Re: Casting WAX in silicon moulds

From: Bruce E. LeMaster (
Date: Fri Jun 11 1999 - 17:26:37 EEST


We have been producing wax patterns via vacuum casting for 6 months or more and have had very good luck with it. We build SL patterns, make a silicone mold, heat the wax in our MCP unit and cast
it under vacuum. The foundry we used for our most recent parts was very impressed with the patterns. They took the wax patterns and placed them on a tree just like they would if they had shot
the wax parts in house.

There are several issues that need to be addressed when casting wax. First, temperature is the major problem - not hot enough and the wax will chill before completely filling. To hot and it
takes a very long time for the part to cool for demolding - the silicone holds the temperature very well. We preheat the molds and have played with various cooling techniques to speed the demold
times. We have experimented with chillers (wax plugs) which definitely help if you have a part with an area of large mass. It seems that there is no universal recipe for casting the wax in
silicone. Instead, each part geometry may take slight adjustments of initial pour temperature, temperature of mold, demold time, and use of chillers.

One concern that our customer had was how good the surface finish would be on the wax parts - they wanted a very smooth cast finish. We found that the surface finish of our wax patterns is
better than that achievable from the investment casting process. Since our SL pattern was highly polished, the wax patterns come out just like the pattern.

I've posted three pictures to our web site that show some of the wax parts, the castings, and the SL patterns. Have a look and see what you think.

Good luck,

Bruce E. LeMaster

Rafael Santillan wrote:

> I got a part from Z coorp machine, but I need some more for a customer to use as investment casting, and I dont want to melt this one. I have already created the silicon mould from this one.
> Does any body has experience in to cast WAX instead of urethanes in a silicon mould, to produce investment WAX prototypes to produce later iron or aluminium parts in sand.
> If so what type of wax ?
> Does it work fine ? does it wort ? I will appreciate any hint or advice
> best regards
> *********************************************************************
> ** Rafael Santillan, Ph.D. Mech. Eng. Office Phone: 52-42-112623 **
> ** Analysis and Numerical Simulation Fax: 52-42-169963 **
> ** Proc. Energ. **
> ** **
> ** CIATEQ Centro de Tecnología Avanzada **
> ** <> **
> ** **
> ** Address: Calzada Retablo 150 Email: **
> ** Queretaro,Qro. / MEXICO ZIP 76150 **
> *********************************************************************
> For more information about the rp-ml, see

Applied Rapid Technologies Corporation
265 Cambridge Street, Suite 100
Fredericksburg, Virginia 22405
(540) 371-1100 / (540) 371-4100 fax

For more information about the rp-ml, see

This archive was generated by hypermail 2.1.2 : Tue Jun 05 2001 - 22:51:52 EEST