Re: [rp-ml] Patching Silicone RTV Molds

From: Doug Groh <>
Date: Tue Dec 02 2008 - 23:01:35 EET

Silicon rubber molds have a limited life, however patching them does take a little finesse!

I have taken a quick bondo or urethane dupe from the part surface. Remember to use parting agent.
After removing the dupe, clean it up so it looks like the part surface desired. I would cut away any ragged edges from the mold, and make sure that the patch area has all been cut away so no old release agent is stuck to the patch area. Silicon rubber sticks to clean silicon rubber. Keep that in mind. If you place the dupe over the patch area visualize where your high spots will be and drill a hole in the tool. also drill another hole in the low area. The holes will need to be large enough to allow silicon to feed through them and to fill the area. The tricky part will be not having holding the dupe in place on the mold and not having any leaks. It is sometimes easier to just cast a new mold half. Patches almost never come out 100% clean and will most often need clean up on the part, cause you can not sand your patched area.

Doug Groh
President, 3G Services
Carbon Fiber Specialists
12254 Universal Drive
Taylor, Michigan
734-947-9458 Fax

--- On Tue, 12/2/08, <> wrote:
From: <>
Subject: [rp-ml] Patching Silicone RTV Molds
Date: Tuesday, December 2, 2008, 1:21 PM


Has anyone on the list had any good luck with patching an existing RTV
mold?  If so, how did you accomplish this repair?

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Received on Tue Dec 02 23:06:13 2008

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