Instructables

Aluminum casting on the cheap?

For my woodshop class I am making a cane/"pimpstick" and I am making a custom head for it. I want to cast it in aluminum using the lost wax technique. would normal plaster of paris be a good material to use for the mold? the peice is about 3 cubic inches.

I was thinking about having two "fires" one to heat my aluminum and another to heat  the mold so it doesnt shatter. Is that workable?

P.S. It would be a one use thing so no need for anything expensive. I have literally 10 dollars to spend on this.

Thankyou,
  bud

rickharris1 year ago
1. Casting hot metal is dangerous! Take all care to prevent spills and damage to you and others.

2. Having said that: yes you could use Plaster of Paris - You will get a slightly coarser cast than with investement plaster which is much finer but better then with sand.

3. Yes heat your mould up prior to casting, mainly this is to prevent the metal solidifying when it hits old plaster. MORE importantly make sure you plaster is well dried out or it will create steam and explode in your face.

4. Lost wax is fine or you can use Styrofoam and just leave it in it will burn out from the hot metal. (mind the fumes).

5 A good source of aluminium is an old ally engine or parts such as pistons i.e. from a car.

Tough question that I don't have all the answers to but I do have experience in some of the areas.

When I was in school we had a metal shop which also had a small area for casting aluminium. It was cast in an oil/sand mixture that you would have to pound and compress into the two halves of the mould. The item that we wanted to cast had to usually be carved from a hard/rigid piece of Styrofoam, which the aluminium would burn it away when poured. We never had to preheat the moulds but the aluminium took a while to melt down in the forge so it was ready for casting.

In jewellery casting we often used the lost wax casting method. We always seemed to have a green or blue or red jewellers wax which was meant for carving. I'm believe it's a special harder wax that has a tendency not to chip and flake away when carving it. I'm not 100 % sure about what the investment was we used to make the mould around the wax carving but it looked like paster of paris ( you have to really vibrate and shake the mould so you get as little air as possible stuck to the wax carving, otherwise you get a nice little metal bubble attached to your finished casting). I do know we had to heat the mould slowly up to (insert correct temperature here that I don't remember) and we usually just turned the oven off when we were done and let it cool slowly. You want to get out all the moisture you can from the mould otherwise things could be breaking ans shattering. Once the mould was good we would have to mount it in a centrifuge, melt down the casting metal in a ceramic funnel type of a crucible (with a little bit of borax for flux... we were always casting silver) and then pull the pin and let it spin away. The next day we could toss it in some water and break away the investment from your casting.

Hope this info helps you out and be sure to search for helpful instructables on here such as

lost foam casting http://www.instructables.com/id/Lost-Foam-Casting-a-basic-walk-through/
or one of the many on lost wax casting