Heyy!!
When we started our final project, we wanted to do something that is cool and elegant but also has a significance attached to it. Solid and symbolic, we settled on the Moai from the Rapa Nui structures. They were built to represent important ancestors and hold spiritual authority over the land. Most of them face inland, supposedly to watch over the people. On top of the cultural weight, they’re also kind of a technical flex: carved from volcanic rock, some weigh over 80 tons, and nobody really knows how they moved them. That mix of power, mystery, and precision felt like the right energy for a chess piece. Our version? Five of them. Slightly scaled down. And definitely not carved from volcanic rock.
So we started by looking at Thingiverse to find the most appropriate Moai design. We landed on one that was clean enough to work with a single-body Moai that had decent geometry and didn’t look like it was going to explode if we tried to CNC it or 3D print it.
“Model first, pray later.”
We pulled the STL file and then remodeled it to get a 3D print. Once we flattened the bottom part of our chess piece and added the mesh to the design, we went in to print the 3D piece. Darshon scaled it well and sent it into one of the Bambu lab printers. So for our gate 1, we knocked off the 3D printed object well. It looked amazing and was ready to be submitted.It was solid. We were asked to reduce the size by half an inch on the 3D print for our gate 2. So we got to that. The tutorials they posted were solid which helped us for our gate 2. Darshon and Sandeep got working on the design while I was there at the printers to print the piece.
One major hiccup we faced was that the Bambu lab we were using had the filament disposal nozzle stuck, So we had to wait till the next day to get that printed and submitted.
“Divide and conquer.”
Next task was to mold the 3D print from gate 2, which meant cutting our 3D model in half and fixing a baseplate and adding alignment pegs. We used 0.4” and 0.375” circles just like in class, one set extruded, the other set cut so we could align the mold later without guessing.
Following this, we had to make our silicon negative so we designed the other half for the CNC cut. Finally cut the piece using the 1/8th of the drill bit with the alignment pegs by importing the STL into VCarve, followed the instructions, and… watched the first attempt fail spectacularly. The roughing pass chewed into the model like it had a personal grudge. We swapped tools, adjusted boundaries, and tried again. Eventually, after tweaking the tool paths and switching to the 1/8” bit, we got a clean cut that took longer, but it was worth it.
“Hot glue, hope, and cardboard.”
We hot glued the cardboard walls around the model and poured in the silicon (70g of Part A + 70g of Part B). We were going to use this for making our mold. The calculated volume was roughly 150 cm³, but we knew better than to trust the math entirely. We rounded up. Always round up with silicon.
Once both halves were done, one 3D printed, one CNC’d we got to work on the silicone mold. We mixed Part A and Part B in equal amounts, adjusted the total based on what we actually needed, and poured it into the cardboard box we built around the piece. Nothing fancy. Just measured, poured, and waited. A few hours later, the silicone set clean, and the mold was ready for casting.
“The silicone era.”
Once the molds were ready, it was time for the polyurethane. The math said 35 cm³ per piece, so naturally we used 40 cm³ just to be safe. We started dying it reddish pink (because of course we did) and went onto adding some purple, yellows and blues and poured them onto their respective molds.
First pour? Looked a little crooked but if sanded it would look nice. The rubber bands were good tight enough, and the two mold halves held well. The resulting Moai looked like it had seen things. It worked.
“Finishing touches: sharp blades and sandpaper.”
Once all five pieces were out, we sanded the bases flat and finally processed it with a 120 grit paper, sliced off the extra flash with an X-Acto knife, and gave the Moai some dignity. Every piece had minor imperfections, but honestly, That gave them character. They weren’t perfect but they looked and felt like they belonged on a chess board along with the knights and queens.
COST BREAKDOWN:
- 3D printing (half-model): ~$1.40
PLA filament: ~$1.25
Wood (2×4): ~$1.10 - CNC machine time (5 hours): ~$6.15
- Cardboard boxes (5 total): ~$3.40
- Hot glue (10 sticks): ~$1.15
- Silicone (280g total): ~$8.00
- Polyurethane (310g total): ~$17.30
- Measuring cups, sticks, rubber bands, X-Acto knife: ~$18.90
- Labor (26 hours @ $7.25/hr): $297.30
Total: ~$356 and five stoic, heads that now live rent-free on a chessboard.
Clean working space
