Crafting Our Beginner-Level Chess Piece: A Journey Through Prototyping and Fabrication

For our final project in EDES 210, we set out to create a custom chess piece using CNC machining, molding, and casting techniques. This process involved overcoming challenges and experimenting with different materials, resulting in a rewarding experience that pushed our fabrication skills forward. Here’s a detailed breakdown of our journey:

Step 1: Setting Our Skill Level and Choosing a Design

We started by determining the difficulty level we wanted to tackle. As beginners, we decided to keep things simple and opted for a 2D design that could be extruded into a 3D shape. After browsing designs on Thingiverse, we selected a dragon head shape that we found intriguing. The original design, however, required modifications because it included small cuts and details that wouldn’t work well for CNC machining.

Step 2: Refining the Model in Rhino

To address these issues, we imported the dragon head design into Rhino. Using Rhino’s editing tools, we smoothed out the problematic cuts and ensured the design was ready for both CNC machining and 3D printing. This step was crucial in ensuring a successful fabrication process.

Step 3: 3D Printing the Master Positive

Next, we 3D printed the chess piece to create a master positive mold. The results were promising, but we noticed that one side of the print lacked some finer details. This insight helped us refine our approach for the next step.

Step 4: Scaling and CNC Machining

After addressing the design imperfections, we moved the file into Carbide Create to prepare it for CNC machining. We scaled the design to be able to fit within the 3.5” x 7” wooden block and created toolpaths for cutting. Due to the size of the details we had to switch between 1/16” and 1/8″ end mills during the cutting process. We almost encountered a problem when we ran out of time cutting out the pocket cut outside of the shape but fortunately we were able to start from where we left off on the previous cut.

 

Step 5: Silicone Molding

Under the guidance of our instructor and TAs, we created silicone molds in class by calculating an estimated volume of the space taken up by the silicone and measuring out the appropriate amount of part A and part B and mixing it together.  We poured silicone over the CNC-machined positive and allowed it to cure over the course of a day, producing a durable and flexible negative mold. Although there were some spots that did not totally cure, overall the mold turned out well, capturing the intricate details of the design.

 

Step 6: Casting the Chess Pieces

With our silicone mold ready, we began casting the chess pieces. We estimated the volume needed to create our shapes out of polyurethane, which came out to around 40 mL, and mixed an equal amount of part A and part B together before casting it into our silicone mold. We experimented with different colors to add variety to our set:

• The first piece was left white.
• For the second piece, we added a single drop of red dye to achieve a light baby pink color.
• The third piece accidentally used a slightly higher ratio of formula A, which created a bubbly texture and caused the piece to expand more than the previous attempts.
• On our fourth attempt, we miscalculated the amount of resin mixture, resulting in an incomplete cast. This trial-and-error process taught us the importance of precision in material preparation.

Key Takeaways and Reflections

This project was a valuable learning experience, highlighting the importance of iteration and adaptability in prototyping and fabrication. Some of our key insights include:

1. Planning Matters: Careful scaling and editing during the CAD phase minimized errors in the machining and printing stages.
2. Precision is Key: Small changes in dye ratios or material amounts had significant impacts on the final product.
3. Teamwork is Essential: Collaborating and learning from peers and mentors made the process smoother and more enjoyable.

Cost Analysis

Assuming 50g of PLA used: 50g* $0.02/gram = $1.00

Assuming 300 Watts usage for 40 minutes and electricity costs $0.12/KwHr: 0.2 KwHr * $0.12/KwHr = $0.02

Assuming $20.00 per 38.8 oz of silicone mold making: 3.65oz *$20/38.8oz = $1.88

Assuming $139.61 per 128 oz of polyurethane: 4.05 oz * $139.61/128 oz = $4.42

Labor Cost: $15/hour * 8 hours * 2 employees = $240

Total Cost: $245.44