For the final project, we decided to create octuplet owl pawns.
The project began a little rocky where we fell behind after we were both in COVID quarantine for the first week of the project. Once we were both released from COVID prison, we began the project by finding a chess piece file on Thingiverse. We loved the owl pawn chess pieces and moved forward with preparing the mold files.
Using Meshmixer, we created the mesh file of our owl halves and brought them into SolidWorks. In SolidWorks we added pins and a plate to the back of the owls. After we had a file from SolidWorks, we used Fusion360 to set up the tool path and settings for the CNC router. This was the tedious part, but after we had all of the files created, we moved on to 3D printing!
We hit quite a few roadblocks while 3D printing. On our first attempt at a print, we realized the scale of our mold was terribly small. Then, once we had a mold that we thought was the correct size, none of the printers were open for us to use. Several days later, we finally found open printers in the morning, but we again underestimated the size of the mold. Once we made our final adjustments, we ended up with two great halves of the mold!
To create the mold, we first created a box around our 3D printed molds. Using the box of indeterminate size method, with cardboard and hot glue we attempted to create a water-tight cavity to pour the silicone. Our first attempt to create the boxes had several leaks (we tested with water first). A lot of hot glue and a few adjustments later, we were able to successfully create a mostly water-tight mold.
We mixed the silicone with a 1:1 weight ratio of part A to part B, poured it as carefully as possible into the mold halves and waited overnight to remove the box and 3D printed base from the silicone. Unfortunately we had a few air bubbles, but luckily our mold lined up great and we had a super minimal seam on the owls.
Once we were ready to finally create our owl family, we mixed the resin in a 1:1 volume ratio. We used cardboard on the sides of the mold with rubber bands wrapped around to hold the silicone halves together. We were shocked that it only took 5 minutes for the resin to cure! It was also super interesting that the resin was so hot in the process.
With our beautiful owl children, we post-processed using 120 grit sand paper and then 400 grit sand paper to smooth out the seams and imperfections on our owl pawns.
We were so pleased with how our family turned out!
Overall, we created a super cute family of owl pawns with minor imperfections. For the future, we would spend more time ensuring the silicone mold has as few bubbles as possible. For post-processing, we learned that to remove excess resin from the parts easily, when the piece is still hot, an X-Acto knife will work wonders on the small bubbles that form.
Cost Analysis
3D printed bases: The 3D Printer OS tool gave a cost estimate of $1 per mold half of filament. For machine use, we would estimate it would cost $5/hour to print, and we printed for about 5 hours total. This would cost $27 for printing.
Cardboard and hot glue: Assuming that the general household owns a hot glue gun or could access one without buying it, we won’t include the cost of a hot glue gun in the analysis. For cardboard and glue, we would estimate about $2 of material costs.
Silicone: It is about $360 for 2 gallons of silicone (part A and part B). We used about 2 cups of silicone. This would be about $45 for the mold cost.
Resin: It is about $145 for 2 gallons of EasyFlo Liquid Plastic (part A and part B). We used about $18 in resin (480 mL of resin used).
Mixing sticks, cups, sand paper: We would estimate about $2 for materials for mixing sticks, cups, sand paper and other disposable items.
Labor costs: We spent about 8 hours in total. If our hourly rate is $25/hour/person (from our tutoring rate), then we would have about $400 in labor costs.
Total cost: $494! The vast majority of this cost is from labor (~81% of the total cost). These are some expensive owl children.
