For our final project, the ENGI 210 class was tasked to make a black and white chess piece. I chose to make the King of the chess set.

The method by which we created our chess piece was very inefficient. The first step was to CNC mill two positive images of the chess piece, create a cast of both images, and finally combine and fill our casts to create the final piece from plastic.

Originally, we planned to use a piece from Thingiverse. However, we were never able to properly import and edit the STL files from Thingiverse. To work around this, we chose a piece from GrabCad. GrabCad files come in SLDPRT files. This was crucial to our project, because these new files allowed us to manipulate and edit our desired chess piece.

Once we selected our chess king, we had to prepare it for CNC Milling. First, we imported the full piece into Solidworks and split the model into symmetric halves. Next, we imported one symmetric half in Fusion 360. We also created key holes in this step that we hoped would help us line up our molds. In Fusion 360, we were able to set our stock piece and create a G-code toolpath for CNC Milling. This was by far the hardest step in the project. My partner and I struggled to create a G-code file that was compatible with the Flashcut CNC Machine. After consulting the blog posts of previous ENGI 210 students and other current students in the class, we learned that we needed to download a machine configuration file from Easel to create our G-code. However, this only fixed some of our problems. We were finally able to create a compatible G-code file after getting help from another ENGI 210 student. We ended up copying the machine settings from his Fusion 360 file. In doing this, we discovered that we had misconfigured some settings in the feed optimization window and tool coolant. After this step, we finally exported a compatible G-code file.

 

Once we had a working G-Code file, we went to work on the CNC machine. This step ended up being just as difficult. Each half took about two hours to fully machine. On our first cut on the CNC machine, we accidentally used a stock piece that was a little too small. This resulted in part of our king not being cut into our stock piece. We stopped the cut and started over once we had a properly sized stock piece. Then our second cut failed for unknown reasons. After cutting about half our king, the machine stopped cutting and started tracing its tool path far above our stock piece. We think that the machine might have been accidentally reset during the cut.

Persevering on, we started our third cut. This time we got it mostly right. Our king was accurately cut into our stock piece, but some of our alignment keyholes were cut off from the side of the stock piece. Instead of starting over again, decided that the best use of our time was to move forward with our fourth cut. This cut achieved identical results to that of our third cut.

Once we finally had our positive images, we created our molds. First, we created casings around our CNC cuts out of lego. We also hot glued our pieces to the bottom of our casings to keep them in place during casting and wrapped our casings in duck tape to prevent any leaks.

 

Then, we used Smooth-On Mold Star to create the molds. This product was easy to use and took 4 hours to set. We decided to do both molds of our piece in order to save time.

Now, we were on the final step. All we had to do was combine our molds and cast our final piece. Since our mounting keyholes failed, we were forced to manually align our molds. This was not only difficult but also created slightly deformed pieces requiring significant post-processing. For both king pieces, we used Smooth-Cast-385. This product was easy to work with and set in only 15 minutes.

For white king piece, we dyed our Smooth-Cast-385 white and poured it into our molds. This piece came out the nicest of all our casts and required the least amount of post processing despite being our first try. Despite our great casting, we did not use enough dye and were forced to paint our piece white.

For the black king piece, we ran into problems. Despite our best efforts, we were unable to align our molds as well as we did for the white chess piece. We were forced to cast this piece twice. After our second cast, we decided to go ahead and post process our best cast.

To post process both of our pieces, we lightly sanded the pieces with a dremel and spray painted the pieces.

This project was very difficult and frustrating. I found the CNC Milling in particular to not be very enjoyable.