Quote: (Otterman @ 01 Mar. 2009, 18:26 )
Heya Vermis, the process is called investment casting. The output of Todd Boyce's machine is a delicate kind of plastic. To make a vulcanizable / sturdier pattern, he dunks the plastic original in enamel with some extra feed channels.
I originally thought the output of the machine was a kind of plastic but I'm now pretty sure the material is a very hard wax - similar (if not the same) as jeweler's wax.
I deliver the part to the investment caster where he attaches a wax sprue (you can see the attachment point on the autocannon). It is then suspended by that sprue in a molding compound slurry (within a thick metal flask) about the consistency of buttermilk. That then hardens into a rigid mold around the part with the sprue sticking out the top.
The whole thing is then stuck into a kiln and heated to a thousand-plus degrees until the wax model and the sprue are vaporized and burned out of the mold, leaving an empty cavity. Metal is then poured into this mold through the hole the sprue left behind (I think this pouring happens within a vacuum chamber but I'm not positive) and cooled.
The flask is pounded on with a hammer which shatters the mold material inside (which basically breaks apart like a very fine sand packed tightly) and the part is extracted and cleaned of any remnants.
If all goes well, you have a more valuable metal copy than the original wax copy - which is why it's called an investment cast. And like all investments, there is a chance that it won't pay out in the end.
Todd
 
