Foam Mold Casting?

I was reading a website where a guy was using a sand casting technique to
make Al. parts.
He would create the part in Styrofoam and then coat it with some drywall
compound slurry, then buried it in sand within a larger box. From the
pictures it looks like the molten Al. would replace the foam, I assume via
burning it up, and the part was made.
What is this process called?
Thanks
Reply to
Pal
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"Lost Foam Casting", I believe.
Be careful what you use for the slurry -- some things (like Plaster Of Paris) have too much water, and decompose at the aluminum temperatures, releasing steam, and perhaps generating dangerous geysers of molten metal.
Find the *right* materials to use, for safety, if no other reason.
Enjoy, DoN.
Reply to
DoN. Nichols
The lost foam casting is a version of the lost wax method which has another variation in lost plastic casting. One of the attempts with lost foam is the reduction of the amount of plastic that gets burned out of the mold. Wax and plastic need to be removed by heating before the metal is poured into the mold and the foam just reduces the amount of plastic that is used.
-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!
Reply to
Bob May
Also, the foam doesn't have to be coated before casting. You can take the foam pattern (with a sprue), cover it with loose, dry sand, and pour. The molten aluminum pretty much "instantly" replaces the foam so that the sand never has a chance to collapse.
With lost wax, the wax pattern is used to make a mold by coating it with a shell and then melting out the wax, leaving the mold.
Yet another difference is that with lost wax, there can be a master mold which the wax pattern is cast from, allowing many, many copies. This can be done with foam, but not by the ordinary hobbiest. Commonly, lost-foam is one-shot - if it doesn't pour right the first time, you make a another pattern. Repeat as necessary.
Bob
Reply to
Bob Engelhardt
Found this site quite informative in lost foam casting . The loose sand works well for small work but In casting larger forms I find it works well using green sand, less washout, also a bid deference in the foam used, the denser foams take more detail but also take a lot to burn out when casting aluminum. Ben
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Reply to
Mac

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