Hi everyone,
For our BIOE555 final project, our goal was to create four molded Duck Chess pieces. We are excited to share our results!
The Process
We began our project by exploring different Duck designs on Thingiverse. After reviewing several options, we identified a design that was both appealing and practical for our project. However, the base of the chess piece had a complex shape that could pose challenges during the molding process. To ensure a smoother workflow, we made some modifications to the base design, simplifying it and improving its overall feasibility for CNC machining.
PICTURE
Once we had made the adjustments, we created a 3D printed prototype of our modified Duck design. This prototype allowed us to assess the changes and verify that the piece would function well for both the molding and CNC machining steps.
Design Modifications and Slicing
At this point, we needed to slice the Duck into two halves for the mold. Additionally, we decided to add a base to the design in SolidWorks. The addition of the base was crucial for the molding process, as it would help to anchor the piece in place and provide a sturdy foundation for the final cast.
Creating the Mold
After finalizing the design and completing the 3D print, we moved on to the next stage: creating the mold. To do this, we first hot-glued cardboard around the 3D printed Duck piece, ensuring that the piece was securely attached. This cardboard frame would serve as a barrier for the silicone mold.
Next, we carefully mixed the silicone solution (Part A and Part B) and poured it into the cardboard frame, fully covering the 3D printed piece. We allowed the mixture to cure for 24 hours, ensuring that the mold was set and ready to use. Once the silicone had cured, we carefully removed the mold from the cardboard, revealing a detailed and accurate replica of the Duck piece. 
CNC Process
The next step in the process involved using the CNC machine. With the mold now in hand, we were ready to proceed with the final stages of the project. The CNC process allowed us to create the precise, high-quality parts we needed to complete our Duck Chess pieces. The whole p;iece took approximately 2 hours and a half to complete, and we used two different tools. The first tool, an end mill (1/4 inches), was used to speed up the process of carving the bigger areas of our design, while the second one, a ball nose (1/16 inches), was used for the finer details. We used an rpm of approximately 1900. Our stock wood piece had the following dimensions:
- Width: 6 inches
- Height: 3.5 inches
- Depth: 1.5 inches
The most difficult part of this process was the adjustment of the holds of the CNC machine, as they were not suitable to use with such a thick stock piece. Having said so, we had to create a “pocket”-like structure on each side of the wood block to insert the green holders to secure the piece to the working CNC table, as shown below.
After having our piece ready, we clear coated it with the mold release coat spray to prevent the silicone from attaching too much to our wood mold. The following day, we came back to the OEDK and poured the silicone using the same technique used for the 3D printed part. After leaving it to cure for approximately a day, we took it out of the wood CNC machined piece and we had the other half of our duck ready to go.
Polyurethane Casting
After acquiring the negative molds from the positive CNC chess piece half and the 3D printed chess piece half. We fit the two negative molds together and secured their structure with rubber bands. We then began to mix our polyurethane casting resins to pour into our mold. After pouring, we would wait around 10 minutes for our chess pieces to cure. Using colored dye, we were able to customize the colors of our 4 chess pieces, making green, brown, pink, and white colored chess pieces.
Finally, at the end of every session we made sure our space was properly cleaned, as shown below.
Cost Analysis
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | White PLA roll | $19.99 | https://us.store.bambulab.com/ | 1 | $19.99 |
| Lumber for wood blocks | $1.52 | https://www.homedepot.com/ | 1 | $1.53 | |
| Smooth-on casting resin kit A&B (pint unit) | $26.61 | https://www.amazon.com/ | 1 | $26.61 | |
| Molding Silicone TC-5130 kit A&B (gallon unit) | $206.40 | https://bjbmaterials.com/ | 1 | $206.40 | |
| Hot Glue Gun | $2.25 | https://www.joann.com/ | 1 | $2.25 | |
| Hot Glue Sticks 24pk | $5.99 | https://www.joann.com/ | 1 | $5.99 | |
| Cardboard | $1.63 | https://www.uhaul.com/ | 1 | $1.63 | |
| Exacto Knife | $2.79 | https://www.hobbylobby.com/ | 1 | $2.79 | |
| Plastic Container 25pk | $25.00 | https://www.uline.com/ | 1 | $25.00 | |
| Popsicle sticks 50pk | $0.97 | https://www.walmart.com/ | 1 | $0.97 | |
| Labor | Prototyping Engineer (You!) | $36.48/hr | https://www.ziprecruiter.com/ | 8 | $291.84 |
| Overhead | Facility Cost (Machine Time) | $50/month | https://apps.txrxlabs.org/join-us/ | 1 | $50.00 |
| Design | Engineering and Development | $60.70/hr | https://www.talent.com/ | 4 | $242.80 |
Total Cost: $877.80
Overall, this project costs a total of $877.80 including both labor and materials.
