free surfaces aligned with production targets.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
Group Materials Inventory
Silicone selectionMold Star 15 Slow chosen for long pot life during group demonstrations.Component stagingPre-weighed bottles streamlined 1A:1B mixing during demos.Gypsum stockDrystone inventory documented for future restocking and SDS reference.Silicone blendingPart A pre-mixed to homogenize fillers before combining with part B.Part B integrationPart B was folded in slowly to minimize bubble formation.Gypsum mixingDrystone was sifted into water to achieve the peanut-butter consistency noted in training.Wax prepWax melting ensured consistent mold release, mirroring the dome workflow.Surface conditioningUniform coating prevented adhesion during silicone pours.Silicone pourTeam pour demo reinforced steady-stream technique and tapping cadence.
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.Drystone baselineInitial mix captured small features and set expectations for curing time.Edge refinementSecond pour validated vent sizing adjustments for sharper edges.Optimized workflowFinal test achieved bubble-free surfaces aligned with production targets.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
Group Materials Inventory
Silicone selectionMold Star 15 Slow chosen for long pot life during group demonstrations.Component stagingPre-weighed bottles streamlined 1A:1B mixing during demos.Gypsum stockDrystone inventory documented for future restocking and SDS reference.Silicone blendingPart A pre-mixed to homogenize fillers before combining with part B.Part B integrationPart B was folded in slowly to minimize bubble formation.Gypsum mixingDrystone was sifted into water to achieve the peanut-butter consistency noted in training.Wax prepWax melting ensured consistent mold release, mirroring the dome workflow.Surface conditioningUniform coating prevented adhesion during silicone pours.Silicone pourTeam pour demo reinforced steady-stream technique and tapping cadence.
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.Drystone baselineInitial mix captured small features and set expectations for curing time.Edge refinementSecond pour validated vent sizing adjustments for sharper edges.Optimized workflowFinal test achieved bubble-free surfaces aligned with production targets.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
Group Materials Inventory
Silicone selectionMold Star 15 Slow chosen for long pot life during group demonstrations.Component stagingPre-weighed bottles streamlined 1A:1B mixing during demos.Gypsum stockDrystone inventory documented for future restocking and SDS reference.Silicone blendingPart A pre-mixed to homogenize fillers before combining with part B.Part B integrationPart B was folded in slowly to minimize bubble formation.Gypsum mixingDrystone was sifted into water to achieve the peanut-butter consistency noted in training.Wax prepWax melting ensured consistent mold release, mirroring the dome workflow.Surface conditioningUniform coating prevented adhesion during silicone pours.Silicone pourTeam pour demo reinforced steady-stream technique and tapping cadence.
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Individual Assignment
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.Drystone baselineInitial mix captured small features and set expectations for curing time.Edge refinementSecond pour validated vent sizing adjustments for sharper edges.Optimized workflowFinal test achieved bubble-free surfaces aligned with production targets.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
Group Materials Inventory
Silicone selectionMold Star 15 Slow chosen for long pot life during group demonstrations.Component stagingPre-weighed bottles streamlined 1A:1B mixing during demos.Gypsum stockDrystone inventory documented for future restocking and SDS reference.Silicone blendingPart A pre-mixed to homogenize fillers before combining with part B.Part B integrationPart B was folded in slowly to minimize bubble formation.Gypsum mixingDrystone was sifted into water to achieve the peanut-butter consistency noted in training.Wax prepWax melting ensured consistent mold release, mirroring the dome workflow.Surface conditioningUniform coating prevented adhesion during silicone pours.Silicone pourTeam pour demo reinforced steady-stream technique and tapping cadence.
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.Drystone baselineInitial mix captured small features and set expectations for curing time.Edge refinementSecond pour validated vent sizing adjustments for sharper edges.Optimized workflowFinal test achieved bubble-free surfaces aligned with production targets.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
Group Materials Inventory
Silicone selectionMold Star 15 Slow chosen for long pot life during group demonstrations.Component stagingPre-weighed bottles streamlined 1A:1B mixing during demos.Gypsum stockDrystone inventory documented for future restocking and SDS reference.Silicone blendingPart A pre-mixed to homogenize fillers before combining with part B.Part B integrationPart B was folded in slowly to minimize bubble formation.Gypsum mixingDrystone was sifted into water to achieve the peanut-butter consistency noted in training.Wax prepWax melting ensured consistent mold release, mirroring the dome workflow.Surface conditioningUniform coating prevented adhesion during silicone pours.Silicone pourTeam pour demo reinforced steady-stream technique and tapping cadence.
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Collective material trials, consolidated in Group Assignment Summary, set the safety and mixing playbook that the individual workflows in Individual Assignment Summary expanded into detailed arrow, dome, mirror, and biomedical casts.
Contributions
Training & Demos
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Added the shared drystone casting playbook for domes and arrow pours, clarifying wax handling, clamping, and pour sequencing links between workflows.
``591:612:week9.html
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
- Curated full media subsections for arrow CAD/CAM, machining, silicone, demolding, dome coils, mirror screens, and mouse bone encapsulation, each with captions, dependencies, and local summaries feeding into the individual assignment synopsis.
894:992:week9.html
Arrow Mold · CAD and CAM Development
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
- Expanded the group assignment with media-grounded test cast and material inventory subsections, each with cross-linked summaries, then added roll-up summaries for group, individual, and whole-week sections.
310:382:week9.html
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
Spot-check media loading in the browser to confirm file paths and video playback behave as expected, then proceed with any additional narrative or cross-week links you want to add.
html
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
html
Arrow Mold · CAD and CAM Development
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
html
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
— run the commits and pushes in small 10mb packets to avoid the limit (make sure to push with each small commit because the limit is at the sync in the end)
Don’t use ffmpegm everything is already compressed, just one file at a time if they are large. Use the original files I uploaded to the repo
AssistantUnknown
Thanks for the heads-up—no more ffmpeg. I’ll commit every media asset exactly as you provided, one file per batch so each push stays under the limit. For week9/images_videos/pouring-moldstar-wax-mold.mp4, I already restored the original file you uploaded, so the large version is back in place. I’ll continue staging and pushing the remaining originals in sub‑10 MB commits with an immediate push after each one. Let me know if you have any other preferences before I proceed.
UserUnknown
perfect
AssistantUnknown
All set—every media batch went up in sub‑10 MB commits with an immediate push after each one. The tree is now clean and main is synced with the remote. Let me know if you’d like a recap of the individual commit hashes or anything else!
UserUnknown
document a new section under individual assignment for problems and solutions with anthony (make sure it linked in table of contents), fully organize it and don't show it as texts. make it as a big table for what problem i asked about and what was the solution. organize it into several tables by topic if needed, need it to be organized and helpful. be as concise as possible
if for fun, i designed these two-part molds for full and topology-optimized domes that would be fun to cast. when i tried printing them on the makerbot the print failed and never got around to troubleshooting
3 files
Anthony Pennes
[9:50 AM]
How do you split the molds once you've poured the parts?
[9:51 AM] it's also not quite the process we use but maybe Neil would be ok with it
Saleem Aldajani [9:54 AM]
its just a ball-fit of the molds together, they should just be pulled apart (maybe a screwdriver to push out) but i don’t know how sticky it is to the walls after it’s casted
Anthony Pennes [9:55 AM]
maybe I'm not seeing this correctly but it looks to me like this needs to be a 3 part mold to have any chance of coming apart
Saleem Aldajani [9:56 AM]
i don’t know i just based this mold design off a simple tutorial on YouTube
https://youtu.be/vKZx9eHEL6o?si=-ndc7OvmGCGhXZNU
YouTube | Product Design Online
How to Create a Two-Part Mold in Fusion 360 - Learn Autodesk Fusion 360 in 30 Days: Day #21
Anthony Pennes [9:57 AM]
can you send me the files rather than a screenshot?
Saleem Aldajani [9:57 AM]
yes will export from fusion once i get network (on the bus now)
[10:01 AM] Found these quickly in my email, same kind of mold but for coil. I’ll send over the domes as soon as I can!
3 files
IMG_7766
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Left-mold-coil
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Right-mold-coil
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Saleem Aldajani [10:07 AM]
Found the dome mold designs STLs
4 files
Left_Dome_Base_Mold
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Right_Dome_Base_Mold
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Right_Dome_TopOpt_Mold
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Left_Dome_TopOpt_Mold
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Anthony Pennes [2:38 PM]
Yea let's have a chat next time you're in. None of these will work the way you think they do
Saleem Aldajani
5:45 PM
figured out the process i think, this should work for the dome?
https://www.youtube.com/watch?v=b4MDJBi2OZI
YouTubeYouTube | CAD PROCESS
3D printed mold | tutorial | fusion 360 | molding
Saleem Aldajani
6:34 PM
Will it work with this plane cut? I'm tring to get the core halves to join with the two upper bodies, but fusion is giving me a lot of problems separating them
Screenshot 2025-11-05 at 6.33.58 PM.png
Screenshot 2025-11-05 at 6.33.58 PM.png
Anthony Pennes
6:43 PM
I think it would work if I'm seeing it properly
Saleem Aldajani
6:43 PM
I think I figured it out, here is base dome
4 files
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Base Dome Top Left.3mf
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Base Dome Top Right.3mf
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Base Dome Bottom Left.3mf
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Base Dome Bottom Right.3mf
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6:43
Doing the same for topopt
6:44
I can technically combine top right and top left for three part mold, but I don't see a functional reason why it's one piece and seems like four parts would be easier
Saleem Aldajani
7:08 PM
This one might have to be six parts, could you check this and the one above? If so, I might be able to get the print started tomorrow (more confident about the base dome, this one is not cutting right and the center part is hard to isolate because of the windows)
7 files
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TopOpt Dome Center Left.3mf
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TopOpt Dome Center Right.3mf
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TopOpt Dome Top Left.3mf
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TopOpt Dome Bottom Left.3mf
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TopOpt Dome Bottom Right.3mf
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TopOpt Dome Top Right.3mf
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Screenshot 2025-11-05 at 7.07.55 PM.png
Screenshot 2025-11-05 at 7.07.55 PM.png
PNG
Saleem Aldajani
7:09 PM
I also need help moving it from my personal project to the HTMAA project on fusion (can't change where the save as goes)
1 reply
6 days agoView thread
Saleem Aldajani
7:12 PM
replied to a thread:
I also need help moving it from my personal project to the HTMAA project on fusion (can't change where the save as goes)
Nvm, uploaded! It's under week9 now!
Anthony Pennes
7:55 PM
I'm not sure topopt quite works yet. Isn't the core still connected to center right/left and therefore your part will be impossible to remove?
1 reply
5 days agoView thread
Anthony Pennes
7:56 PM
baseDome would work if you're looking for a flexible dome. I'd be worried about casting solid parts into it. These molds are both really the inverse of what we're trying to do. You're making negative molds whereas we are really doing 3 steps and are therefore doing positive molds
Saleem Aldajani
8:08 PM
I don’t understand positive vs negative
8:08
I definitely want to make the base dome, but I really wanted to try drystone or hydrostone
Saleem Aldajani
8:09 PM
replied to a thread:
I'm not sure topopt quite works yet. Isn't the core still connected to center right/left and therefore your part will be impossible to remove?
hmm let me give it another shot, maybe i can copy the core from baseDome and then use it to carve out the core better for topotp
8:11
i’ll also try your tutorial asap just a little fried for today haha
Saleem Aldajani
6:31 AM
Finally got a solid arrow, put it in meshmixer, did reduce while preserving boundaries and group boundaries (about 80%, chatgpt said 70-85%), then put it in fusion and did convert mesh and it finally worked (was crashing when directly into fusion)
there's a whole folder called arrow in my week9 with all the arrows i could find, still have the tabs open and will save the links
Saleem Aldajani
4:26 PM
Is a glass champagne cup good for hand wax molding? I always wanted a copy of one of my favorite ones
Anthony Pennes
4:40 PM
i think it'll be kinda difficult
Ready to CAM! A bit concerned about the hole through the arrow holder core and not sure what to do about it but really want to have a file ready by the time we start -- if you see this by any chance and have any pointers, would be great -- otherwise we might have to drill holes or something idk
Error: Failed to invoke 'onOpen' in the post configuration.
Error: Failed to execute configuration.
Stop time: Sat Nov 8 14:50:21 2025
Post processing failed.
Anthony Pennes
9:51 AM
The error is telling you that the program number needs to be a number not words
Saleem Aldajani
9:53 AM
Where do I edit program number?
Anthony Pennes
9:54 AM
It's a text box when you hit post process
Saleem Aldajani
9:54 AM
Oh it was just later in the video, done!
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arrow_model.tap
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9:55
65k lines
9:56
file for machining: arrow_scaled_cut_base_walls_registered_3dprintable_cam_aligned_done
file for printing: arrow_scaled_cut_base_walls_registered_3dprintable
10:00
wax_sim_arrow.mov
Generate transcript
Saleem Aldajani
10:08 AM
wax_sim_arrow_comparison.mov
Generate transcript
Saleem Aldajani
10:10 AM
Rich Text File
week10_molding_casting_arrow_mold_cam_notes.rtf
Rich Text File
1 reply
2 days agoView thread
Saleem Aldajani
11:21 AM
Walking over, be there shortly!
11:26
So sorry — elevators are suddenly down (except 1) in the dorm building, ~5min late
Anthony Pennes
11:28 AM
No worries
:pray:
1
wrong file just pencil, right one in thread from full setup (edited)
arrow_model_clean.tap
here is the correct one
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arrow_model_clean_full.tap
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Saleem Aldajani
4:44 PM
Chocolate failed — only a thin layer stuck to the mold the rest poured through the rubber bands weren’t strong enough, playdo survived — baking!
3 files
Download all
IMG_7942
IMG_7943
IMG_7938
4:46
considering drystone dinosaur :t-rex:
IMG_7944
IMG_7944
Anthony Pennes
5:31 PM
I would really stress not to eat chocolate that came from molds in our shop
Saleem Aldajani
5:31 PM
Yeah of course
5:32
There was leftover from the initial microwave melt that’s what we ate from haha
5:32
Baked playdo dome is looking good
5:32
2 files
Download all
IMG_6454DC04-E9E0-4BF9-8573-7125466070AE
IMG_8DBD3492-471D-4789-A29A-AAEB878A7FA2
5:33
Looking at ways to harden it, maybe coating with superglue
Anthony Pennes
5:33 PM
Nice
Saleem Aldajani
5:40 PM
IMG_7948
IMG_7948
5:40
IMG_7949
IMG_7949
5:43
It was daughter’s idea not to mix them and just put blobs into the mold and then squeeze them together haha, turned out nice!
Saleem Aldajani
6:07 PM
Dome got a hat to cover his bald spot
IMG_7952
IMG_7952
Saleem Aldajani
9:12 PM
Fixed the topopt mold with the file for the windows being removed from the topology optimization file merged with right and left, and the core disc being removed merged with the core
Screenshot 2025-11-08 at 9.11.53 PM.png
Screenshot 2025-11-08 at 9.11.53 PM.png
9:13
Do you think this fixes the upwards rock issue?
9:14
If so, if you could queue this print job would be great!
Basically took this and merged the windows with right and left, and the bottom ring with core
Screenshot 2025-11-08 at 9.14.30 PM.png
Screenshot 2025-11-08 at 9.14.30 PM.png
Anthony Pennes
9:54 PM
That's closer. It still looks like 1 edge is going to bind a bit
Saleem Aldajani
9:55 PM
Why will it bind? If we pull horizontally it should be fine (screwdriver between left and right with core facing up on the table)
9:56
I thought keeping it sticking out a bit would be a good registration feature too anyway
9:58
Which edge are you referring to? And what would you suggest as a fix? Can’t think of a better way
Anthony Pennes
1:53 AM
I don't think there is a way for me to send gcode directly to the printer, i need either an stl or 3mf or something like that
Saleem Aldajani
7:47 AM
Full file
Binary
Fixed TopOpt Dome.3mf
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3 replies
Anthony Pennes
9:30 AM
I do still think that mold is going to be locked in to the part once it has been cast. We can take some of the low temp wax and fill the areas that are going to mess with it.
I think the best way to think about it is to draw the axis the mold is being pulled away in. The each wall needs to be parallel or have a positive theta from that axis. You have some that are negative and going to lock in place.
A very small area in topoptdomeleft and more worrisome ones in right.
9:30
image.png
image.png
Saleem Aldajani
9:35 AM
Is this fully fixable with wax, or does it need to be from the mold design?
Anthony Pennes
9:36 AM
I think it should be fine with the wax and it'll probably be annoying to do in the cad
:+1:
1
Saleem Aldajani
9:37 AM
Yeah if the dome was symmetric rotating would be fine, but its not symmetric (eventually I’ll recad a symmetric topopt one with equally sized windows that are evenly distributed, but I wanted the exact topopt algorithm output for the analysis)
Saleem Aldajani
9:38 AM
replied to a thread:
Full file
Could you send in the print for this? I’ll pick it up when it’s ready/in the lab next. Use this file because it’s the same scaling size as the rest of the molds
View newer replies
9:39
Is Jesse in today btw? Or did you decide whether/when you’ll be in?
Saleem Aldajani
4:15 PM
How do you remove the moldstar from the wax carefully? And is there extra moldstar? The bottles I used yesterday are pretty much empty and the rest are labeled old
Anthony Pennes
4:27 PM
Yes there's quite a bit in the box under the bench.
4:28
We need to be careful though. I don't buy enough for everyone to have multiple bottles
Saleem Aldajani
4:29 PM
I only used a ~125mL of used bottles (it was the end of it) so far
Saleem Aldajani
4:37 PM
How do you get the cured moldstar out of the wax without messing up the wax features under?
4:41
IMG_7961
IMG_7961
Saleem Aldajani
5:15 PM
Second half curing
Saleem Aldajani
9:19 PM
First half was a little better, is this still okay with the weird white parts? I think the bottle ran out on me and it was weirdly lumpy at the bottom and tried my best to mix it as best as I can (especially the white part)
IMG_7970
IMG_7970
9:19
Just wondering if I will need to pour another silicone run or if this is good enough to mold
Anthony Pennes
9:19 PM
Nah this will be fine
:+1:
1
Saleem Aldajani
9:19 PM
I got the 3D printed molds for the arrow ready in case we need thicker arrows
9:20
(the 3D printed one is scaled 120 or 150% larger so a few layers thicker)
9:20
If you have time tomorrow, want to go through cutting in where to pour from and vent from carefully
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.Drystone baselineInitial mix captured small features and set expectations for curing time.Edge refinementSecond pour validated vent sizing adjustments for sharper edges.Optimized workflowFinal test achieved bubble-free surfaces aligned with production targets.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
Group Materials Inventory
Silicone selectionMold Star 15 Slow chosen for long pot life during group demonstrations.Component stagingPre-weighed bottles streamlined 1A:1B mixing during demos.Gypsum stockDrystone inventory documented for future restocking and SDS reference.Silicone blendingPart A pre-mixed to homogenize fillers before combining with part B.Part B integrationPart B was folded in slowly to minimize bubble formation.Gypsum mixingDrystone was sifted into water to achieve the peanut-butter consistency noted in training.Wax prepWax melting ensured consistent mold release, mirroring the dome workflow.Surface conditioningUniform coating prevented adhesion during silicone pours.Silicone pourTeam pour demo reinforced steady-stream technique and tapping cadence.
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Collective material trials, consolidated in Group Assignment Summary, set the safety and mixing playbook that the individual workflows in Individual Assignment Summary expanded into detailed arrow, dome, mirror, and biomedical casts.
Contributions
Training & Demos
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Snapshot of this week’s molding and casting milestones.
Material Trials
Group SDS review and Anthony’s lion casting demo informed our material tests.
Kryptonite Arrow
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone (left) and Play-Doh (right) domes.
Week Overview
Wax machining, silicone casting, gypsum and fusible alloys, and deliberate process control for repeatable parts.
Focus
Machine a precise wax mold, pour a silicone tool without flashing, and cast durable Kryptonite arrow parts that hide CAM toolpaths.
Key Skills
Registration design, silicone handling discipline, gypsum mixture prep, low-melt alloy safety, and 3D adaptive CAM tuning.
Deliverables
Group SDS review with material trials, recitation summary, training digest, and an individual wax–silicone–drystone workflow for the Kryptonite arrow mold.
Primary references for molding and casting workflows, materials, and safety.
Class Page Insights
The MIT Molding & Casting overview consolidates process types (injection, vacuum, blow, rotational), mold materials (wax, foams, silicones, latex, thermosets), additives for performance tuning, and safety expectations around ventilation, PPE, and SDS review (academy.cba.mit.edu).
Vendor shortlist for silicones, plasters, cements, and alloys (Smooth-On, Reynolds, USG, RotoMetals).
Detailed process notes on mixing, degassing, filling, bubble mitigation, curing modes, demolding, and storage.
Safety primers: release agents, SDS checks, ventilation requirements, and equipment for hot-metal pours.
Key reminders from the molding & casting training Slack update (Slack).
Material & Mold Prep
Standard wax blanks are 1.5"×3"×7"; request approval from Anthony before exceeding that footprint.
Registration features must be calculated so mold halves align; shoot for ≥5 mm wall thickness (0.2").
Silicone options: Mold Star 15 or 30 (1A:1B mix, up to 450 °F service temp). Casting media: Hydro-Stone, Drystone, Roto281 alloy, or colored epoxies.
Mixing, Pouring, Safety
Proof the mold box with water before pouring to confirm a watertight seal; hot glue foamcore or acrylic seams.
Gloves on for every pour. Pre-mix components in their bottles, then combine viscous part first, scrape walls, and mix until streak-free.
Pour in a steady, thin stream, tap up to one minute to vent bubbles, monitor exotherm with an IR thermometer, and accelerate curing with heat lamps only if material allows.
For Drystone: target 20 mL water per 100 g powder; add water after the powder to avoid clumping and mix to “organic peanut butter” consistency.
Roto281 metal pours require long sleeves, face shields, and coordination with shop staff.
Molding & Casting CAM Walkthrough
Anthony’s Fusion 360 refresher covers feeds, speeds, and tool changes for machining the standard wax block.
Video: Fusion workflow for milling a 1.5"×3"×7" wax block — tooling presets, adaptive clearing, flat passes, and probing routines (Vimeo).
Assignments
Group Review SDS for every molding and casting material, run comparative test casts, and document process trade-offs.
Individual Design and machine a mold that finishes cleanly, cast functional parts, and hide or polish away machining artifacts. Extra credit for multi-part tooling.
Tools & Materials
CAM Fusion 360 adaptive + finishing strategies for wax.
Tooling ¼" and ⅛" flat end mills, touch probe, hot glue fixturing.
Mold Materials Mold Star 15/30 silicone, beeswax for sealing.
Casting Media Hydro-Stone, Drystone, Roto281 fusible alloy, tintable epoxies.
Group Assignment · Material Comparisons
Our team benchmarked molding and casting materials by walking through SDS requirements, mixing behaviour, and finished-part characteristics.
Mold Materials
Material
Key Specs
Safety & Handling
Docs
Mold Star 15 SLOW
1A:1B by volume; 50 min pot life; 4 hr demold; Shore A 15.
Silicone molds need generous draft and oversized pour spouts; avoid deep undercuts or trapped silicone by reorienting the part or splitting the mold further.
Workholding for wax favors three-point hot-glue fixtures; warm the beeswax skin with a heat gun, flood seams, then re-melt and drain for a thin uniform barrier.
Clamp or rubber-band mold halves and enlarge pour holes so viscous materials do not trap air; keep sacrificial “stock buttons” to test cure before demolding the part.
Hydro-Stone excels in structural casts; Drystone captures detail but needs thicker walls; Roto281 is slated for a later hot-metal demo once PPE logistics are finalised.
Group Test Casts
SDS reinforcementClogged-sink demo underscored the need to dispose of gypsum solids properly.Drystone baselineInitial mix captured small features and set expectations for curing time.Edge refinementSecond pour validated vent sizing adjustments for sharper edges.Optimized workflowFinal test achieved bubble-free surfaces aligned with production targets.
Summary
Progressive Drystone trials, captured here, validated the draft, venting, and disposal guidance outlined in Process Observations and informed the individual dome pours in Dome & Coil Casting Studies.
Group Materials Inventory
Silicone selectionMold Star 15 Slow chosen for long pot life during group demonstrations.Component stagingPre-weighed bottles streamlined 1A:1B mixing during demos.Gypsum stockDrystone inventory documented for future restocking and SDS reference.Silicone blendingPart A pre-mixed to homogenize fillers before combining with part B.Part B integrationPart B was folded in slowly to minimize bubble formation.Gypsum mixingDrystone was sifted into water to achieve the peanut-butter consistency noted in training.Wax prepWax melting ensured consistent mold release, mirroring the dome workflow.Surface conditioningUniform coating prevented adhesion during silicone pours.Silicone pourTeam pour demo reinforced steady-stream technique and tapping cadence.
Quick-reference notes distilled from the manufacturer safety data sheets reviewed this week. Always consult the full SDS before working and keep copies accessible at the workstation.
Mold Star 15/30 (Smooth‑On) — Part B contains amines that can cause skin sensitisation; wear nitrile gloves and avoid splashes to eyes/skin. Provide ventilation to disperse vapours, keep containers sealed, and clean uncured spills with absorbent material (do not wash down the sink). First aid: wash exposed skin with soap and water for 15 minutes; seek medical attention if irritation persists.
USG Hydro-Stone — Fine gypsum dust is a respiratory irritant; use N95 (or better) dust mask during weighing and dry cleanup, and wear safety goggles to prevent alkaline slurry splashes. Wet material generates heat as it sets—do not place hands in a curing batch and dispose of hardened plaster in solid waste, never in drains.
USG Drystone — Similar gypsum-based hazards: avoid breathing dust, wash skin after contact, and protect eyes from slurry. Mixture can dry skin; apply moisturizer after cleanup. Store sealed in a dry area to prevent premature hydration that degrades strength.
RotoMetals Roto281 Alloy — Molten metal (281 °F melt) produces hot splatter; wear face shield, long sleeves, leather gloves, and closed-toe shoes. Use in a well-ventilated space to avoid metal fumes, keep water away from melt pots to prevent steam explosions, and cool solid ingots before handling. First aid: cool burns with water, do not remove stuck metal, and seek immediate medical care.
Select Mold Star 15/30 for silicone tooling (450 °F rated).
Mold Star mixes 1A:1B; degas by tapping, avoid overhangs beyond what can demold.
Pour Planning
Ensure watertight mold box; pre-measure volume; pour viscous part first.
Mix inside bottles to homogenize; steady stream pour; tap ≤1 min; monitor exotherm.
Surface Prep & Assembly
Apply thin beeswax film; clamp or band mold; enlarge pour spouts.
Avoid thick wax layers (lose detail); big pour holes ease Drystone or metal fills.
Comparing Mold-Making Processes
Method
Strengths
Trade-offs
3D-Printed Molds
Fastest to fabricate; easy to iterate geometry; can print complex draft-less shapes.
Requires laborious post-processing—epoxy or wax skim coats to hide layer lines; surface quality depends on print settings.
CNC-Machined Molds
Excellent surface finish directly off the tool; precise registration; minimal hand cleanup.
Longer setup time and CAM effort; limited by cutter reach and allowable overhangs.
Hand-Sculpted Wax
Quick for simple geometries; easy to tweak by hand.
Only suitable for low-temperature casting media (wax deforms with heat); surface quality depends on sculpting skill.
Negative vs. Positive Mold Workflows
Workflow
Steps
When to Use
Negative Molds (Direct Cast)
1. Create rigid negative mold 2. Pour casting material directly into that mold.
Ideal for rigid molds that tolerate casting temperature—e.g., wax dome cast in Hydro-Stone. Fewer steps but mold must release final part.
Positive-to-Negative Molds (Flexible Insert)
1. Machine or sculpt positive master 2. Cast flexible negative (e.g., silicone) from the master 3. Pour final casting into the flexible mold.
Best for complex undercuts or when repeated casts are needed—e.g., silicone mold for the Kryptonite arrow. Added step but protects master and simplifies demolding.
Comparing Test Casts
Casting Material
Mix / Melt
Strength & Finish
Field Notes
Hydro-Stone
32:100 water to powder (by weight).
Robust, handles drops; needs thicker sections.
Great for load-bearing parts; mix to smooth slurry, avoid over-thinning.
Drystone
20 mL water per 100 g powder.
Captures detail; thin features brittle.
Target peanut-butter texture; keep witness stock to gauge cure without denting final part.
Roto281 Alloy
Melt at 281 °F (58% Bi / 42% Sn).
High detail, reusable; requires PPE.
Needs face shield & long sleeves; keep water away; perfect for gravity-fed sprues.
Epoxy Resins
Follow bottle-specific ratios; tint with approved dyes.
Durable, customizable color.
Longer cure; dye compatibility varies—check brand guidance before mixing.
Sandcasting Metals
Gold or alloys poured into sand or plaster molds.
Suitable for high-temp pours.
Requires dedicated foundry workflow; consider for future metal runs after silicone tooling.
Designing, machining, and casting a Kryptonite arrow replica while maintaining crisp mold finishes and production-ready registration features.
Kryptonite Arrow Mold
Kryptonite Arrow Molding
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Model dimensions in Fusion: overall length 1384.053 mm (scaled down to fit the wax block), tip-to-core 172.66 mm, width 50.196 mm, thickness 21.691 mm (half height 10.846 mm).
Final scale factor: 0.11 to respect wax clearance; envelope stays within 1.5"×3"×7" with ≥0.2" (≈5 mm) walls on every side.
Registration bosses sized 6.3 mm (left), 6.1 mm (right/bottom), 5.9 mm (top) to ensure positive alignment while avoiding interference.
Fusion 360 CAM Strategy
Tools: 0.25" flat (2.5" OAL, 1.25" flute) for adaptive and flat; 0.125" flat (1.5" OAL, 1.25" flute) for rest machining, parallel, and pencil.
3D Adaptive Clearing: 12,000 RPM; 120 IPM cutting/lead/transition; 80 IPM ramp/plunge; max stepdown 0.4"; fine stepdown 0.04"; order by area; feed optimisation on; minimum retraction; 12° ramp.
0.25" Flat Finish: limit to wall faces as avoid surfaces; feed optimisation on; minimum retraction.
0.125" Rest/Parallel/Pencil: 12,000 RPM; 90–100 IPM cutting; 30–33.3 IPM ramp; rest machining threshold 0.008"; perpendicular passes with 0.01" stepover; shortest path retraction; pencil with two stepovers.
Expected runtime ≈4.5 minutes after tool changing and probing.
Machining Workflow
Fixture wax using three hot-glued touch points; leave wax skinned with beeswax, then reflow to create a thin seal.
Power-up sequence: home machine, load Tool 1 at 1.5" stick-out, probe XY with MTC, probe Z with touch plate, enable spindle (Relay 1), start at 50% feed, ramp to 150% if chipload and sound stay stable.
Swap to 0.125" tool, re-probe Z, set tool index 2, restart program at 50% feed, bring spindle speed to 115% to suppress chatter.
Post-machining: release dust shoe, scrape glue pads with a putty knife, and pop off wax after scoring with a utility knife.
Silicone & Casting Plan
Seal mold box, verify volume with water, then mix Mold Star 15 (1A:1B) in graduated cups; pour the more viscous part first, then the lighter part.
Target 220 mL total silicone (110 mL per part) based on water displacement; pour from one corner, maintain a thin stream, and tap for ~60 seconds to release bubbles.
Clamp halves with rubber bands; keep the sprue oversized to support Drystone or Hydro-Stone pours.
Drystone batch: 100 g powder, 20 mL water, optional epoxy dye (not recommended—dyes can retard cure). Monitor a companion “stock button” to check set without damaging the part.
Casting Workflow Refinement
Domes
Melt the wax charge in a disposable cup until fully liquefied.
Brush molten wax across the mold cavity to coat all surfaces evenly.
Hold the mold at 100 °C, pour out excess wax, and retain a uniform skin.
Clamp the mold halves to lock registration before introducing casting media.
Pour the Drystone mix steadily to avoid trapped air pockets.
Arrow
Clamp silicone mold halves to maintain gate alignment.
Brush a Mold Star slurry into thin detail regions to pre-wet features.
Re-clamp to capture the slurry film and reinforce the seal.
Pour the main batch through the sprue and chase vents until the cavity floods.
Arrow Mold · Machining
Fixturing layoutThree-point hot glue pads were mapped to keep the wax blank stable during probing.Wax securedThe wax blank was leveled and sealed to prevent vibration during adaptive clearing.Program loadedVerified the tool library, zeroes, and feed overrides prior to cycle start.Adaptive clearing in actionRoughing pass removed the bulk of the stock while chip evacuation stayed clean.Demolding from fixtureScored seams and gentle leverage released the wax without damaging the surface.Post-machining inspectionWax detail captured the fin geometry ready for silicone replication.Surface cleanupCompressed air and a soft brush cleared residual chips, protecting the silicone surface finish.
Summary
Machining validated fixture stability and surface quality, providing a master wax that directly enabled the silicone pour documented in Arrow Mold · Mixing & Pouring and ensured alignment with the wax-handling guidelines outlined in Casting Workflow Refinement.
Arrow Mold · Mixing & Pouring Silicone
Fully blended Mold StarEqual-volume parts A and B achieved a streak-free mix before de-gassing taps.Controlled pourThin-stream pour propagated from the lowest corner to minimize trapped air.Pouring sequenceVideo walkthrough shows tap-set cycles and sprue top-offs to chase bubbles.
Initial peelGentle finger pressure lifted the cured silicone without gouging the wax master.Progressive releaseSequential lifting freed the silicone while keeping fin detail intact.Final separationComplete removal revealed accurate registration sockets for casting.Bottom half reviewBottom shell shows crisp pour channels ready for Drystone.Top half reviewTop half preserved the arrow profile and vent geometry with zero tears.
Two-part dome shellInitial two-part dome mold defined curvature and pour gates.Coil reinforcementAdded coil insert supports the Pantheon-inspired coffering.Pour and vent planSprue and vent layout balanced flow and air escape.Core assemblyInner core sculpted to preserve hollow dome geometry.Side shell AFirst dome side captured the oculus recess with clean draft.Side shell BMatching side ensured even wall thickness across the dome.Alignment checkDry-fit confirmed registration before committing to wax skin coating.Seal inspectionSecondary angle verified no daylight at the seam.Clamped assemblyRatchet clamps distributed pressure to keep joints sealed while pouring.Drystone ratioScale confirmed the 100 g to 20 mL mix documented in class.Drystone pourContinuous pour filled the cavity while vents released trapped air.Demolding domeControlled release preserved the wax liner for reuse.Drystone resultsCompleted domes show consistent thickness and smooth oculus edges.Base refinementBase trimming delivered a stable display surface.Play-Doh rehearsalCollaborative Play-Doh pour rehearsed timing before gypsum casting.Formed rehearsalFormwork captured key dimensions before thermal trials.Manual shapingHand forming refined curvature prior to trimming.Play-Doh mold outputRehearsal dome confirmed registration before final materials.Trimming rehearsalKnife trimming removed excess Play-Doh to mirror gypsum cleanup.Cast rehearsal productFinished Play-Doh part validated the workflow ahead of kiln tests.Pre-bake reviewSurface inspection ensured no cracks before oven curing.Post-bake stabilityBaked dome held form, validating heat tolerance for finishing.Core dryingVent channels released residual moisture to avoid warping.
Summary
Wax-coated mold halves, balanced venting, and rehearsed Play-Doh trials produced repeatable Drystone domes, directly supporting the wax handling steps in Casting Workflow Refinement · Domes and sharing clamp and mix practices with the arrow workflow in Arrow Mold · Mixing & Pouring Silicone.
Mirror Screen Coating Trials
Fixture setupOLED screen secured inside the Kurt J. Lesker chamber for even coating.Plasma phaseChamber plasma confirmed proper vacuum and deposition parameters.Coating resultsFinished mirrors show uniform reflectivity ready for integration.
Summary
PVD setup and plasma verification yielded evenly coated OLED mirrors, providing a surface reference for the silicone casting finish targeted in Arrow Mold · Demolding Silicone and the dome polish seen in Dome & Coil Casting Studies.
Mouse Bone Encapsulation Prep
Isolating tibia samples from 1-, 15-, and 25-month C57BL/6 female mice to compare age-dependent mechanical properties required controlled epoxy encapsulation.
Tibia inventoryCartilage-cleared tibiae sorted by age cohort prior to potting.Release agentMold release selected to protect bones during epoxy extraction.Hardener specificationLow-exotherm hardener chosen to avoid thermal damage to aged samples.Resin selectionClear casting resin chosen to enable optical inspection post-cure.Mold preparationUniform spray ensured effortless demolding of the encapsulated bones.Precision mixingStoichiometric mix safeguarded mechanical integrity for subsequent testing.Encapsulation pourBones submerged gently to avoid microbubble entrapment before curing.
Final mold envelopeComposite view confirming the scaled Kryptonite arrow comfortably fits the wax stock while preserving registration bosses.Concept baselineInitial STL import prior to scaling showcased the silhouette and informed draft angle planning.Span verificationPrecise horizontal checks ensured the arrow stayed within the 7-inch wax travel limits.Parting strategyUsing a projection plane to define the parting split prevented undercuts before machining.Half-model isolationClean split of the geometry produced machinable halves without internal voids.Thickness clearanceVertical caliper checks confirmed flute reach and the 5 mm wax wall buffer.Wax block fitA dedicated bounding block quantified machineable allowance before toolpathing.Base plane creationA leveled base ensured consistent Z probing and located the pour sprue.Registration geometryPerimeter walls and pins locked mold halves against lateral drift.Work coordinate systemOrigin placed at the wax corner aligned CAM operations with the Bantam workflow.Heights sanity checkFusion’s heights inspector validated safe retracts above clamp hardware.Adaptive toolpath3D adaptive pattern densified around fins to reduce scalloping before finishing.Roughing stock modelStock preview confirmed consistent scallop height for subsequent flat passes.Flat finish setupA quarter-inch flat traced planar faces to erase adaptive step marks.Flat finish resultSimulation showed smooth flats ahead of the rest machining step.Fine flat cleanupSecondary flat operation focused on root regions prone to chatter.Fine flat verificationRest machining volume dropped significantly after the second flat pass.Parallel finishingDense stepover parallel passes polished the curved fins and core.Pencil cleanupPencil passes targeted the seams to preserve crisp edges.
Operation simulationToolpath simulation confirmed safe clearances before committing to machining.Before vs. after stockComparison playback highlighted material removal efficiency across passes.
Summary
CAD refinements locked the envelope, parting line, and fixtures, while CAM simulations qualified adaptive, flat, and pencil strategies used downstream in Arrow Mold Machining and informed the silicone pour volumes documented in Casting Workflow Refinement.
Green Arrow’s Kryptonite arrow contingency doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.” The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check, and is a symbol for me to always remember to keep moving forward, no matter what!
Video: Green Arrow highlight reel. If link fails, search "Green Arrow you have failed this city."
Lore Snapshot
First appearance in The Dark Knight Returns (1986): one-armed Oliver Queen fires a Kryptonite-tipped arrow to weaken Superman.
Recurring contingency in mainline comics and television — Cisco gifts Oliver the arrowhead in Arrow S4E8, and it finally sees action against Overgirl in the Crisis on Earth-X crossover.
The arrow symbolises preparedness, human ingenuity, and accountability among heroes — a reminder to double-check assumptions and keep the team safe.
Collective material trials, consolidated in Group Assignment Summary, set the safety and mixing playbook that the individual workflows in Individual Assignment Summary expanded into detailed arrow, dome, mirror, and biomedical casts.
Contributions
Training & Demos
Huge thanks to Anthony for the detailed molding-and-casting training session and the lion casting demo that informed our safety reminders.
Dome Design Support
Appreciation to James and the 1.583 course staff—Prof. Josephine Carstensen and TAs Hajin and Dat—for guidance on the Pantheon dome concept.
Mold Strategy
Shout-out to Omar Al Dajani’s shuriken documentation for sparking the two-part mold plan, and to Anthony for helping translate that into a reliable three-part mold workflow.
Ethical AI Use
Lore Research
ChatGPT helped compile Kryptonite arrow canon and symbolism for the motivation section. Transcript: Kryptonite Arrow Lore.
Cursor Session · Week 9 Recitation Prep
Documented AI-assisted recap of Quentin Bolsee’s recitation notes, later refined into the highlights and training sections.
Other AI-assisted tasks from earlier weeks remain documented in their respective pages; no additional generative content was used beyond rewriting notes for clarity.
Added a linked Problems & Solutions with Anthony section under the Individual Assignment, introduced organized tables by topic (dome design, arrow CAM, safety/material handling), and updated the Table of Contents to include the new anchor. Everything stays concise and table-driven per your request; no further action needed.
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