Small production casting of a complex item - lost foam?

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Alan J. Richer

G'day. folks. Just been thinking about an idea and want to bounce it off the assemblage.

I tinker with old Brit cars, and on the Land-Rovers I tinker with it is becoming impossible to find certain electrical components - for example the fuel tank senders on early positive-ground vehicles.

The basis of these units is a pot metal/Zamak casting with has external and internal detail. These were obviously pressure-cast in a steel mold originally and literally cranked out by the millions I have no doubt.

Well, my shop is not that well-equipped.

It occurs to me that the best way to do this might be lost-foam casting - make up the foam pieces in lots and then cast up aluminium from there.

My question is - how to make up the foam blanks? I can easily see myself making up a plaster or other mold to turn out the foam sections risers and all a half-dozen at a time - but what to use as a pourable foam that will "go away" properly under the ingress of the metal?

Opinions other than "you're an idiot" gratefully accepted.

Thanks - Alan


Well-Known Member
Oct 30, 2007
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I don't know if this will work for what you want to make but why not make one up and get a rubber mould made for it or make it yourself with the RTV silicon and then make wax copies and use this for lost wax casting


Well-Known Member
Apr 22, 2008
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its the "internal" part that concerns me. the bits that you want hollow. hi temp silicone is okay for zinc (so ive been told) and plaster works well (from experience) but you must get it totally dry! lost wax rather than lost foam would be better... lost foam "sounds" great but in practice does have some limitations. a pic of the part would be good for further advise.

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