Metal Casting Zone

I am new to casting and forging.

today i started to b uild a home mmade melting forge for aluminium.

I am producing 50+ challange coins, they are 3 inch x 10mm with a 3D image on one side and writing on the other and are going to be cast from Aluminum.

I have carved the first one from wax as i was planning on using the lost wax method.

but befor i melt my work, how to i reproduce it??

i know i make a mould and cook it but then the only way is to smash the clay mould to get it out?

do i have to sit there and carve 50 of these (took about 2 1/2 hours for this one and about 4 trys to get it just right)

i had thought of two moulds one of each sideof the coin in clay and when set together form the full coin, but then how to create a seal to hold the moulten ali??

any help whould be great

What you need to do is make a mold from your original wax carving. Then you use that mold to make 50 wax coins. You then immerse each wax coin in a refractory material and let it set up. From there you burn out the wax and this makes a cavity in the refractory material that will be a seamless mold for which you can pore in your molten aluminum. When the aluminum solidifies, you then shatter the refractory mold material to reveal your aluminum coin.

You can also connect a number of wax coins together using connecting rods made of wax into a wax coin tree. Whatever is wax is going to be solid aluminum when finished, so you'll need to cut it all up to get your individual aluminum coins if you do this method.

As you think about this notice also that you'll want to make a solid funnel shape out of wax so that when the wax is burned out of the refractory mold a cavity in the shape of a funnel will be left behind for poring your molten aluminum into.

That is the absolute basics of lost wax casting. There numerous details I skipped over, but you sound like the type who'll fill in what I left out.

In addition to the basics of making the molds, there are two methods you may want to look into regarding how much detail will need to be transfered from the refractory mold to the aluminum as the aluminum solidifies. Which are, vacuum casting and centrifugal casting.

Vacuum casting simply sucks the molten metal into a porous refractory mold and centrifugal casting simply pulls the molten metal into the refractory mold by centrifugal force.

Hope this helps. =)

I just reread your question and I just wanted to add some thoughts on making the main mold that you will use to make the 50 wax coins.

What is normally done is to make this mold out of rubber. There are different types of rubber and different types of methods for casting and or curing the rubber.

Once cast, what is normally done is to cut the rubber into two halves. So in other words, if you had your original wax coin that you carved incased in a solid block of rubber, you'd use an exacto blade and cut your wax original out of it and at the same time cutting the rubber block into two halves.

You'll most likely damage your original wax carving with this process, but once you have the rubber mold, you can make 100s of duplicate wax coins.

You don't have to make it from rubber or room temperature vulcanizing compound since your coins will have no undercuts so you can make it out of something hard like polyester resin or plaster that has been coated with a sealer to seal the pores of the plaster.

Do not stick your artwork in one of these hard molding methods without doing a test first! Cuz you could end up getting your original stuck in one of the halves of the mold you're trying to make and if that happens you could up with a loss of your artwork.

=)

does it have to be a special kind of rubber??

i have a few tubes of silicone rubber will this be ok or will that melt from the wax!!

if i was to use a solid compound (plaster or clay) how whould you recomend to seal the pores and also to seal the 2 half's together to stop run-off.

Actually, silicone rubber, also known as RTV (Room Temperature Vulcanizing) can stand up to fairly high temperatures! It can stand up to temperatures well beyond the melting point of most waxes.

The problem is going to be air bubbles. If you have a vacuum chamber you can stick your mold into it and remove the air bubbles and you'll be fine.

Then again, you may be able to put on a thin coat and simply press out all of the air pockets that form. You'd then apply thicker coats onto that without concern for the air pockets.

But yep! That will work!

As for your other question, SILICONE! =D Just smear it on with your fingertips. Or, I've never tried it, but PVA (Poly Vinyl Alcohol) might work.

=)

check out the oomoo silicone from this site www.smooth-on.com/
it is how i was doing my coin that is posted under lost crayon oomoo silicone on this site. they also have a release agent available.

Yeah! Smooth-On is an excellent company for mold making supplies!

Another is, Douglas & Sturgess at www.artstuf.com

I met the owners years ago, very nice people who understand the meaning of struggling artist!

=)