Buiding vacuum casting equipment

Jewelry Discussion
1

Hello,

I am new to this list. I joined because I wanted some information
about buiding my own vacuum casting equipment and learning to cast. I
have never done silver castings before, so I have been reading as
much as possible. I intend to cast musical instrument parts from
sterling and hopefully gold later on. It is typical within the higher
end musical instrument makers to vacuum cast parts. My volume would
be very low. The size of the item I want to cast first is
approximately the size of a large man’s ring.

I do musical instrument repairs. My shop is equiped with a heavy 10
southbend lathe, manual milling machine, metal shaper, small cnc
mill, torch and other metal working tools. I purchased a large bell
jar and I have the means to fabricate most of the things I need…I
think. for the vacuum machine. My first question is, how much vacuum
do I need? Can I use a venturi type vacuum pump?

Lastly, are their any Jewlers on this forum close to Syracuse or
Auburn NY willing to guide me? I promise I won’t be competing with
you as I have no desire to make jewelry, just instrument parts.

Thanks!
Matt

2

Well my dear friend,

It is not very difficult to make a vacuum assist casting machine.

What you need is a very good oil rotary vaned high vaccum
pump,capacity minimum required is 100 liters per minute, or more but
not less, to remove air by vacuum of your bell Jar which should be
10 inches in diameter by 12 inches in height approximately. 12X12
inches of bell jar will need 300 liters per minute capacity of pump
to remove air with in one minute.

First you will have to take a mild steel sheet (plate) of 10 mm
thick, and 12 inches by 12 inches square or more according to your
bell jar diameter which will be used to remove air from your
investment slurry. you have to on your lathe,phase one side of this
plate perfectly flat, and make a 15mm hole in the center of this
plate.

Then weld a 3 inch diameter by four inch height pipe of steel under
this plate ( which is the top of your casting and investing table,
two in one,) below the hole in the center of the plate, but before
welding this pipe ( a steel flask of 3" X 4" can be bought ) weld a
half inch dia pipe or the size of the the flask(3x4) on which the
vacuum rubber pipe will fit, to the 3X4 inch flask at right angle in
the center of the flask, the flask’s open end will be closed with the
rubber base former of the 3 inch size, which you can buy at the
jewelery supply store,.this will ensure proper vacuum seal.

You will have to buy a silicone rubber sheet, four to five mm thick
of the size of this plate and make a 15 mm hole in the center of it,
this rubber sheet will ensure proper vacuum seal while casting and
investing.

This way your casting and investing table is ready, now you can weld
four bolts under this plate as legs of the required height
approximately one inch. this casting and investing table which is
ready is to be fitted on a metal or wooden box, which has a five inch
hole in the center of its top so that the 3x4 inch assembly under the
plate is accommodated inside this box ,whose size should be in
proportion of the your casting and investing table.

The flask you will use for this above casting machine will be solid,
you will have to use a perforated sheet of thin card board as liner
inside the flask. you can bye a 15 mm dia punch to make holes in a
sheet of thin card board and make a perforated sheet, to line your
solid flask, this flask will have to be filled approximately five mm
less, for the vacuum which will be applied form below the flask and
the seal is proper with the edge of the flask is clean of investment.

You have to connect the vacuum rubber pipe to the casting table you
have made. you will have to fit a vacuum release valve and a vacuum
gauge in between the vacuum rubber pipe.from vacuum pump to the
casting table. You can fit this vacuum release valve and the vacuum
gauge on the box of the casting table. make proper connections.and
check for the vaccum is not leaking from any joints.

Hope this will be of your help.

Many more suggestions like this will be on your way form my many
Orchidian Friends to guide you to success of your vacuum casting
machine project.

Best of luck.
May all be free from all difficulties.
May all be free form ill will, hatred, animosity, anger.
May all generate good will, love, peace and harmony.
May all be happy and healthy and liberated.
Strive to be Happy

Umesh

3

Matt,

Are you sure that you want to go through the hassle of building
machines? Get in touch with a local Dental Lab and see if they have
already invested in a vacuum casting machine. Many have and cast
parts for dentistry on a daily basis. I’m sure that they would work
out a small fee for casting a pattern for you, especially if you
provide the invested pattern and materials.

Regards From Your Kentucky Friends,
Craig A. Pickett, RG CDT
Technical Support Manager
Whip Mix Corporation

4

Vac casting set ups are really easy to build, all you really need is
a bell jar (that you already have), a rubber pad and table to set it
on, a vac pump, an inline filter, a 3 way ball valve, and a steel or
table for the flask to set on. The only tools you need are a hacksaw
and a drill press to build one. I’d get a 5cfm rotary vane pump,
there’s tons on ebay. All the other parts you can find at the local
hardware store or at McMaster Carr. Email me and I’ll send you pics
of my set up.

On the other hand, there’s more to casting then just having the
equipment. Unless you are really driven to master it yourself and are
willing to invest the time and money making the necessary mistakes,
I’d suggest farming out the casting work to start, and focus on
creating and selling your instruments. If you build enough demand,
you can always move the casting in house later.

Harry
www.harryhamilldesigns.com

5

Thank you to those that have replied to my novice questions. I’ve
picked up some very valuable already.

Umesh, Thank you for your very thorough reply. I need to go over it
line by line to make a drawing of the rig. I already have a friend
who thinks he can obtain a suitable vacuum pump. Having never cast
before, the one thing I am a bit unclear about is how the vacuum
works with the flask and the investment. From what I gather the
investment is porous enough to allow the vacuum to pull/airpressure
to push the molten silver in the mold without additional venting or
runners to the cavity of the mold. Is this accurate?

By the way, I have quite a bit of experience making aluminum molds
for a small injection molder that injects thermoplastics. I plan to
make a mold and inject wax into the mold for my first lost wax
castings. I have a small CNC machine I built so making the molds is
pretty easy. Just time consuming. I have a great deal of blue
machinable wax that I can melt, but I’ve noticed that it shrinks a
great deal as it cools. Is this the case with the wax used for lost
wax castings? Can I use the machinable wax, or should I buy something
different?

Thank You,
Matt

6

Hi Matt:

I did my undergrad metals work at Syracuse University (SU). There is
a very well equipped shop out at their ComArt facility on Comstock
road, just south of campus. (Across from the graveyard.) The woman in
charge of the program is Barbara Walter. (Sorry, it’s been…a
while. I don’t have her current phone #) When I was there they
weren’t doing community classes, but if you gave her a ring, she
might be open giving you the nickel tour, and/or hooking you up with
a student who might be open to a bit of side work. They have (or had)
a home built vacuum investing table, along with a shockingly
effective vacuum casting rig built out of a few bits of pipe and a
shopvac. (for investing, you need the highest vacuum you can get, but
for casting, flow volume is far more important than ultimate vacuum,
so a beefy shopvac works surprisingly well.) The SU program is one of
those very quiet little shops that never makes a lot of noise, but a
whole lot of very interesting people have been through there over the
years. If you get a chance to get in and take a look, go.

If you can’t link up with Barbara, I still have a couple of
blacksmith buddies out Utica way, and at least one of them has a
small casting rig. He’s very good at improvising things, so he could
certainly help you.

Contact me directly if you need.

Regards,
Brian Meek.

7

Matt:

You will need a good vacuum pump for vacuum degassing your
investment and for vacuum casting. You nee to be able to pull 29+
inches of mercury vacuum. Vacuum punps used in the heating and air
conditioning trade are very suitable for this application.

You can build you own vacuum degassing table which will also serve
as a vacuum casting table. You need a reasonably soft rubber to
place on the table upon which you place the bell jar. I recommend a
small ball valve (about 1/2 inch) with an external filter (an
automotive gasoline filter works well for this) to prevent debris
from entering the system when tou open the system to relieve the
vacuum.

You should be able to find a good vavuum pump for abour $200.

If I can be of further assistance, please email.

Howard Siegel

8

Oh my- This takes me back. 25 years ago my ex husband and I built our
own vacumn machine. We were so proud when we put the bell jar on and
tuned it on. We breathlessly watched the gauge hit 30 lbs and
cheered. Then, slowly it dawned on us that we had forgotten to out
a relase valve on it!

It took a day to relase.

Jo
ps I still prefer vacumn casting to centrifugal casting.