Creation of master positives for chess piece molding

For this project we had to create two master positives to take negatives of. one had to be 3d printed and the other had to be CNC routed. To start we downloaded an stl model of a chess piece from thingiverse. we then imported this piece into autodesk inventor and used it as a reference to recreate the piece. This was done primarily to increase the surface curvature accuracy because the stl from thingiverse didn’t have than many polygons. We then cut the piece in half and added a back plane. For the 3d printed side the piece and back plane was done on the form 2 for the good surface detail, and the mold additions like an air hole and alignment ridge were done with the maker gear because it didn’t need high detail. the two parts were then glued together.

to make the CNC side, a similar process was repeated, except the mold additions were integrated with the base plane and piece model. instead of the alignment ridge protruding, it was inset. we did make a slight mistake with air hole. Instead of doing it such that they lined up when both half put together, they were on opposite sides. ultimately this doesn’t really matter since it just means that there are tow paths for the air to escape. once a model was generated, it was imported into fusion 360. Using fusion 360’s CAM environment, the file was prepared and g-code was generated for a roughing pass using a 1/8 bit, and a crosshatched detail pass using a 1/16 bit. Once the g-code was generated it was uploaded to easel. It took a couple of tries to generate g-code that avoided the smart clamp because the piece of wood we were using barely fit. We then clamped the piece of wood into the carvey, installed the correct bit, and then hit run. After it finished, we swapped bits and ran the second pass. The process removed a few chips of wood from thin areas, but these areas would show up as bits of extra material that can be removed from the negative.

To see how the negetives were made an used, check out my partners blog post:

http://engi210.blogs.rice.edu/2019/04/29/its-pouring-plastic-men/

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