Re: Casting WAX in silicon moulds

From: Chuck Alexander (
Date: Fri Jun 11 1999 - 22:38:59 EEST

At 01:32 PM 6/11/99 -0400, you wrote:
>We inject wax into silicon rubber tooling for investment casting. What
>we have found is that it is best to use the wax from the foundry that
>the parts are going to. Its seems every foundry has their own wax. It
>has never been a problem in having them give you enough for the project.
>A problem of injecting wax into soft tools, is that it has to be melted.
>This can create sinks in the heavy sections as the wax freezes. Also,
>after a few shots the mold retains the heat and it takes much longer to
>pull a part, as much as an hour... ...Ross Gates

Also you can use a "chill". The basic idea is you have 2 molds. The 1st mold
creates the "chill" which is an undersized version of the final geometry.
For instance the chill might have all the surfaces offset 0.25". The chill
is then held in the 2nd mold (with core prints) and injected around to
create the final shape.

As the name implies, the chill acts as an internal heat sink, reducing the
amount of heat left in the mold after demold. Also, with a uniform 2nd skin,
you can better predict shrink and should be able to eliminate sink.

Chuck Alexander

Solid Concepts Inc.
Rapid Prototyping Software & Services
ph. 661-257-9300
fax 661-257-9311

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