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Vacuume casting (again?)


#1

I’ve been considering building my own vacuume caster, and an
interesting thought struck me. I was under the impression that
the presence of oxygen during the casting process is a potential
problem sometimes. Well, it also occurs to me that argon is
quite a bit heavier than air, and is readily available from any
welding gas supplier. So, it should be fairly easy to build a
"box" around the casting part, fill and fill it with argon.

Yea, the vacuume would suck down some, but it is 15$ for around,
150Cft. So who cares if we loose some?

Anyone have thoughts on this? Is this worth doing, or is the
danger from atmospheric O2 minimal?

                    -- Tom

,’| .-’’``-……–’;
/, ‘. …-’ , ,–…--’’’
< \ .--''' /| Tom Vanderputten
`-,;’ ; ; ; tvander@idi.oclc.org
__…–’’ __…–
…’ .;.’ Systems Development
(,
_…----’’’ (,…–’’ Unix hacker at Large
vi is my shepherd; i shall not font.

“People who are more than casually interested in computers
should have at least some idea of what the underlying
hardware is like. Otherwise the programs they write will be
pretty weird.” D. Knuth.


#2

I seen bronze foundries that use argon to prevent the molten
bronze from oxydizing. I’ve also heard of using Nitrogen for
this purpose. Be sure to research the health hazards before you
try it. I don’t know about argon, but I believe you can
suffocate without being aware of it if the Nitrogen levels get
too high.

Are you going to build your own vacuum pump? I built one from a
used auto air conditioning compressor that worked very well.
Evacuated the bell jar faster than the commercial versions. The
pump cost $3.50 without the electric motor.

Robin Casady
http://www.scruz.net/~rcasady/

Macintosh software for:
Managing URL Bookmarks
LX200 telescope control


#3
welding gas supplier.  So, it should be fairly easy to build a
"box" around the casting part, fill and fill it with argon.

Tom: it seems to me that the oxygen getting into the metal might
come largely from the torch. Using your torch you need to keep
the metal covered with a reducing flame to keep atmospheric
oxygen out, but if you’re melting alot of metal you need to use
an oxy/gas flame. I would think if you were going to use argon
you would have to use an electromelt furance to melt the metal in
an argon atmosphere. Maybe some of the others have some thoughts
on this…Dave

http://www.opendoor.com/stephensdesign/crystalguy.html
Crystalguy Art Jewelry, Magical Art Jewelry for the Enlightened Mind


#4

Tom said,

Well, it also occurs to me that argon is quite a bit heavier than
air, and is readily available from any welding gas supplier. So,
it should be fairly easy to build a “box” around the casting
part, fill and fill it with argon.

Anyone have thoughts on this? Is this worth doing, or is the
danger from atmospheric O2 minimal?

It’s reasonable to do on an industrial scale, probably not on a
1zy, 2zy basis.

Neutec from Rio Grande already does this. Don’t know if they use
argon or some other inert gas. You also have to melt the metal
via induction or electric arc.

“People who are more than casually interested in computers should
have at least some idea of what the underlying hardware is like.
Otherwise the programs they write will be pretty weird.” D.
Knuth.

Is that why most software is so screwed up?

Dave


#5

Hi Robin,

Could you please post some more info about how you built your
vacuum pump.

Thanks,

Nina
Nina - Silver Design, 9122 S. Federal Hwy, Suite 249,
Pt. St. Lucie, FL. 34952 : Toll Free:1-888-460-1800
URL: http://www.nina-sd.com : Email: @Nina


#6

Could you please post some more info about how you built your
vacuum pump.

It is fairly simple. I found a used Air Conditioner compessor
that came out of a large car. I believe it was a vain type
compressor. I mounted it on a board with a 3/4 hp electric
motor. I used the pully on the compressor and put a very small
pully on the motor. On the intake side of the pump I connected a
hose and particle trap to keep investment from getting into the
pump.

I would occasionally put a little vacuum oil into the intake
line to keep it lubricated. Oilers can be purchased that will do
a better job of keeping the compressor lubricated. They look
like compressor moisture traps, but add a little oil vapor to
the air entering the pump. You need to put something on the
exhaust to catch the oil vapor.

This pump worked amazingly well for over ten years until I
loaned it to someone who broke the particle trap and got sand
into the pump.

Robin Casady
http://www.scruz.net/~rcasady/

Macintosh software for:
Managing URL Bookmarks
LX200 telescope control


#7

Concerning the vacuum pump that Robin is suggesting. It can be
purchased from any used junk car yard. Ask for a Tucumsa or York
air conditioning compressor. By using the outtake of the pump it
can also be used as an air compressor pump for an air tank. I
have run my vacuum caster for about 3 years now at a cost of
$14.00 to build and I would put it againt any $600. to $800.
caster anywhere.

                                    Good Luck
                                     Ron Watts
                                     Gemcastle@aol