Final Project | ENGI 210: Prototyping and Fabrication

By Gabriel Witkop and Surina Kishinchandani

For our final project, we molded and casted 4 chess pieces. We chose this for our chess piece: https://www.thingiverse.com/thing:5029303. It’s the shape of a generic person.

First, we modified the shapefile so that it can be both 3D printed and CNC machined. After doing some modifications to the existing base mold files to perfectly size them to the model and avoid wasting silicone, we 3D printed one half of our chess piece out of PLA. We then used this 3D-printed half to make the silicon mold. In order to make the mold, we cut out pieces of cardboard to form a box of indeterminate size and hot glued it to the 3D printed piece we had. Once we were sure that no leaks would form, we poured in our silicon mixture.

Next, we completed CAD planning in preparation to CNC machine the one-half positive of the chess piece. We used VCarve to prepare the file and carved out our piece on the Nomad3 CNC machine. For this part of the project, we used a roughing pass using a ⅛ in flat endmill. After we did that, we completed the other half of the mold by making another box of indeterminate size around the CNC half, hot gluing it and then pouring in a silicon mixture.

Finally, using molding and casting processes, we made two half negative molds and then repeatedly cast resulting chess pieces from that mold. We secured both parts of our silicon halves with rubber bands to prevent leaks. Although we had a couple of discrepancies with alignment, we ended up with 4 nearly identical chess pieces. For our first piece we used the slow-curing polyurethane, which took 30 minutes. We didn’t want to wait so for the remaining 3 chess pieces we used the polyurethane with a 3-minute cure time. We decided to dye our last piece pink.