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Vacuum casting system?


#1

I’m looking to buy a used casting system. It’s an older machine,
just a motor, pump, slightly worn belt, and bell jar, (no gauge), and
the seller is asking $300.

In order to test it, we placed a cup of water under the bell jar. It
took more than a minute for the water to start boiling. I’ve read in
McCreight’s casting book that it should take within than 30 seconds.

Should I buy this thing?

Regards,
Sebastien Bailard,
developer, reprap.org - self-reproducing 3D printer project


#2

well no I just talked to rio grande and they have a system new for
500 item number 705-013 thanks Dan from West Cast :slight_smile:

Save up that extra 200 and get one new with a warranty and the
latest safety standards and you will not regret it…I buy some tools
used but casting should be new IMHO for plain safeties sake.

Teri
Silver & Cameo Heritage Jewelry
www.corneliusspick.com


#3

The water boiling test is more accurate than a gauge. Just
remember… when you boil water in the vacuum, you are condensing
water out of the moisture and into the pump oil. Change the pump oil
after that test.

John
The Jewelry Equipment Dr.


#4
The water boiling test is more accurate than a gauge. Just
remember... when you boil water in the vacuum, you are condensing
water out of the moisture and into the pump oil. Change the pump
oil after that test.

Well, John, you’re the expert. But that sounds counterintuitive to
me. While some hydrocarbons and solvents will mix with or at least
dissolve a little water, Heavier oils, like vacuum pump oil, and
water don’t generally mix too well, even when the water starts as
vapor, so I’d expect the generated water vapor to exit the pump in
the same manner as the evacuated air does… Until it’s exposed to
again raised air pressure instead of the vacuum, it would remain a
gas/vapor. That shouldn’t occur until the vapor has passed through
the pump’s piston or other pumping chamber and is at least headed for
the exhaust port, and once the pressure rises enough to condense it,
there’d then be an air current capable of carrying the aerosol mist
out of the pump, I’d expect… Plus, how is this test somehow all
that different from the normal use of a vacuum chamber for investing?
Normally, we boil the investment too. While that mix has lots of
investment powder in it, what’s actually boiling is the water, and
it would be generating about the same variety of water vapor as
boiling plain water. Yet we’re not advised to change the pump oil
after every time we invest… Are you sure this moisture issue is
serious enough to warrant discarding previously fine and usable pump
oil?

Peter Rowe


#5

Why do you did of oil-less vacuum pump for a casting machine?

Andy " The Tool Guy" Kroungold
Tool Sales / Technical
Stuller Inc
Phone 800-877-7777 ext. 94194
Fax 337-262-7791