Getting started in lost wax -- advice needed

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xo18thfa

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Years ago I bought these two books with the plan to get a lost wax foundry (and maybe sand) up and running some day.

Lost%20wax.jpg


"Lost Wax or Investment Casting" by James E. Sopcak

and

Bertha.jpg


"Li'l Brthea", A Compact Electric Resistance Shop Furnace" by David J. Gingery



Have any of you built any of this equipment? How's it working? A buddy of mine made some of Sopcak's equipment, says it works good. I saw on the internet a guy who built Gingery's furnace using soft fire brick rather than the castable refractory.

Many thanks in adavnce, Bob
 
Hi Bob, I cant help you with any of this but Ill cetainly be watching the outcome with interest...

Rob t 8)
 
Bob,
I have a bunch of refractory brick suitable if you need it. Let me know.
Sean

P.S. I have the tig welder up and running at our new house in the Northwest. Let me know when you want to start the boiler project...
 
Ive been trying to get into lost wax casting for a while. I did a pour today and got my first useable part, althogh I also got 8 failed parts in the same pour.

MY problem is in getting the metal to fill the investment. In my first attempts I simply poured the metal into the hot mold, but several people have told me I must use a vacuum on the mold. Today I tried to pull a vac under the flask and it did help a bit- the 2 good parts were the closest to the bottom.

Im going to get a couple pf the perforated flasks and make a steel cylinder to hold them so I can pull a vacuum all around the flask.

I have finally been able to make good waxes. The problem there was in getting good venting of the rubber.

It is a simple process, but greatly complicated in the details.
 
Ron,
I will be moving up to the perforated flasks soon as they are handy for a full tree of parts. I have had a few issues with vacuum on the solid flasks from time to time also.

My standard procedure when filling the flasks is to extend the flask with masking tape so it can be over filled. When I cut off the excess investment I carve a shallow depression then draw file the bottom of the flask that seals on the silicon gasket so I get a complete seal.

I usually size the flask to have a minium of 1/4" thickness on the bottom. I had an early pour blow through the bottom which was not fun.

Dan

 
I can only say Gingery's charcoal furnace works as advertised, but I have no reason to doubt any of his work.

RonGinger said:
Ive been trying to get into lost wax casting for a while. I did a pour today and got my first useable part, althogh I also got 8 failed parts in the same pour.

MY problem is in getting the metal to fill the investment.

I was told about lost wax years before I built my foundry, and it has always interested me. Since I was taught by a jeweler, he was mostly impressed about how little wastage of the base metal is involved. To me, I am more interested in the near net shape outcome. I have often wondered if you liberally vented your waxxes, if you could get by without the vacuum?
 
Jeff,
There is no reason that a system with a riser and vents would not work with lost wax and that is what is used with ceramic molds.

The advantage of vacuum casting is a single sprue can be used to fill most machine part forms. I pour silicon bronze and it is not as hard to machine as Al bronze but it is much harder than red brass or gun metal. That is why I am careful to put a single sprue in a location where it will be simple to remove.

As Ron pointed out rubber molds can be tricky to fill. The solution is to notice where the mold is not filling and make small cuts with a scalpel to make space for the air. This of course weakens the mold so cut a little then test again with the wax injector.

Metal molds like the cylinder mold that is my photo have a high degree of accuracy. I was worried about that mold filling but there is enough gap in the joints that there is not a problem. With metal molds you can hold the injection pressure until the wax is solid. This helps a lot if you are having problems with a thick section caving in with shrinkage.

You can see the size of the sprue I used for the cylinder mold it is used for both wax and bronze with a solid flask and vacuum casting.

The way I am now planning small bevel gears is to CNC machine wax gears and cast them. I am hoping the gears will shrink the same amount and run together with little or no fitting.

Dan
 

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