14. Moulding and Casting¶
Overview¶
This week’s goal was to create a mold without any visible production marks and use it to cast parts. I chose a 3D-printed gear I designed as the model for my mold. I worked with my group mate, Tyler Russel, who had also designed a gear with a slightly different geometry. I opted to create a soft mold using a silicone rubber mixture (Part A and Part B) so that I could produce multiple hard resin casts—potentially useful for future mechanical or design projects.
Gear¶
I made a gear in fusion 360 for this week. I made it by extruding a sketch with one tooth:
The I used the circular pattern tool to create more teeth, the combine tool to combine the bodies, and filet to round things out.
Molding Process¶
To make the mold, I used Mold Star Series Platinum Silicone Rubber, which requires a 1:1 mix ratio between Part A and Part B.
Part A
Part B
After removing the lids from both containers, we stirred each part thoroughly. We then poured equal volumes of Part A and Part B into separate red plastic cups.
Once measured, we poured the contents of both cups into a clean popcorn bucket at the same time to ensure uniform mixing.
Before pouring the silicone mixture, I hot glued my 3D-printed gear into the base of the bucket to hold it in place. I ensured the mixture covered the gear completely to capture all details in the mold.
After allowing it to cure for 12 hours, this was the final mold:
Casting Process¶
For casting, I used TotalBoat TableTop Epoxy, a clear hard resin that cures into a durable part.
I started by measuring 100 mL of Part A and 100 mL of Part B in two separate plastic cups. I then combined both into a single cup. With Tyler’s help, we stirred the mixture until it transitioned from cloudy to clear—indicating thorough mixing.
We then carefully poured the epoxy resin into the silicone rubber molds.
To eliminate trapped air bubbles, we used a heat gun over the surface of the resin immediately after pouring.
We allowed the cast to cure for approximately 3 days. Once fully solidified, we gently removed the final cast pieces from the molds.
Reflection¶
This week felt like a breath of fresh air, especially after machine week. One key takeaway was the importance of accuracy when measuring and mixing materials—especially for consistent mold quality and strong resin cures. It was helpful to work with a partner like Tyler, who provided a similar model, allowing us to compare results and share techniques. Using the heat gun was especially effective in reducing air bubbles and it significantly improved the finish of our cast pieces. Overall, the process was smooth, and I’m proud of how reusable and nice the molds turned out. I’m excited to explore ways to use these techniques in future design and engineering applications.