On 14 Feb 2005 10:22:36 -0800, "Jim" wrote:
I need to fabricate some rubber parts for a custom air intake system
for an automotive application. The function of the rubber parts is to
connect various pieces of steel tubing together with an air tight seal
and still allow some flexing. The parts also need to be able to take a
hose clamp without tearing. I'm thinking a shore A hardess of about 40
should be adequate. It's a non-production, hobbyist application.
Temperatures will unlikely reach over 350F. The end result will be
something similar to a coupler used for turbo/intercooler plumbing, but
that's not my intended use.
There are lots of sites out there that offer products for MAKING
silicone/urethane molds, but very few talk about products for CASTING
the product. Those that do, have not returned my e-mails. Maybe
because I don't want to buy 55 gal. drums of their product. Can anyone
offer some help on who might carry a product that will satisfy my
requirments? Thanks for any ideas.
Vinyl plastisol might work. It's a liquid that you dip a heated
(350F) metal mandrel into. The material forms on the mandrel until
the mandrel cools or you pull it out of the stuff. Build of up to
1/8" isn't hard to achieve. If you want more build, use a mandrel
with an internal heater to keep its temperature up. There's probably
a limit to this, I haven't explored it.
You then bake it at 350-400 for half an hour or so and then strip it
off the mandrel. Those football-shaped squeeze pounches for pocket
change were made with it. I've made sparkplug boots with it. For a
part of very convoluted shape, as a bellows with deep corrugations,
you might need to make your mandrel so it can be disassembled for
extraction, but the stuff does stretch some.
It's available in small qty from Industrial Arts Supply (IASCO) in
Minneapolis. Its natural color is an insipid milky white like a
condom, but IASCO has a few dyes including black and red. You mix
the dye with the liquid before use.
http://www.iasco-tesco.com/
You might not find the stuff on their website, but they have it.
Some of the two-part RTV's can handle up to 650F, but I don't know if
they're tough enough for your application. Those are probably the
mold-making materials you mentioned.