Week 7
Molding and Casting
Part 1: CAD Design
This week, I wanted to mold and caste a little turtle! I started off with designing the turtle in Fusion 360. My planned process was (1) 3D print the (positive) turtle with a high precision resin printer, (2) create a silicon mold (negative) of the turtle, and (3) create a caste of the the turtle using wax = turtle candle!
I first designed the turtle itself:
I then enclosed the turle in a box, where I'd be able to pour the silicon (or other material) to make the actual mold:
Part 2: Creating the Mold
Using a Formlabs resin printer, I printed out the turtle to a high degree of precision (.05 mm), so that the lines weren't really visible. It was printed without supports, and I then put into a IPA wash for 10 minutes to clean up the liquid resin. After drying it off, I put it in the FormCure for 30 minutes to cure. Then I sprayed Ease Release 200 on it to help the mold (described below) release.
After finishing printing the positive mold, I poured in the material to make the mold and let that set. Specifically, I used SYLGARD 184 Silicone Elastomer Kit, which is a platinum-cured silicone elastomer. This is a two part kit mixed 10-1 ratio of base to cure. After mechanically stirring, I put it in a vaccuum chamber and de-gased so that all the bubbles were released. I then slowly poured it into the 3D printed turtle postive mold, and de-gased again to make sure all of the crevices were fully filled. Finally, I placed it all into an 80 degree oven for 1.5 hours to cure. After curing, I took it out, let it cool to room temp, and removed the negative mold. It came out quite nicely with no bubbles!
Part 3: Casting the Turtle!
Finally, I took the mold off of the 3D printed structure, giving me the negative of the turtle. Using some candle wax I got off Amazon (here), I poured the heated wax into the mold and put it in the fridge to cool:
I took the turtle out of the mold (and promptly dropped it and broke off a fin oops), and was left with a little wax turtle! If I get my handle on a candle wick, I'll put a hole in the shell and turn it into a candle :)
