"Ecnerwal" wrote in message
...
In article .com,
"Polymer Man" wrote:

My point is, without the specialized high pressure equipment used to
process thermoplastics, you're going to have some difficulties casting
this plastic. Uncontrolled shrinkage is the root of the problem.

I wonder if it would be at all feasible (largely depending on how fluid
the stuff is, and thus how good the seals would need to be) to make the
mold as a cylinder/piston arrangement, and either drop it in a shop
press or toss a clamp on it to provide some pressure. Obviously not the
same sort of magnitude as a high pressure injection mold system, but a
good shop press wailing on a small-area cylinder can get some reasonable
pressures going. ie, if the OP is making his mold 4x4 inches (by 2, or
however long - might be less fussy to make a longer block and cut slices
off of it), a mere 20-ton shop press could apply 2500 PSI, if the
plastic didn't all squeeze out past the piston.

--
Cats, coffee, chocolate...vices to live by

That's an interesting thought. If it's tried, better take some safety
precautions. Full body welding leathers, and a face shield at the minimum.

I used to work with a guy that was working on a molding machine. The nozzle
was still hot, and the plastic inside was too wet. It created a pocket of
steam that sprayed liquid plastic all over his legs. It had to be surgically
removed. It wasn't pretty even 20 years later.