west_bend3 wrote:
> I followed vinces direction to the letter in his first book about
> useing aluminum epoxi for making a mold. I followed devcons
> directions to the letter for mixing harding and machineing. But on
> the first injection with LDPE the mold completey failed. Should I use
> the Ti epoxi. I dont have my lathe finished yet and wount have it
> finished till next spring. Can anyone help me. I need this problem
> retcified imedietly. Thanks
>
Difficult to be certain without more information, but this might be a
temperature related failure. Most epoxy formulations begin to soften
around 350º F, if not lower temperature, and you're probably in that
temperature range when injecting LDPE. I'd suggest trying genuine JB
Weld, an aluminum reinforced epoxy that claims to retain strength to
above 400º F.
Beyond that, you might find it works better to make your model with a
three-step process using high-temperature RTV silicone to produce,
first, a mold, then a positive, and finally cast low-melting alloy
(solder, lead alloy, or pewter) to make the working mold. The RTV will
take the temperature of the casting, and the casting will, with luck,
have the strength and temperature tolerance for your injection machine
(and it'd relatively inexpensive to make the mold this way -- $10 or so
for the RTV at a parts store, and another $10 to $20 for the alloy
you'll cast).
--
If, through hard work and perseverance, you finally get what you want,
it's probably a sign you weren't dreaming big enough.
Donald Qualls, aka The Silent Observer http://silent1.home.netcom.com
Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.
http://groups.yahoo.com/group/gingery_machines/app/peoplemap/view/map
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