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Vacuum casting


#1

Hi all

I’ m looking to purchase a Vacuum caster . Maybe the perforated
flask type a 5" dia ± . 3 cfm or 5cfm ? What is the best/good
make or model ? What to stay away from . Any and all
recommendation , suggestions or advice would be appreciated

Thanks Lou


#2

I highly recommend the Neutec j-2r casting machine.(RIO,& other
sources I expect) I finally have near perfect results most of
the time compared to the disasters I had on a regular basis with
my previous system (perforated flasks with an electro melt
furnace.) The problem for me was that by following recommended
pour and flask temperatures -they just didn’t work. Much trial &
error was incurred before I had moderate success but the enclosed
melting chamber makes the difference in my opinion. The extra
expense paid off for me. … Darryl


#3

Darryl:

I have been curious about the system you are using. How long have you been
using it? What kind of problems have you had with it and is it expensive to
keep the system up and running. Thanks

Kenneth Gastineau
@Kenneth_Gastineau1


#4

Check out the web site for Macaw.
They are good friends of mine, and decent people to do business with.
I have known them for years.Kerry has been in the Jewelry tool business
for at least 10 years.He holds the pat.for the Pave’tron dia.texturing tool.
I buy all my tools from them! You can meet them at
the shows.I think their schedule is in the site.

Their address is www.macaw-tools.com
They have everything you need.
Sincerly,
Greg Alexander
Jewelry “spoken here”


#5

Hello Kenneth
I’ve had my system for two years now and enjoyed a high rate
of success. As with most new procedures, there was some trial and error
but not much.
There is some extra cost keeping things operational (inert gas &
tank, graphite parts) but that’s about it. Basically I can’t say I’ve had
any problems worth mentioning- especially compared to my previous vacuum
chamber / electro-melt process. That was very tempermental with a much
greater margin of error.
Hope this was of some help.
Darryl


#6

Darryl:

Sounds encouraging. I currently use a melting furnace capable of
melting 20 pounds of bronze (loud and hot). I have been wondering
what I would do if I ever needed to simplify some of our casting
procedures. Sounds like you’ve found the solution. Thanks

Kenneth Gastineau
@Kenneth_Gastineau1


#7

I have a small vacuum caster from Rio. It has a single table used
for investing and casting. Usually I just use it for investing and do
my casting with my Neycraft centrifuge. A friend suggested that I
use my vacuum for casting rather than the centrifuge. He told me that
when he does it, he puts the heated flask on the vacuum table, set
for casting, melts his metal in the sprue hole of the flask, rather
than in a melting furnace, or crucible, and when it is all molten,
turns on the vacuum pump, still keeping the torch on the metal so
that there is no danger of it freezing.

That is the first time I ever heard of that method, and it seems
that it would be a very efficient way of doing casting.

Have any of you tried melting your metal directly in the flask, and
if so, have you had good dense castings?

Alma


#8

Investment begins to break down at somewhere around 1350F As a part
of that process sulfur dioxide gas (SO2) is liberated. SO2 is
absorbed by the metal and will result in gas porosity in the casting.
Since most metals we cast melt at much higher temperatures you will
definitely contaminate your metal by melting in the investment. Once
the SO2 is in the metal the only easy way to get it out is refining.

James Binnion
James Binnion Metal Arts


#9

it might work for small, single item castings, but not for larger
ones… when I cast, I’m usually doing between 100-250 grams at once
and it takes too long to heat that up… the flask would cool down
too quickly, even with the heat on top, plus, as it melts, little by
little, it would ‘weep’ into the mold, but cool before it gets all
the way in without the vacuum (I do filigree. lots of nooks and
crannies), which could block the pathways for the rest of the
silver. So, if you are casting one small piece, that doesn’t require
much metal, that may work. I would take the flask out of the kiln a
little hot in case the bottom cools quicker than the top. Even with
those, I would be concerned about metal ‘dripping in’ in bunches,
rather than one continuous pour. it could leave weak points where the
subsequent ‘layers’ meet.

Jeanne
jeannius.com


#10

Hello Alma, An old casting method is to burn out the flask, bring it
down to casting temperature and then place it on a heat resistant
surface. Melt the metal in the flask as you say. This works best if
you have about three small sprues rather than one large. Then the fun
begins: jam a previously cut in half potato over the flask with the
cut side down. The hot flask turns the water in the potato into
steam, the steam drives the gold or silver into the flask and you
then eat the now cooked potato. Or you can, as your friend said, use
the vacume to draw the metal down into the flaskbut you don’t get to
eat the potato. Have fun. Tom Arnold


#11

Alma,

Making a crucible in the end of a flask works fine IF you use
several small sprues instead of one big sprue. With small sprues the
surface tension of the molten metal will keep it from running down
into the sprues until you turn the vacuum on. This is the same method
that is used for steam casting.

I have a whole chapter on steam casting in my book “Lost-Wax
Casting: Old, New, and Inexpensive Methods.”

On the other hand, with vacuum-assisted casting you are limited to
atmospheric pressure for the force on the metal driving it into the
mold while with centrifugal casting you can create more force on the
metal perhaps with an extra turn when winding the spring. Plenty of
folks use vacuum assisted casting but I have the impression
personally that you can get more force to fill fine detail with
centrifugal casting. Others have said this as well.

Fred


#12

To do this, I would think that you would have to sprue as for steam
casting - many small sprues leading to a larger (melting) cavity on
the top and to the model on the bottom. Yes/No? Thoughts?

Debby


#13

That’s an interesting thought, but I just can’t see how that would be
a good idea Alma. I’d think you would often get a little grain of
metal at the bottom that plugs the sprue hole and doesn’t melt or
you’d get your metal molten, but not up to the desired temp. It seems
to me like you’re just asking for trouble doing it this way. Plus I
don’t think the investment was designed for those melting
temperatures. It seems like it’s much more controlled if you melt
your metal in a hand crucible (or hand furnace) and pour when it’s
ready. You can either check the metal temp or roll it around in the
crucible to check if ready before you pour. Personally I prefer to
spin them, same as you’ve been doing, anyway.

Mark


#14

Thanks for all the thoughtful replies to my question about melting
the metal in the flask and using the vacuum.

I can see where there would be some possible problems, and also the
need to use small sprues. As I usually have several wax models
attached to a main tree sprue, I will continue to use the vacuum for
investing, and then use my trusty centrifuge for casting. Never had a
failure with it yet. Alma


#15

There are so many variables involved in casting, so many little
things that can effect your results. I think any of us who cast
should pick a method, centrifugal or vacuum, and then work out the
bugs in our system until we consistently get good results. Then
stick with your method and be happy with your good castings.

In my experience, everyone who casts does it a little bit
differently. It may seem like two casters are doing it exactly the
same, but you can see in the results that they’re not. You can drive
yourself crazy trying to put your finger on the variable that is
creating the problem. So when you find what works for you, don’t
monkey with it too much. Just thank your lucky stars.

Mark