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Investment casting

I took a lost wax class many years ago and am thinking of investing
in an investment casting machine at Rio Grande. I can’t find any
demonstrations of how they work. I have been through the youtube
videos which don’t seem very helpful and really want to see whether
the expense of one of these machines is worthwhile. Looking at the
Dura-Bull vacuum investing and casting machine.

Google Dura Bull casting demo

Hi Barbara;

If you live in an area that has a program with casting equipment
(park district, arts center?) then you could probably walk in and
talk to the instructor about it. All vacuum and casting equipment
works on the same principles, so at least you would have an idea of
where to start. It’s an expensive hobby, so check out all the
physical locations you can before you commit. It isn’t just the
casting equipment, it’s supplies, maintenence, a vacuum table (if it
doesn’t include one. some do) a kiln that reaces at least 1500 deg.
F, flasks, etc.

All I can say is. it’s worth the price to use the shop I’m in at the
park… even though the equipment is older, it works and it’s good


Happy Newyear by the way -)

Why don’t you ask the people of Rio Grande? They never leave a
question unanswered and try to be as helpfull as they can be.

Working with this machine is straight forward and for sure not

The left side is the investment area and the righthand side is the
casting area.

Under the bell jar.

Fill your flask and put a rubber flask extender on the top of your
flask. A piece of duck tape will to aswell.

Make your investment slurry and place ut under the bell.

Place the right handle in position "investment table.

Switch the machine on and let it go to max vacume (+/-30bar) If you
wish you can tap the table with the bell to make the investment more

The airbubbles start to show and at a certain level the investment
will rise (thats the reason of using flask extender).

When the bubbling stops, switch of the machine and release the
vacume by placing the handle in “vacume release” Are will enter under
the bell jar. Wait untill the gage shows zero and then remove the

Remove the flask gently and let it cure without touching.

Complete your melt-out procedure and keep the flask inside the killn
until you’re ready to cast.

Setup your casting machine.

You can use small flasks by using the flask adapter and the silicone
solid flask gasget. The flask will be placed on top of the casting

Or you can use perforated flasks which sink inside from the top of
the casting machine. (ask Rio for more explanation for the size of
the flasks and gasgets) If you use the perforated flask you need
silicone flask gasget.

Place the handle in the “casting chamber” position.

Get the hot flask out the killn with the flask tongs and place it in
or on top of the casting machine depending on which flask you use.

When using the machine with flask on top of the machine, make sure
that the hole in the flask plate and solid silicone flask gasget are
lined up to give the vacume full access to the flask.

Place your flask with the sprue opening upwards on the solid
silicone flask gasget so that the flask completly covers the vacume

Melt your metal with the torch, the temperature of the flask will
not drop that much.

The exact time of melting your metal depends on howmuch you have to
melt and how you melt it (torch or melting furnace).

Switch the machine on and let the vacume buiild up as far as it go’s
Place your crucible above the flask and keep it nice molten and
ready to poor.

Always calculate more metal in order to form a nice button in your
investment opening.

Poor it in the flask with the machine still running, don’t swith it
off at this time.

Watch the color of your metal changing from white to first red.

Switch off the machine and release the vacume.

Take the flask out or start with a second flask.

Some people like to cool the flask completly and others quench in
water after all color of the metal is gone.

The writting of the handlings in matter of fact takes more time then
all the handlings together.

It’s realy uncomplcated and straight forward. Get familiar with your
equipment and practice is the best way of building up knowledge with
this procedure.