Howdy guys,


thanks for such a quick response. I've seen the Delrin melt before, and it
actually drips like a candle, so I'd just assumed it could be molded easily.
I'm waiting for the original parts manufacturer to send me a MSDS so I can
confirm which variety of acetal it is. Shrinkage of the part overall
dimensions is not a problem, the block's I was after are to be machined up
anyway If I can avoid casting a hollow piece I'm in luck, but its not worth
spending weeks on recycling what is probably 50 bucks of acetal, though I've
had trouble finding any stock here in Australia that fits my 4" x 2"
requirements, hence my idea.


I don't have a press in the workshop (my employers workshop) so pressurising
my mold is not a possibility, but bringing the mold down from flow temp to
room temp overnight could be done.


I'll have a go and post back, thanks so much for the help here guys.

Mark




"Dave Lyon" wrote in message
news:m_2Hf.548053$084.13001@attbi_s22...

"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.