Casting

I first opened up all of the design files that I had to determine the inches cubed of material I would need to cast all of my designs. I then converted cubic inches to milliliters, determining that I needed about 150mL of material.

Before filling my molds, I sprayed mold release onto the molds. This ensures that after the cast solidifies, the mold and cast separate easily.

For my casting, I used Smooth-On Mold Star 15 Slow, which came with a Part A container and a Part B container. To produce 150mL of Mold Star, I mixed 75mL of Part A with 75mL of Part B.

I then poured the Mold Star onto each of my molds.

After the Mold Star solidified, I took them out from the molds.

Here is the cast of the parakeet from the Prusa mold.

Because the wax I used for milling had imperfections, the heart cast had some bubbles along the edges.

I used an exacto-knife to manually cut away the bubbles. Here is what the final heart mold looks like.

My first cast on the resin mold didn't end up working because I mixed the Part A and Part B solutions improperly. The cast ended up having bubbles in it and wasn't very solidified, even after settling overnight.

I then re-cast the resin mold with a properly mixed solution. Here is the final parakeet from the resin mold.

Draft Angles

Although I didn't think of doing this during my molding week projects, my global evaluator, Iván Milara, told me about using draft angles, or creating walls at specific angles, to help the casting process. Specifically, using draft angles allows for using different kind of milling bits, along with providing a host of benefits during the de-molding process, including minimizing stuck walls and reducing warps/scratches/tears. The optimal draft angle depends on several factors including the material of the cast part, the complexity of the design, and the type of molding process used. However, a general guideline is to have a draft angle between 1° to 3° for most materials and processes.