This is Michael Knight at CASTALDO. We make a rubber that you can
use to inject at up to 50 or 70 psi. But please read further before
even considering this approach.
You CANNOT compress the air trapped inside a mold, not at 50 psi
anyway. At 10,000 psi, maybe. You are trying to solve this problem
with a sledge hammer.
So what you need to do is RELEASE the trapped air. That is, give the
trapped air a way to get out ahead of the wax.
The modifications you need to make in the molds are called air
release vents. They are cuts in the rubber from the extreme points of
the pattern area to the outside of the mold. That is, to the open
air. If your wax is entering the mold at the bottom of the shank,
then the extreme furthest point might be at the tips of the prongs.
You’ll know because these areas are the ones that are not filling.
And you’ll need to keep the vents open with a very thin dusting of
talc. Apply sparingly from time to time and try your best to keep
the talc out of the pattern area. If it gets into the wax pattern it
will cause porosity in the final casting. Not to mention degrading
the surface finish.
You can increase the pressure or choose a wax that is more fluid,
but those are just further refinements on the sledge hammer idea.
About the high pressure rubber: It’s called CASTALDO Titanium Label.
You can read more about it on our web site at:
But remember that hot wax forced out of the back of a improperly or
insufficiently clamped rubber mold at 50 psi might do nasty things
to your skin. Set up some sort of plexi shield to work behind. And
use gloves and common sense, too.
I’d be happy to send you – or anyone else out there who is
interested --a small free sample to try out.
Please let me have you delivery address – no P. O. Boxes – and
your telephone number – UPS insists on it.