By: Justin Xia and Ethan Liu
For our final project, we chose an owl pawn chess piece from Thingiverse. The STL file is by budgiesarecool(https://www.thingiverse.com/thing:709768). Our workflow combined 3D printing, CNC machining, and molding to produce four finished silicone pieces.
Preparing the STL File
We started by downloading the full owl pawn STL and checking its sizing by printing the complete piece in PLA. This helped verify proportions before committing to the mold design. Once we were happy with the scale, we split the STL into a front half and a back half using Tinkercad. This gave us two clean positives to build molds from.
Making the Physical Positives
The back half of the owl was 3D printed. The front half was machined from wood using the Carbide 3D Nomad 883 Pro. We processed the STL in Carbide Create Pro, set up the toolpaths, and cut the front positive with detailed contour and pocket passes. After machining, we sanded the surface to clean up the tool marks so the mold would capture smooth geometry.
Creating the Silicone Molds
With both positives ready, we built mold boxes for each half and poured silicone over them. The molds cured with tight seams and aligned well. Since the halves matched cleanly, assembling them for casting was straightforward.
Casting the Final Pieces
We cast four owl pawns: two red and two white. For each pour, we mixed silicone and added pigment. The molds filled cleanly, and once the pieces cured, we trimmed the parting line to get a smooth silhouette. The finished pawns kept the feather details and the round base from the original STL.
Cost Breakdown
The PLA used for the test print and back half was about 80 grams ($20 for 1kg), so that cost about $1.60. The wooden block for the CNC half cost ($4.12 for 4 feet of 2×6″ wood), so $0.34 for 4 inches of 2×6″. Silicone is $13.50 for 20.46 oz., so for both molds, we used 206mL or $4.60 worth of silicone. The polyurethane is $46 for 72 oz, and we casted 4 70mL models, so 280mL of polyurethane cost $6.31. Consumables like tape, hot glue, and sandpaper added another $0.50.
Labor was 16 hours total. At $10/hr, that’s $160.
The total material and labor cost for all four chess pieces is $186.85 ($46.71 per owl)!
Overall, this project was a lot of fun to create. The molds fit together well and the final products have a lot of the original details!
