Hi everyone!
Cris and I worked together to create our Rocket chess piece. Overall, this project was low stress with incredible outcomes.
Designing 3D Part
Figure 1: 3D Printed Part
Initially we were unsure of what piece would be the easiest to mold and decided to have three options from thingiverse.com. After a few days of thinking about it, we found one file with rockets. We uploaded it to MeshMixer and decided to add a small window to the face of the rocket to make it more playful. Once the part was split in half, we reduced the number of triangles to less than 10,000 and imported the file to SolidWorks to add additional functional features. We scaled the size and added 4 pegs to the outer face of the chess piece. We repeated this process for the second part, but the pegs were inverted and slightly smaller. Once this was completed, we sent the part to print and had a good looking rocket in 4 hours.
CNC File
Using one of the .stl files made from SolidWorks, we imported the file to Fusion360. We followed the instructions given during class and chose 1/8″ flat downcut drill bit for the initial cut and 1/32″ flat downcut drill bit for the smooth cut. We did run into a problem initially because Fusion had scaled our rocket x10 which made the program crash multiple times. In hindsight we should have double checked the dimensions before struggling with the software. But once the tool path was created, it was easy to make a g-code using Easel.
Molding
Figure 2: Cardboard Encasement
Once we had our 3D parts, we decided to create the silicone mold. As the mixture is 1:1 by volume, we used a total of 200mL and evenly split it between both molds. Before mixing everything, we used cardboard to create a barrier for the mold and used a lot of hot glue. Unfortunately, it was not sealed perfectly and we had some leakage once we poured in the silicone. We panicked and added a lot more glue, but eventually we decided to add another piece of cardboard at the bottom and glue both the molds onto that piece. After leaving the mold to cure for the night, we de-molded using box cutters against the cardboard. It was slightly difficult because of the amount of glue we used, but we were very surprised and happy with the mold quality once it was released from the 3D printed part.
Casting
Figure 4: Mold with Liquid Plastic
Figure 3: First Cast
This next process was definitely going to be the deciding factor for the success of everything we did before this. Luckily we caught Douglass and Dr. Wettergreen for our first cast and they guided us through the process. Before mixing, we first aligned the pegs and tied the molds with rubber bands to avoid spillage and ensure the two halves were aligned. We used 7.5 mL of each part as it is 1:1 by volume, mixed it very quickly, and slowly poured it into the opening at the bottom. After waiting for 20 minutes, once the mixture started going white, we de-molded the piece and were super happy about the success on our first try. We could clearly see the 3D printed lines and there was an air bubble on the ring at the tip of our rocket, but it was still a successful piece. Following this, we casted 7 more pieces with a cure time of 12 minutes (measured by a timer).
Figure 6: Green part
Figure 5: Green explosion
We had a fun little science experiment as well! Since there were no good colors to use, we had to go with all white chess pieces. But towards the end of this casting process, we were given a green color to try out. That turned out to be a cool experiment as there was an explosion and a lot of overflow with bubbles. The last piece that we casted has a bit of green on the sides because of the leftover colors from the previous experiment. We really like the look of it so we decided to keep it.
Our pieces were relatively aligned all the way, so we only needed to sand down the bottom part to make them all even.
Cost
Silicone mold (~$300/2 gallons): 200 ml = $7.92
Liquid plastic (~$145/2 gallons): 120 ml = $2.30
3D printed part = $0.72
Labor ($15/hr): 5 hrs = $75
Negligible costs as it is provided by the OEDK: cardboard scraps, rubber bands, mixing cups, hot glue, softwares (SolidWorks and Fusion 360), 3D printer
Total Cost: $85.94
This was a really great final project because we were able to work with so many different mediums and even though we did not CNC the other half, it was good to learn how to set up a g-code file through Fusion360.
