For the final project, my teammate and I created a chess piece, specifically the Bishop. This was done by machining a positive mold out of wood with the CNC, using this to create the negative mold, and then creating the actual bishop piece from this mold.

We began our project by finding a .sdl file of a bishop on Thingiverse. This file was then cut in half down the tall axis using Solidworks. After converting the file to different formats a few times, we managed to get it into Fusion 360, where we added the block to the file on top of which the bishop half would rest.

In Fusion 360, we added circular keys so that it would be easier to align the molds later on. In order to convert this file into the proper gcode format, we simplified the file by minimizing the number of faces. Finally, we removed the ‘G54’ line of code from the gcode file thanks to a tip from previous ENGI 210 students. With this completed, the conversion proceeded smoothly.

The CNC machine step of our process while not difficult, did present us with numerous learning situations. The first of these occurred when while cutting, we realized that our file’s block size was too small, and walls were being left behind. Thus, when the drill bit began its second layer, it ran into the wall and broke. To fix this, we simply edited our code in Fusion 360 and tried again. We also learned a lot from playing around with the code and various settings.

This allowed us to center our block about the correct origin for cutting, and finally the blocks were cut successfully.

Our next step was making the mold. This was done by making Lego boxes to surround our CNC prints on 5 sides, and filling them with Smooth-On silicone rubber. Anti-adhesive spray was used on the blocks to keep the mold from sticking, and after the Smooth-On parts A and B were mixed, they were poured into the boxes and left to cure for 24 hours. The molds turned out well, and they required only minimal post processing such as getting rid of excess Smooth-On.

 

 

 

 

 

 

 

Once the molds were finished we proceeded to the final step: making the piece. For the final part, we used another Smooth-On product- Smooth-On 385, which worked similarly to the mold material but it was a firm plastic rather than a flexible rubber. To make the part, we measured the correct amount of material, mixed parts A and B together, added dye if any, and then poured the mixture into the mold through a funnel made out of construction paper.

The first piece was neither correctly aligned nor dyed. The second piece was dyed, but not correctly aligned. With the third piece we figured out the method for aligning the molds properly  in order to minimize the seam. Basically, we had to look down the molds and line them up gradually as we closed the mold, wrapping it with rubber bands each step of the way. Through this process we were able to attain two bishops, one white and one black.

 

Our post-processing consisted of mostly sanding and using the dremel. The black piece had actually been dyed with a combination of purple and brown dye (we had run out of black) but the coloring was off, so that piece was spray painted as well.

To summarize, this project taught us about the casting and molding process. While other techniques such as milling or 3d printing might have been more realistic, this process taught us about the method to use if we wanted to create a part multiple times in a time and cost effective way.