— 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
tasks:
1. make a copy of week8.html and called it week9.html. make sure its linked on index.html. populate the relevant resources from https://academy.cba.mit.edu/classes/molding_casting/index.html
2. create recitation card with a refined version of these notes, link to slack message: https://mit-htmaa.slack.com/archives/C09AAU3RY9H/p1762470252921219
week 9 recitation how to make (almost) any machine
what is a machine — mechanism, actuation, automation (in general, motion platforms and end effectors)
machines used — digital, automatized, commoditized
computer numerical control
Cost of CNC mill today less than $1000, runs without a computer from microcontroller and SD card
digital fabrication led to fablab network
Exponential behavior enabled by automation, no longer need expertise in crafts to make physical objects
Making machines with the tools in a fablab, even more exponential and generate more fablabs
For example, prusa printer came from 3d printed 3d printer project
lifelong skills
Thinking of existing modules to create
for example, pen plotter
path planning for trajectories and actuation required for execution (read and make sense of the path for the machine)
motion platforms
stacked axes (wasteful, high mass — not speed it limits top acceleration), coreXY by Ilan Moyer (fastest e.g. prusa and Bambu), stewart platform (6 pistons for 6 dofs)
transform from motor coordinates to world coordinates (equations of motion)
end effectors
sand drawing, clay printing, light painting
machining is useful
inspiration
don’t need to be complicated
e.g. labelmaker, headlines on toilet paper, wire cutter, camera-calibrated hang printer, light-painting in space, scara robot (cool gui interface), StuffMadeHere account
the Toy Story claw, shaper origin by Ilan Moyer, Quentin’s computer vision machine running from python, drawing machine
reference for motion system with kit
everything listed can be built from kit, e.g. belt axis, rotary axis, framing
ilan moyer — https://web.mit.edu/imoyer/www/portfolio/
machines that makes things
foamcore CNC
love letter writer
mighty mill
friendship loom
popfab — portable fabrication
domino tape printer
interactive fabrication
CAD -> CAM -> CNC (from digital to physical rendering and so on) — how to bring the computer into the machine?
realtime control for intent and then computation for transformations on it (e.g. painting)
computation to cad/cam cnc workflow, then changing parameters on the fly (e.g. digital pottery wheel)
last minute advice
sloan student to make the word docs
one person temporarily authoritarian
good organization of subsystems
good interfaces between subsystems
just kind of do stuff and that’s the right attitude
be nice to group members
don’t be afraid of what you don’t know, just find out who knows
can be stressful, lot to do, should be a good time doing it!
don’t take it too seriously, a good project can be super simple
excellent doesn’t have to be monstrous
don’t have to use everything in the kit
feel free to message questions whenever
for the week of, backchannel WhatsApp group — invite people to that if you want help
3. update training section with a refined version of these notes, with link to this slack message https://mit-htmaa.slack.com/archives/C09D5QU46CB/p1762479272595189
1.5x3x7 wax block, speeds and feeds in the video — the part is in fusion team, so you can reference it from there
mostly same as wood, fixturing to machine is different
sizing
stick to wax block, if you need larger discuss with Anthony
registration features
do the math to line them up
materials
for molds
moldstar 15 or moldstar 30 (silicone) — rated for 450F
for casts
hydrostone and drystone (cement-like) — robust can drop, thin does break
metal at a later date, needs face shields and long sleeves
rotomelt-281 melts at 281 F, tin and bismuth, antimony and other traces
epoxies are around, can dye (check bottle brand)
gold in sandcasting for clays or plaster
mold design
aim for no overhangs: two part mold has limited overhangs, can’t mill it in that axis, and even if you print it you can’t remove the silicone with such a small overhang (silicone can tolerate small overhang)
mixing and pouring
requires watertight seal, glue and acrylic, glue and cardboard if missing — fill with water and make sure it doesn’t leak
needs gloves
do the math for size of mold, calculate exactly how much goes in to mix accurately (or just fill with water and measure the volume in a graduated cup)
mix part a and b at 1-1 ratio, mix in the bottle before you pour it out until it feels or looks homogenous
pour more viscous first, then less viscous after, with 50 minutes, mix and scrape, no bubbles, pour in steady stream and only move to where there is liquid
tap when done to get rid of bubbles for up to 1 min
measure the temperature with a laser thermometer to see it heating up
putting under the light speeds up the curing
waxing
hot air on the beeswax with preheater the bottom
paint on a waxing layer, thick and gross and will kill your detail
keep the hot air at relatively low temperature, remelt the wax and get it to settle down into a corner and dump it out, leaving a thin layer on my part covering all the little valleys
putting molds together
clamp them or rubber band them
make the pouring hole big enough to pour into
casting
drystone (20mL water to 100g powder)
put the powder first
then add water
and so on
aim for organic peanut butter-like texture then pour (can add epoxy dye in this step, not good, messes up the curing)
keep the stock with it to know if its cured so you don’t have to dent by poking
4. add a training subsection for molding and casting computer-aided machining, embed this video: https://vimeo.com/1134056661?fl=ip&fe=ec
5. make individual and group assignment sections based on the assignment descriptions: group assignment:
• review the safety data sheets for each of your molding and casting materials,
then make and compare test casts with each of them
• compare mold making processes
individual assignment:
• design a mold around the process you'll be using,
produce it with a smooth surface finish that
does not show the production process toolpath,
and use it to cast parts
• extra credit: use more then two mold parts
6. for the group assignment section, synthesize the answer based on these notes: (for the safety datasheets, find them here https://www.smooth-on.com/tb/files/MOLD_STAR_15_16_30_TB.pdf, https://store-cra054.mybigcommerce.com/content/CertFor202F-281F-281-338FLeadFreeFishingAlloys.pdf , link to meltable alloys https://www.rotometals.com/low-melt-fusible-alloys/?srsltid=AfmBOoqdnepiB0IXePpGMdipwjVxHOb9vuOAuNR9KbWWiivbRjnpySht , https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/sds/usg-hydro-stone-tb-gypsum-cement-sds-en-52000000172.pdf , https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/sds/usg-drystone-casting-media-sds-en-52000000013.pdf and i included pdfs in groupassignments/datasheets when you make the comparison tables put a link to download the pdfs from my repo)
1.5x3x7 wax block, speeds and feeds in the video — the part is in fusion team, so you can reference it from there
mostly same as wood, fixturing to machine is different
sizing
stick to wax block, if you need larger discuss with Anthony
registration features
do the math to line them up
materials
for molds
moldstar 15 or moldstar 30 (silicone) — rated for 450F
for casts
hydrostone and drystone (cement-like) — robust can drop, thin does break
metal at a later date, needs face shields and long sleeves
rotomelt-281 melts at 281 F, tin and bismuth, antimony and other traces
epoxies are around, can dye (check bottle brand)
gold in sandcasting for clays or plaster
mold design
aim for no overhangs: two part mold has limited overhangs, can’t mill it in that axis, and even if you print it you can’t remove the silicone with such a small overhang (silicone can tolerate small overhang)
mixing and pouring
requires watertight seal, glue and acrylic, glue and cardboard if missing — fill with water and make sure it doesn’t leak
needs gloves
do the math for size of mold, calculate exactly how much goes in to mix accurately (or just fill with water and measure the volume in a graduated cup)
mix part a and b at 1-1 ratio, mix in the bottle before you pour it out until it feels or looks homogenous
pour more viscous first, then less viscous after, with 50 minutes, mix and scrape, no bubbles, pour in steady stream and only move to where there is liquid
tap when done to get rid of bubbles for up to 1 min
measure the temperature with a laser thermometer to see it heating up
putting under the light speeds up the curing
waxing
hot air on the beeswax with preheater the bottom
paint on a waxing layer, thick and gross and will kill your detail
keep the hot air at relatively low temperature, remelt the wax and get it to settle down into a corner and dump it out, leaving a thin layer on my part covering all the little valleys
putting molds together
clamp them or rubber band them
make the pouring hole big enough to pour into
casting
drystone (20mL water to 100g powder)
put the powder first
then add water
and so on
aim for organic peanut butter-like texture then pour (can add epoxy dye in this step, not good, messes up the curing)
keep the stock with it to know if its cured so you don’t have to dent by poking
7. for the individual assignment, refine and organize these notes in a wax mold design, CAM, and machining subsections, i will populate the rest in the next prompt
Done based on this tutoral: https://vimeo.com/1134056661?fl=ip&fe=ec
1384.053 mm =54.49 in
Tip to core
172.66 mm =6.798 in
Side to side
50.196 mm =1.976 in
Top to bottom
Full 21.691 mm=0.854 in
Half 10.8455 mm=0.427 in
Alright, in the right size for 1.5x3x7 inches
Scaled later to adjust for wall size clearance of 0.2 inches from timeline (final scale factor was 0.11 for the dimensions to be perfect -- original file is week9/designfiles/kryptonite_arrow_merged.stl)
Glue gun all around with wax on all three fixture points
Switch tool to big tool first and length at 1.5 inches from nut to tip
Tool change and go to MTC, zero x and y
Get Z by putting probe, navigate on top 1-2 inches above. Press auto z touch plate, and click center button after attaching magnet and making sure probe is active
Close the auto z touch plate menu
Check relay 1 and spindle power
Set feed rate to 50% using arrows (typing needs enter)
File -> open g-code
Current tool to 1
Cycle start g-code, and ram up feed rate if sound is okay up to 150%
Remove dust collector, turn off dust relay 1, change tool at 1.5 inches of length to smaller tool
Get Z again the same way
Set current tool to 2
Drop feed rate to 50%, turn on relay 1 for dust collection, Cycle start g-code
Listen ramp up to 100% (in case deep areas, not higher with small tool)
Bring up spindle speed to 115% (to reduce tool chatter)
Remove dust collector
Navigate off wax
Brush off then vacuum
Remove fixtured three points with back of hammer
Score glue with utility knife then slowly move around with putty knife until you can pop off wax
Begin mixing part A and part B, blue into white cup (more viscous into less viscous), comfortably more 120mL (separate cup) + 120mL ended up 220mL (separate cup) and barely filled the mold!
8. make a references subsection in individual assignment and embed all these links for arrow and arrow-related designs (with a brief description of each)
9. add a context/motivation section for individual assignment under references and put this youtube video
https://www.youtube.com/watch?v=OUaDTakFH0U
mention because arrow typically says you have failed this city, this arrow is a symbol for moving forward and when I look at it I say 'I will not fail this class!'
synthesize these notes from chatgpt about kryptonite arrows: (be very brief but don't lose the key points and tagline
🏹 The Kryptonite Arrow
Overview:
The kryptonite arrow is Green Arrow’s signature contingency weapon — a non-lethal countermeasure designed to weaken Kryptonians like Superman or Supergirl if they ever became a threat.
Comic Origins
First appearance: The Dark Knight Returns (1986)
by Frank Miller.
→ A one-armed Oliver Queen fires a kryptonite-tipped arrow to weaken Superman in his legendary duel with Batman.
Later comics, such as Green Arrow Vol. 3 #66 (2006)
, confirm that Oliver keeps at least one kryptonite arrow “just in case.”
Television Adaptations
Smallville (2006-2011):
Season 6 Episode 4 “Arrow”
introduces Oliver using kryptonite arrows against mind-controlled Clark and Zod’s soldiers.
Arrow (CW, 2012-2020):
Season 4 Episode 8 “Legends of Yesterday”
— Cisco Ramon from The Flash gifts Oliver a kryptonite arrowhead as a precaution. It’s kept but never used on allies.
Crisis on Earth-X (2017 Crossover):
In Crisis on Earth-X
, Oliver finally fires the arrow at Overgirl, the evil Nazi version of Supergirl, successfully weakening her.
Symbolism
The kryptonite arrow represents:
Preparedness over blind trust
Human ingenuity versus god-like power
Accountability — even among heroes
Quick Facts
Version Used? Target Reference
The Dark Knight Returns ✅ Superman Link
Mainline Comics ⚡ Sometimes Kryptonians Link
Smallville ✅ Clark / Zod’s soldiers Link
Arrow (CW) ❌ Contingency only Link
Crisis on Earth-X ✅ Overgirl Link
Tagline:
“The kryptonite arrow reminds us that even the strongest heroes need someone who can keep them in check.”
reference this chatgpt link: https://chatgpt.com/share/6910819b-fe58-8008-a4ba-0d7916ed2a58
Human fabrication techniques are inherently more 5-axis than 3-axis—consider using a Dremel to carve a pumpkin. Additional axes are decreasing in cost, making 5-axis machining increasingly accessible. Modern 5-axis machines (e.g., UMC series) now cost around $100k USD, similar to robotic arms with 3–6 degrees of freedom.
3-Axis Machining
3-axis machining removes material through shearing. The load is applied to a bending beam from spindle to tool, where the rake angle determines tool sharpness and cutting efficiency.
Feed (inches per tooth, IPT) and surface speed (SFM) determine the processing window, balancing:
Tool breakage (high feed) — above maximum force
Overheating (high feed/high speed) — above maximum heat load
Buildup/edge formation (low speed) — material adhesion
Workholding options include clamping, vacuum, adhesives, electrostatic, and magnetic methods. Roughing removes material quickly (can take up to 3 hours), limited by moving the part relative to the machine. Parts need to cool, and thermal expansion must be accounted for. The most accurate approach uses the largest tool that fits, not the smallest. Endmill entry is not flat (helical entry into material), and extra stock is used to account for beam bending of the endmill.
Roughing strategies use adaptive/pocket clearing with simulated stepdowns to balance time vs. inconsistencies. Maximum roughing time should be limited to ~30 minutes before moving on. Surfacing creates surface finishes using toolpath options: steep/shallow, scallop, or contour (you can bound the tool to specific areas in Fusion 360). Larger endmills are faster for surfacing operations.
Multi-Axis (5-Axis) Machining
5-axis machining enables reaching and positioning tools, repositioning workpieces for time and accuracy (without manual intervention), and improved surface finishing. The system is always limited by contact at every point in space.
There are two main approaches:
3+2 machining — repositioning then 3-axis cutting
Simultaneous 5-axis — moving more than 3 axes at once, including advanced swarf, multi-axis contour (perpendicular to surface), or multi-axis finishing with ball mills or circle-shaped end mills
Limitations include CAM software processing speed (single-threaded operations), complexity of simulating tool movement relative to workholding and part interference, and managing remaining stock (Fusion 360) or rest material (Mastercam).
Understanding machine kinematics is critical—see the MAS.865 mechanical design resources for detailed analysis of how machines move in space.
Flexibility
With 5-axis capability, the distinction between mills and lathes becomes blurred. Mills hold the workpiece while the tool spins; lathes hold the tool stationary while spinning the workpiece. This flexibility reduces design limitations. Think of systems in terms of three components: the tool, workholding, and axes.
Axes: different spindle configurations, different head designs
Summary
3-axis and 5-axis machining each have their place. The key is understanding which to use when, and how 5-axis capability breaks down barriers between traditional tool classifications, enabling more flexible and creative fabrication approaches.
Useful Documentation
Essential resources for output devices and actuator integration.
Comprehensive resource covering all output device categories including LEDs, displays (LCD, OLED, TFT), motors (DC, stepper, servo, brushless), speakers, solenoids, and more. Includes detailed tutorials, code examples, and implementation guides for various output device types.
Group Assignment: Measuring Power Consumption of Output Devices
Measuring power consumption of motors, servos, and stepper motors using adjustable power supplies and precision energy analyzers to understand performance characteristics and when to use each type.
Measurement Setup
We used an adjustable power supply set to 15V and measured quiescent power consumption of 450 mW (0.03 A, where P=IV) before connecting any motors. Power measurements were conducted using the Joulescope (JS220) Precision Energy Analyzer to measure current, voltage, power, charge, and energy in real-time.
Power supply set to 15V for motor testing
Joulescope JS220 Precision Energy Analyzer
Joulescope software interface
Using a potentiometer to change motor speed, we observed that below a certain threshold, the motor doesn't have enough power to spin (no mechanical work, just electrical losses). Above this threshold, speed increases with power. The dI/dt (rate of current change) cannot change instantly—it takes time. The PWM signal from the microcontroller (roughly 50% duty cycle) is smoothed after passing through the motor driver, with more linear behavior on the rising edge than the falling edge.
Motor circuit connections
Complete motor testing setup
50% duty cycle PWM from microcontroller
Smoothed PWM signal after motor driver
Zoomed-in power measurement
Zoomed-out power measurement
Motor Comparison Results
All motors tested at 15V supply, 2A current limit, with the same potentiometer value for comparison. The potentiometer determines speed and power for DC motors, and position for servos.
DC Motors (Voltage-Controlled)
DC Brushed Motor (Large)
Characteristics: Low-speed, high torque, no positional control
Current: 57 mA
Voltage: 14.49 V
Power: 0.8 W
Large DC brushed motor measurement
DC Brushed Motor (Small)
Characteristics: High speed, medium torque, no positional control
Current: 0.34 A
Voltage: 14.47 V
Power: 4.86 W
Small DC brushed motor measurement and operation
DC Stepper Motor (Current-Controlled)
Characteristics: Medium speed, medium torque, zero absolute positional control (relative positioning only)
Current: 2.0 A
Voltage: 10.93 V
Power: 22.33 W
Stepper motor measurement and operation
Servo Motors (5V Supply, Position-Controlled)
All servos tested at 5V supply, 2A current limit. Potentiometer determines position; power consumption remains relatively constant.
Characteristics: Absolute positional control, slower response, lower power
Current: 5.04 mA
Voltage: 4.99 V
Power: 25.05 mW
Micro servo motor measurement
Motor Comparison Summary Tables
Constant Voltage Comparison (15V Supply, 2A Current Limit)
DC brushed and stepper motors tested at 15V. Potentiometer controls speed for brushed motors, and step rate for stepper motor.
Motor Type
Size
Current
Voltage
Power
Characteristics
DC Brushed
Large
57 mA
14.49 V
0.8 W
Low-speed, high torque, no positional control
DC Brushed
Small
0.34 A
14.47 V
4.86 W
High speed, medium torque, no positional control
Stepper
N/A
2.0 A
10.93 V
22.33 W
Medium speed, medium torque, relative positioning only
Constant Current Comparison (5V Supply, 2A Current Limit)
Servo motors tested at 5V. Potentiometer controls position; power consumption remains relatively constant regardless of position.
Motor Type
Size
Current
Voltage
Power
Characteristics
Servo
Large
10.6 mA
4.99 V
53.4 mW
Absolute positional control, slower response
Servo
Micro
5.04 mA
4.99 V
25.05 mW
Absolute positional control, slower response, lower power
Summary: When to Use Each Motor Type
DC Brushed Motors: Simple applications requiring variable speed and torque, where positional control is not needed
Stepper Motors: Applications requiring precise relative positioning with medium power consumption
Servo Motors: Applications requiring absolute positional control with low power consumption, especially in battery-powered systems
Individual Assignment: Output Devices
Adding simple and complex output devices to the custom development board designed in Week 4, including a bright LED and OLED display for sensor visualization.
Implementing a bright LED output using the MP-3014-1100-50-80 from the Fab Lab inventory. This high-power LED requires careful current limiting to achieve maximum brightness while maintaining safe operating conditions.
Current Limiting Resistor Calculation
For maximum brightness, we calculated the current limiting resistor for a 3.3 V supply driving an LED with a forward voltage (Vf) of 2.85 V. Using a 5 Ω resistor (the smallest available in the shop):
Step-by-Step Calculation
Step 1: Voltage across resistor
VR = Vsupply - Vf = 3.3 V - 2.85 V = 0.45 V
Step 2: LED current
I = VR / R = 0.45 V / 5 Ω = 0.09 A = 90 mA
Step 3: Resistor power dissipation
PR = VR × I = 0.45 V × 0.09 A = 0.0405 W
Step 4: LED power dissipation
PLED = Vf × I = 2.85 V × 0.09 A = 0.2565 W
Result: At 3.3 V with a 5 Ω resistor, the LED draws approximately 90 mA, which is well below the 150 mA maximum rating. This provides slightly reduced brightness compared to maximum, but significantly extends lifespan and reduces heat generation.
Resistor (Ω)
LED Current (mA)
Power in Resistor (W)
Notes
3.0 Ω
150 mA
0.0675 W
Max brightness, close to rated max current (hot)
3.9 Ω
~115–120 mA
~0.055 W
Good balance: bright but less stress
4.5 Ω
~100 mA
~0.045 W
Cooler, longer life
5.0 Ω
~90 mA
~0.0405 W
Selected: even cooler, ~0.26 W in LED, very safe thermally
Bright LED test demonstration
Bright LED circuit on development board
Complex Output Device: OLED Display
Implementing an SSD1306 OLED display for visualizing sensor data. The I²C interface requires two 10 kΩ pull-up resistors—one between 3.3 V and SDA, and one between 3.3 V and SCL. These were soldered onto the connectors of the development board to enable proper I²C communication, which was previously failing in earlier weeks without these pull-up resistors.
Development board with OLED display connected, showing pull-up resistors soldered to I²C connectors
Standard OLED connections: VCC to 3.3 V on ESP32S3, GND to GND, SDA to SDA (pin 5), and SCL to SCL (pin 6).
Accelerometer Data Display
Displaying real-time accelerometer data from the MPU6050 sensor on the OLED screen. This implementation required working SDA and SCL connections with proper pull-up resistors, which were finally fixed this week after troubleshooting I²C communication issues.
Accelerometer data displayed on OLED screen showing acceleration and gyroscope values
Camera Output Display
Displaying camera capture output on the OLED screen with Edge AI inference results. SDA and SCL were not working in previous weeks without the pull-up resistors. While troubleshooting, camera output was verified through the serial monitor, and the input device functionality was confirmed by testing on Quentin's board. With the pull-up resistors now in place, the OLED display successfully shows camera frames and inference results.
Camera output with Edge AI inference displayed on OLED screen showing TTD (time-to-death) prediction
Design Files
Complete design files for sensors display and camera dev board implementations including Arduino firmware and configuration files.
Sensors Display Code
The sensors display script reads data from multiple sensors (MPU6050 accelerometer/gyroscope and HX711 load cell) and displays the values on both the OLED screen and Serial Monitor. The system activates data collection when a button is pressed.
How It Works (Pseudocode):
BEGIN Setup
Initialize Serial communication (115200 baud)
Configure button pin (INPUT_PULLUP) and LED pin (OUTPUT)
Initialize I2C bus (SDA=5, SCL=6) at 100kHz
Initialize OLED display (SSD1306, 128x64, I2C address 0x3C)
Initialize MPU6050 accelerometer/gyroscope (try 0x68, then 0x69)
Initialize HX711 load cell amplifier
Set calibration factor and tare (zero) the scale
Display "Setup complete!" message on OLED
END Setup
BEGIN Loop
Read button state
IF button pressed THEN
Turn LED ON
IF not already collecting THEN
Start data collection mode
Print "=== START DATA COLLECTION ===" to Serial
ENDIF
IF 500ms have passed since last read THEN
Read accelerometer/gyroscope data (acceleration x,y,z, gyro x,y,z, temperature)
Read load cell data (raw value and weight in grams)
Print all sensor values to Serial Monitor
Clear OLED display
Display formatted sensor data on OLED:
- Acceleration X, Y
- Acceleration Z, Temperature
- Gyroscope X, Y
- Weight (grams)
Update OLED display
Update last read timestamp
ENDIF
ELSE
IF was collecting THEN
Stop data collection mode
Print "=== STOP DATA COLLECTION ===" to Serial
Display "Data collection stopped." on OLED
ENDIF
The camera dev board script captures images from the ESP32S3 camera module, processes them through an Edge AI model, and displays both the camera feed and inference results on the OLED screen. The code requires the camera_pins.h header file which defines GPIO pin mappings for the XIAO ESP32S3 Sense camera module.
How It Works (Pseudocode):
BEGIN Setup
Initialize Serial communication (115200 baud)
Configure LED and button pins
Initialize OLED display (SSD1306, 128x64, I2C on pins 5, 6)
Display "OLED Ready!" message
Configure camera module:
- Load camera pin definitions from camera_pins.h
- Set frame size to QQVGA (160x120)
- Set pixel format to grayscale
- Configure frame buffer location (PSRAM)
- Set JPEG quality and frame count
- Configure grab mode (LATEST)
Initialize camera with configuration
Apply vertical flip and horizontal mirror settings
IF camera initialization successful THEN
Set camera_ready flag
Display "Camera Ready - Press Button" on OLED
Set initial capture timestamp
ELSE
Display "Camera init failed" on OLED
ENDIF
END Setup
BEGIN Loop
IF camera not ready THEN
Delay and return
ENDIF
Read button state
IF button pressed (edge triggered) THEN
Set capture trigger flag
ENDIF
Control LED based on button state
IF capture triggered OR 60 seconds elapsed THEN
Reset capture trigger
Update last capture timestamp
Turn LED ON
Display "Capturing..." on OLED
Capture image frame from camera
Turn LED OFF
IF capture successful THEN
Print capture info to Serial (width, height, bytes)
Process and display image on OLED:
- Scale 160x120 image to 128x64 OLED size
- Apply contrast enhancement
- Apply Floyd-Steinberg dithering
- Draw dithered image to OLED
Convert grayscale frame to RGB888 format
Prepare input buffer for Edge AI model
Run Edge Impulse classifier
Get inference result (TTD value in years)
Draw TTD result box overlay on OLED
Print TTD value to Serial Monitor
Return frame buffer to camera driver
ELSE
Print "Capture failed" to Serial
Display "Capture failed" on OLED
ENDIF
ENDIF
Small delay (30ms)
END Loop
Note on camera_pins.h
The camera_pins.h header file defines GPIO pin mappings for various ESP32 camera models. For the XIAO ESP32S3 Sense, it configures pins for the camera data lines (Y2-Y9), control signals (XCLK, PCLK, VSYNC, HREF), and I²C interface (SIOD, SIOC). You need to ensure this file is in a side-tab or included in your Arduino project.
Key insights and learnings from working with output devices and power measurement.
Contributions
Acknowledgements and team roles for output devices work.
Group Assignment
Power measurement of motors, servos, and stepper motors conducted together by the week 8 team with guidance from instructors.
LED Current Limiting Calculation
ChatGPT assisted with the LED current limiting resistor calculation, with correction from Anthony when the initial calculation assumed 5V instead of 3.3V. View ChatGPT conversation
Ethical AI Use
Transparent documentation of AI assistance used in this week's output devices work.
AI-Assisted Week 8 Page Creation and Assignment Documentation
Cursor AI assisted with creating the complete Week 8 documentation page, including the multi-axis machining training section, group assignment power measurement documentation, individual assignment sections for bright LED and OLED display implementations, motor comparison tables, and all formatting and styling. The AI helped refine and organize raw notes into professional, succinct content while preserving key technical details.
ChatGPT assisted with calculating the current limiting resistor for the bright LED. Initially, the AI assumed a 5V supply, but after correcting it to 3.3V with Anthony's guidance, it provided accurate calculations for voltage drop, current, and power dissipation. This helped determine that a 5Ω resistor (the smallest available in the shop) would safely drive the LED at ~90mA, below the 150mA maximum rating.
This week focuses on exploring various output devices and actuators that can be integrated with microcontroller boards. We'll learn about different actuator types, power management, and how to control output devices effectively.
Understanding output device categories and applications
Learning power management and current limiting techniques
Implementing output devices on custom microcontroller boards
This Week's Goals
Explore Output Device Types Learn about LEDs, displays, motors, servos, steppers, speakers, and other actuators
Power Management Understand current limiting, voltage regulation, and power consumption measurement
Implementation Add output devices to microcontroller boards and successfully control them
-
Assignments
Group Assignment Measure the power consumption of an output device
Individual Assignment Add an output device to a microcontroller board you've designed, and program it to do something
Tools & Materials
Microcontroller Boards
Output Devices (LEDs, displays, motors)
Power Supply
Joulescope Energy Analyzer
Multimeter
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Training Documentation
Training materials and documentation for output devices and multi-axis machining.
Multi-Axis Machining
How to multi-axis mill (almost) anything. Understanding the capabilities and limitations of 3-axis and 5-axis machining for complex part fabrication.
Human fabrication techniques are inherently more 5-axis than 3-axis—consider using a Dremel to carve a pumpkin. Additional axes are decreasing in cost, making 5-axis machining increasingly accessible. Modern 5-axis machines (e.g., UMC series) now cost around $100k USD, similar to robotic arms with 3–6 degrees of freedom.
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3-Axis Machining
3-axis machining removes material through shearing. The load is applied to a bending beam from spindle to tool, where the rake angle determines tool sharpness and cutting efficiency.
Feed (inches per tooth, IPT) and surface speed (SFM) determine the processing window, balancing:
Tool breakage (high feed) — above maximum force
Overheating (high feed/high speed) — above maximum heat load
Buildup/edge formation (low speed) — material adhesion
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Workholding options include clamping, vacuum, adhesives, electrostatic, and magnetic methods. Roughing removes material quickly (can take up to 3 hours), limited by moving the part relative to the machine. Parts need to cool, and thermal expansion must be accounted for. The most accurate approach uses the largest tool that fits, not the smallest. Endmill entry is not flat (helical entry into material), and extra stock is used to account for beam bending of the endmill.
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Roughing strategies use adaptive/pocket clearing with simulated stepdowns to balance time vs. inconsistencies. Maximum roughing time should be limited to ~30 minutes before moving on. Surfacing creates surface finishes using toolpath options: steep/shallow, scallop, or contour (you can bound the tool to specific areas in Fusion 360). Larger endmills are faster for surfacing operations.
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Multi-Axis (5-Axis) Machining
5-axis machining enables reaching and positioning tools, repositioning workpieces for time and accuracy (without manual intervention), and improved surface finishing. The system is always limited by contact at every point in space.
There are two main approaches:
3+2 machining — repositioning then 3-axis cutting
Simultaneous 5-axis — moving more than 3 axes at once, including advanced swarf, multi-axis contour (perpendicular to surface), or multi-axis finishing with ball mills or circle-shaped end mills
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Limitations include CAM software processing speed (single-threaded operations), complexity of simulating tool movement relative to workholding and part interference, and managing remaining stock (Fusion 360) or rest material (Mastercam).
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Understanding machine kinematics is critical—see the MAS.865 mechanical design resources for detailed analysis of how machines move in space.
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Flexibility
With 5-axis capability, the distinction between mills and lathes becomes blurred. Mills hold the workpiece while the tool spins; lathes hold the tool stationary while spinning the workpiece. This flexibility reduces design limitations. Think of systems in terms of three components: the tool, workholding, and axes.
Axes: different spindle configurations, different head designs
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Summary
3-axis and 5-axis machining each have their place. The key is understanding which to use when, and how 5-axis capability breaks down barriers between traditional tool classifications, enabling more flexible and creative fabrication approaches.
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Useful Documentation
Essential resources for output devices and actuator integration.
Comprehensive resource covering all output device categories including LEDs, displays (LCD, OLED, TFT), motors (DC, stepper, servo, brushless), speakers, solenoids, and more. Includes detailed tutorials, code examples, and implementation guides for various output device types.
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Group Assignment: Measuring Power Consumption of Output Devices
Measuring power consumption of motors, servos, and stepper motors using adjustable power supplies and precision energy analyzers to understand performance characteristics and when to use each type.
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* End Patch
UserUnknown
in the highlights section add side by side images of drystone and play-doh domes under a title called Ancient Roman Dome (Pantheon model) as the third column in the row (keep first and second as placeholders, first from group assignment, and second will be the arrow)
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone endurance test (left) and Play-Doh form study (right).
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.
Individual Assignment · Kryptonite Arrow Mold
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Wax Mold Design
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.
Green Arrow’s Kryptonite contingency weapon doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.”
Video: Kryptonite arrow highlight reel — reinforces the contingency mindset that keeps Oliver Queen accountable.
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.
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone endurance test (left) and Play-Doh form study (right).
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.
Individual Assignment · Kryptonite Arrow Mold
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Wax Mold Design
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.
Green Arrow’s Kryptonite contingency weapon doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.”
Video: Kryptonite arrow highlight reel — reinforces the contingency mindset that keeps Oliver Queen accountable.
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.
Added a new Week Highlights card ahead of the overview with three columns: group trial placeholder, Kryptonite arrow placeholder, and the Ancient Roman Dome showcase featuring side-by-side Drystone and Play-Doh domes plus caption for quick comparison.
Updated the table of contents to link to the new highlights section for easier navigation.
``32:60:week9.html
Next up: swap the placeholder entries with final images once available and ensure the new dome photos (week9/individualassignment/domes/*.jpg) are in place so the gallery renders correctly.
html
``
UserUnknown
add the images i have in week9/individualassignment/dome for drystone and play-doh domes
Wax machining, silicone molding, and Drystone casting workflow.
Ancient Roman Dome (Pantheon model)
Side-by-side domes: Drystone endurance test (left) and Play-Doh form study (right).
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.
Individual Assignment · Kryptonite Arrow Mold
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Wax Mold Design
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.
Green Arrow’s Kryptonite contingency weapon doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.”
Video: Kryptonite arrow highlight reel — reinforces the contingency mindset that keeps Oliver Queen accountable.
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.
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.
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Wax Mold Design
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.
Green Arrow’s Kryptonite contingency weapon doubles as a personal reminder: “You have failed this city” becomes “I will not fail this class.”
Video: Kryptonite arrow highlight reel — reinforces the contingency mindset that keeps Oliver Queen accountable.
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.
Added an SDS-driven safety callout under Group Assignment summarizing PPE, ventilation, first aid, and disposal guidance for Mold Star silicones, USG Hydro-Stone, USG Drystone, and RotoMetals Roto281 alloy, with citations back to the reviewed datasheets.
Highlighted key risks: amine sensitizers in Mold Star, gypsum dust/alkaline exposure in Hydro-Stone and Drystone, and molten-metal hazards with Roto281—plus explicit first-aid and storage reminders.
``212:245:week9.html
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.
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.
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.
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
Wax Mold Design
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.
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: Kryptonite arrow highlight reel — open in a new tab if embedding fails.
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.
Replaced the embedded player with a clickable thumbnail that opens the Kryptonite arrow video directly on YouTube in a new tab. The figure now uses the official thumbnail as a preview, includes a clear “Open on YouTube” button overlay, and updates the caption to mention opening in a separate tab for reliable playback.
UserUnknown
make Kryptonite Arrow Mold a subsection under Individual Assignment, make Arrow & Inspiration References and Context and Motivation subsubsections in this, the part already there should be called Kryptonite Arrow Molding
AssistantUnknown
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Individual Assignment · Kryptonite Arrow Mold
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
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Wax Mold Design
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Individual Assignment
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This week’s personal focus: design, machine, and cast a Kryptonite arrow replica that demonstrates clean mold surfaces and reliable registration.
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Kryptonite Arrow Mold
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Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
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Kryptonite Arrow Molding
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Fusion 360 CAM Strategy
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Machining Workflow
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Silicone & Casting Plan
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Arrow & Inspiration References
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Arrow & Inspiration References
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Context & Motivation
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!
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Context & Motivation
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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!
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Video: Kryptonite arrow highlight reel — open in a new tab if embedding fails.
+ Video: Kryptonite arrow highlight reel — open in a new tab if embedding fails.
* Begin Patch
* Update File: /Users/saleem/MIT/classes/htmaa_25/week9.html
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Individual Assignment · Kryptonite Arrow Mold
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
-
Wax Mold Design
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.
-
Arrow & Inspiration References
+
+
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.
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.
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!
Open on YouTube
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.
* Begin Patch
* Update File: /Users/saleem/MIT/classes/htmaa_25/week9.html
@@
Individual Assignment · Kryptonite Arrow Mold
Documenting the wax machining, silicone molding, and Drystone casting plan for the week9/designfiles/kryptonite_arrow_merged.stl model.
-
Wax Mold Design
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.
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!
Open on YouTube
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.
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.
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.
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.
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.
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.
Reworked #individualassignment into a parent section with nested content: #kryptonite-arrow-mold now houses all mold/CAM/workflow/casting notes under a new “Kryptonite Arrow Molding” subheading.
Folded #references and #motivation into sub-subsections within that card so the arrow resources and narrative context stay grouped with the mold documentation.
Added consistent styling tweaks (shared background blocks, ASCII quotes, adjusted copy) while keeping existing anchor IDs so table-of-contents links continue to work.
UserUnknown
add arrow-mold.gif from individualassignment/arrow to the highlights placeholder, make it link to individual assignment section
Hydro-Stone, Drystone, and alloy comparisons (full documentation below).
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.
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.
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.
Replaced the week highlights arrow placeholder with the real GIF:
The second highlight column now links to #individualassignment.
It displays week9/individualassignment/arrow/arrow-mold.gif with an informative alt tag.
Caption remains the same so the animation’s intent stays clear.
UserUnknown
add groupassignment-moldingcasting.jpeg side by side with groupassignment-lion from groupassignment/images to the highlight placeholder and make it link to group assignment, add a contributions section to the page thanking Anthony for training and lion demo, James and 1.583 course staff Prof. Josephine Carstensen and TAs Hajin and Dat for help with Dome design, and thanking Omar for his help with designing the mold in two parts and then anthony for his help with converting to three part mold (link omar's molding and casting website for his cool shuriken! https://fab.cba.mit.edu/classes/863.20/Architecture/people/OmarAlDajani/Week4.html
add ethical AI use section and put the chatgpt lore link first
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For the complete technical details and full conversation transcript:
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