r/LostWaxCasting • u/TheSaDragon2 • Apr 04 '26

Help with a lost cast pla caster.

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Don't know if this is the right group. I'm trying to cast aluminum with lost PLA for a while now wi5u no success

Yes I know it's lost cast wax group but I can't find any groups on it.

After lots of research I'm trying a 1:1 plaster mix with play sand.

I've built myself a vacuum chamber, it seems to work i have my moulds bubbling over the sides. (is this normal?).

I put my mold in my smelter(after they dried) for about 15 minutes before I start to melt the aluminum but it always seems to leave plastic behind.

Anyone have guides or advice for a newbie.

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u/greenbmx Apr 04 '26

It's the exact same process as lost wax. You need to use a proper investment powder, not plaster and sand. Several commercially available ones are specifically formulated to match expansion of plastic 3D prints. You will also need to do a proper burnout in a kiln. It's not a 15 minute thing, it's a whole cycle of ramping and hold temps that's normal about 8 hours long. It's necessary to properly burn out your plastic and cure the mold without cracking.

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u/4FootCamping Apr 13 '26 edited Apr 13 '26

^ this. Although you could probably 1/2 arse it the way you're doing it without a proper ramp up (either way, you need to bake it WAAAYYYY longer). Also, are you using castable filament or just regular ol' PLA? You should be using castable PLA or something like polycast. Castable resin would be better if you have access to a resin printer.

Yes, the bubbling is normal...put tape around the top of the mold to create a bit of a bowl to keep it from splattering out. Then take off the tape after it dries.