Week 9 - Molding & Casting Group Assignment

Mold Materials

Casting Materials

Process Takeaways

• Machine wax blanks with >=5 mm wall thickness and add alignment bosses to minimize silicone flash.
• Proof mold boxes with water, then pour silicone in a thin stream and tap for about 60 seconds to release bubbles.
• Keep oversized pour spouts and witness buttons so we can monitor cure without disturbing the part.
• Match casting medium to duty cycle: Hydro-Stone for strength, Drystone for fidelity, and Roto281 for reusable metal prototypes.

Best Practices for Mold-Making Processes

• Prep wax with three-point hot glue fixturing and maintain thin beeswax skins for easy cleanup.
• Size registration bosses intentionally so silicone halves seat without flash or misalignment.
• Mix silicones by pouring the heavier component first, scrape walls, and pour in a steady ribbon.
• Use oversized sprues, vents, and clamp pressure that suits each casting medium.

Comparing Mold-Making Processes

• 3D-printed tooling: fast turnaround for complex shapes, but needs sealing to hide layer lines.
• CNC-machined wax: best surface finish and registration, trades for longer CAM prep.
• Hand-sculpted wax: quick for simple forms, limited to low-temperature casting media.

Negative vs. Positive Mold Workflows

• Direct negative molds: cast straight into rigid tooling—great when parts have easy draft and tolerate demolding forces.
• Positive-to-negative sequences: machine or print a master, then pour silicone inserts for flexible release and repeatability.
• Choose flexible tooling whenever undercuts, delicate surfaces, or repeated pours are expected.