Resin Casting

[jaxenro]

I was going to cast some resin parts for my little motorcycles. What do you that cast smaller parts use for mold making and casting resin? If possible I want to avoid the need for vacuum chambers

Edited August 13, 2018 by jaxenro

[Art Anderson]

14 hours ago, jaxenro said:

I was going to cast some resin parts for my little motorcycles. What do you that cast smaller parts use for mold making and casting resin? If possible I want to avoid the need for vacuum chambers

Professional resin-casters do use vacuum chambers, but only for "degassing" the Silicone RTV rubber after mixing in the catalyst (that rubber is almost like a moderately thick pancake batter in its liquid form.  Air bubbles in the cured resin, if close enough to the surface of the master,  can actually "bulge', as virtually all catalyzed RTV  Rubber shrinks ever so slightly in volume, giving pressure to any airpocket or bubble (if close to the surface of the mold "cavity",  even a small, trapped airbubble can actually force a "dent" into the surface of the casting.

You may be confusing a vacuum chamber with a pressure chamber or pot though.  Professional casters (and I was one for 12 years) use pressure chambers to hold two-part molds in, while the resin itself cures and hardens--that goes a long, LONG way toward eliminating tiny airbubbles against the surfaces of the mold cavity, which will appear as anything from almost miniscule "pin holes" to rather serious gaps.

I used to use Campbell-Hausfeld pressure pots that were manufactured for propelling paint into spray guns, for the likes of painting houses and other buildings   The ones I had were rated to 150psi, but I set the pressure regulator on my shop aircompressor tank at 75 psi, which left me a considerable "safe zone",  and yet did the job of crushing small airbubbles into oblivion before the resin hardened.

Art

[Art Anderson]

As for the resin,  nothing beats Urethane resin--which is what most all professional aftermarket model car resin-casters use.