G Scale Model Train Forum banner

RTV casting tools...looking for advice

5354 Views 16 Replies 7 Participants Last post by  rkapuaala
I'm looking for recommendations regarding what I should be looking for to develop a casting capability using RTV molds. I have the mold master...so I'll need to be able to make the mold and then make the parts with the mold. I'm not interested in what materials to use...yet. I know RTV comes in a variety of "qualities". But this request is about the tools needed.

I think I need three "tools":

a. Paint pot, in which to do the mold making or part making

b. Vacuum pump
[*]to pull air out of the RTV when making the mold from RTV and [*]When using the finished mold, to pull air out of the resin after it's poured/forced into the mold [/list] c. Presure pump to force the resin into the RTV mold

Is this correct? If so, then what are the specs I'm looking for?
[*]How many inches of vacuum dose the vacuum pump need to pull? [*]How much capacity does the vacuum pump need?...How fast does it need to pull the air out of the paint pot....10 seconds...or 10 minutes? [*]Same for the pressure pump....how much pressure does it have to put out....how fast does it need to pressurize the paint pot? [*]I've found paint pots up to 2.5 gal in size. What size is used by most modelers? Where does one find one in larger sizes...say 5 gal? [*]What gauges are needed on the paint pot to measure vacuum or pressure. What kind of valves? Where does one get the valves. [/list] I'd LOVE to see a photo or drawing on how one of these things is set up. Does anyone have one?

Lastly...some questions related to size. If I wanted to cast a 3' long passenger car side, how does one size this stuff up? What kind of paint pot would work and how much bigger do the pumps need to be.
1 - 1 of 17 Posts
Hi everyone,

Follow-up question to Mike's question...

I have been casting parts for about two years... simply doing, as Burl calls it "ambient casting". I do not vacuum pump my RTV. Mostly I have one part molds, some "glove" type molds.

My RTV molds seem pretty good, the level of detail matches my original model quite well (e.g. rivets, undercuts, etc). If I get a good pour of plastic, its near perfect match. About 2/3 of the time I get bubbles that I have to go back and fix with small batches of Alumilite (usually not related to mold details).

Based on this... my question, where would I get the biggest bang for my buck: pressure pot for the Alumilite or vacuum pump for RTV? I think historically I have read that degassing the RTV is the best thing, but my experience seems to be that RTV is quite forgiving, and that the resin is the problem area...

Any thoughts?

See less See more
1 - 1 of 17 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.