As a team, we weren’t able to work together as much as on our previous midterm project due to poorly aligned schedules. That said, our work together on the midterm project helped our communication, and we were able to successfully complete this project by splitting up parts of the project to create a final product that we are proud of!
We started by looking for interesting chess files on Thingyverse, and we found a cool Egyptian-themed chess set. We still don’t know exactly what the piece that we decided on is in an actual chess set, but we decided on the piece that we did because it was complex enough to present a challenge, but not so intricate that it would not be able to be molded.
We got the piece approved by the teaching team, and we cut it down the middle in MeshMixer in order to get two symmetrical halves. After cutting the piece in half, we used one half to create a mold in Solidworks and OnShape, which included pins and holes to allow for secure connection of the two halves of the mold:
In our final model, we also added a second “box” piece to contain the chess piece mold as it was poured. The box piece also had considerable space on the sides of the piece to ensure that the mold would produce the desired chess piece intricacy once poured:
As shown above, the outer mold container was done in the less expensive PLA filament using an FDM printer since detail was not necessary. The actual piece was done using SLA printing with resin to get more detail in our final piece.
We then poured the mold using a 1:1 volume mixture of the molding solutions. The final product came out well, and allowed for a hole for pouring at the bottom of the mold. Because the two pieces were mirror images of each other, the molds fit nicely together and created the full shape once the pins were joined.
With the two mold halves created, we were ready to pour the eight chess pieces! We rubber banded the two halves together to ensure that the pins stayed together and didn’t shift since they were rather soft and malleable.
We poured the molds in a 1:1 volume ratio of the two liquid plastic mixture parts. After some trial and error, we found that the optimal volume was about 20-25 mL of both parts to allow for filling the mold without too much excess. After waiting for about 10 minutes, the piece would set. We then took out the piece and repeated the process to get all eight pieces.
Due to issues with how tightly our mold stayed together, the unfinished version of our pieces had excess plastic down the middle. Another imperfection with our pieces was inconsistencies with pouring the top of the mold, which translated to the bottom of the piece. This made the bottoms not flat, so some of the pieces couldn’t balance on their own out of the mold. Fortunately, both of these issues were easily fixed with post-processing: the middle ridge was removed using an exacto knife and sanding, while the bottoms were made smooth using sanding and filing.
After this post-processing was carried out on each piece, we had our final chess set!
It is also worth noting that although we didn’t physically CNC half of our mold out of wood, we did use the 3D file that we created in Solidworks to make a CNC file in Fusion 360 that could be executed if desired This process consisted of a variety of software steps, including transforming the file’s representation in Fusion 360, placing the model in the appropriately-sized wood block, and customizing the resulting toolpath:
Cost Analysis
The project took about eight hours total between the two of us. Assuming a pay rate of $15/hour, this translates to $120 total in labor costs. The PLA and resin combined for the 3D prints used to make the mold cost a total of only about $4 [1,2]. The mold silicone package costs $52, but we only used a small part of it, so this cost can be approximated to be $4.00 (using 1/13 of the bottle) [3]. We used slightly more of the liquid plastic used to cast the final chess pieces. The full kit costs about $150, and we can assume that we used about 1/10 of it, or $15 worth [4].
Overall, then, the total costs comes out to be about $143 for the chess set, most of which is again caught up in the labor time. Because there were not any machines used other than the 3D printers (which are open access), no machine use costs were incorporated.
References
- Arceo F. Resin vs filament cost in 3D printing! [Internet]. 3Dsolved.com. [cited 2022 Apr 16]. Available from: https://3dsolved.com/resin-vs-filament-cost-in-3d-printing/
- FDM vs. SLA: Compare filament and resin 3D printers [Internet]. Formlabs. [cited 2022 Apr 16]. Available from: https://formlabs.com/blog/fdm-vs-sla-compare-types-of-3d-printers/
- PlatSil 73-25 – all kit sizes [Internet]. brickintheyard. [cited 2022 Apr 23]. Available from: https://www.brickintheyard.com/collections/tinsil-platsil-silicones/products/7325u16
- EasyFlo 60 Liquid Plastic [Internet]. Polytek Development Corp. [cited 2022 Apr 23]. Available from: https://polytek.com/products/easyflo-60-liquid-plastic
