For our final project, we created a cone-shaped cat (https://www.thingiverse.com/thing:4704681) because we thought it was cute and a relatively straightforward shape that still had some complexity with the tail wrapped around it. Before choosing this design, we had wanted to create a bunny, but we ran into trouble with the shape of the bunny, especially with the ears. Thus, after consulting the TAs, we switched to this design, which was much better.
To start this project, we test-printed a 3D-printed cat with 40mm x 41.14mm x 75.15mm dimensions. We were satisfied with the size and brought that file into Meshmixer and SolidWorks to turn into mold bases. We had some trouble with this step at first, seeing that it was the first time either of us had used this software before; however, after a while, we got the hang of it and successfully created files for the positives of both sides of the cat mold.
We decided to make the front of the cat the one we 3D printed, due to how small the face details were. It printed very smoothly, and we were delighted with the result.
During class, we made a box of indeterminate size using cardboard and hot glue to put around our 3D print to hold in the silicone after we poured it onto our mold positive. We then mixed and poured the silicone into the box we made and left it to set.
We moved on to CNC carving the mold positive of the back of the cat. This step also gave us a lot of trouble, seeing that neither of us had ever used VCarve. After many clicks through different commands and functions in the VCarve program, we finally successfully created a file to CNC that had both a roughing path for the initial carve and a detailing path to smooth it out. At first the program was giving us a cut time of five hours for just the roughing path alone, which we figured was too long, so we consulted with a lab assistant who helped it change the rotational settings of the bit to a high level, eventually cutting the cut time down to under an hour. We did the same for the detailing path and eventually got the whole carve sequence under two hours. We clamped down the wood and started the CNC cut. Thankfully, everything went very smoothly, and we got a nicely carved mold base of the back of the cat in one go, which we were very excited about!
After we made the CNC mold positive for the back of the cat, we once again created a box of indeterminate size, mixed silicone, and poured it to create the mold negative of the back of the cat. We let that sit until it also cured, then moved on to the last step of our process.
We took the two mold negatives and bound them together with rubber bands, and then mixed polyurethane. We calculated that we needed around an ounce of Part A and Part B volumetrically. After we mixed Parts A and B and the dye, we quickly poured them into the mold, remembering that the pot’s life was very short. We then waited for 10 minutes before demolding the cat chess pieces. We used sandpaper to sand down the seam where the two halves met.. At first, we had trouble aligning the front and back of our chess pieces, even with the notches in the mold negatives. We figured we were being too aggressive when turning the mold to make sure the polyurethane got into all the nooks and crannies, and it shifted the mold pieces. So after that, we made sure to be more gentle, and it did help us align our halves better!
In general, this project was quite the learning experience! There were quite a few times when we got stuck trying to figure out new software, but the process became much smoother once we got the hang of the software. We got a lot better using the CNC machine, which we appreciate in hindsight. The chess pieces we created were adorable, and we are satisfied with how the colors turned out!
Here is a picture of our cleaned workspace:
Cost analysis:
Full 3d Bambu Print + Half Banbu Print (45.43g) = $2.72
Wood for CNC (2 x 6 x 3.5 in) = 3.55
600 ml of Silicone = 10.91
10 oz of polyurethane = 8.67
1 pack of rubber bands = 1.68
Labor Cost: 40 hrs ($10/hr)
Total Cost: 427.53
