We have experimented a couple of times with doing some aluminum casting, and each time we get better results. This time we re-designed our fire brick kiln to burn some coal and get a boost from a cheap blow-drier. We also purchased an actual crucible and casting sand from Larsen Foundry Supply in SLC. We had much better results from this pour than we got the last time we tried to burn out a 3D print.
The Statue, “Female Torso, Esquiline Type“, was downloaded from thingiverse. The model was generated from 140 pictures of the original in the Louvre captured by Cosmo Wenman. The original artist is unknown. You can hear more about Wenman and the process on NPR All Tech Considered.
The statue was printed in natural PLA with a single wall, and only 2% 3D honeycomb fill.
We packed the 3D print upside down in refractory sand, and pressed it around the piece to create the mold.
It was a challenge to get the kiln hot enough, but we were finally able to get a silvery pool of aluminum in our 4 lbs. crucible after adding lots more coal and skimming the surface.
We poured the aluminum slowly at first, then quickly as the plastic began to melt and burn. I was a little afraid that the bubbling plastic would create a geyser of aluminum, but it just sputtered a bit.
After the burning stopped, and the metal had a chance to cool, we carefully wiggled the piece free with a twisting motion, and were finally able to see the result. A truly beautiful piece, made from scrap, plastic, and fire.