Vacuum casting attempt

From molding systems to gating, what goes on at the molding bench will make or break a casting.
F.C.
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Re: Vacuum casting attempt

Post by F.C. »

If you can find a sturdy, plastic, tapered bucket with a sealable lid you can invest into that... devise a vent detachment nub you can connect an air nozzle to (think on the line of a sand blaster nozzle (where the suck end that pulls the sand through the nozzle is attached to the bucket lid vent nub) then set your sprued wax inside the bucket (pour cup attached/melted to the bottom), fill with mixed sand/plaster&water, close the lid, attach the sand blast nozzle hose to the lid nub and pull the trigger. Any air inside that bucket (and mix) will be pulled out. That's how I do it.
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Jammer
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Re: Vacuum casting attempt

Post by Jammer »

I had planned on using the vacuum chamber to pull out some bubbles but the plaster set up before I could get it in. It needs a new o-ring anyway.
quando omni flunkus moritati 8-)
Rasper
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Re: Vacuum casting attempt

Post by Rasper »

The stores in the US that sell plaster also sell plaster retarder. I use citric acid as there is no plaster retarder sold down here.

Richard
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Jammer
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Re: Vacuum casting attempt

Post by Jammer »

I couldn't find any citric acid so I ordered some from fleabay. Can you give me a hint at where to start? A teaspoon citric acid to a liter of POP? The large flask hold about 2 liters of plaster/sand mix. One liter of POP and a little less than a liter of fine sand, a little over half a liter of water. That's pretty close to thin milkshake consistency.
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Rasper
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Re: Vacuum casting attempt

Post by Rasper »

Grocery stores should have it. Women use it to make jelly and preserves and such. And to can tomatoes. Tennessee types of stuff.

Never add the powder to the plaster. Mix it with the water.

Here is what I arrived at through experiment with my plaster. (I use the same plaster always. Plasters differ in their characteristics.)

This is very scientific (Mexican science of course―down here we use what we have at hand)

I take a 3/8 inch nut (standard coarse threads) and fill that with citric acid. I mix that (not the nut; the citric acid) with 1/4 cup of distilled water in a plastic bottle. That is my stock solution, which I keep in the refrigerator. When I mix the brush-on coats of investment, I mix one part of that stock solution with 15 parts of water. That is the water I use in the investment. That mix gives me about 20 to 30 minutes.

R
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Jammer
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Re: Vacuum casting attempt

Post by Jammer »

Wow, that's a small amount. I would have used way too much. One nut full of acid makes a quart of water. I'm not sure I want to know how you arrived at using a 3/8 in nut?? I guess a 1/2 inch nut was too much. :lol:

They probably had it at the store, but the teenagers I got to help me looked at me like I asked for Plutonium. I went to Radio Shack and ask for ferric cloride, PC etching solution. "We don't sell anything like that here!" Then I reached up and pulled a bottle from the shelf. :roll: I guess that's why they are closing now.
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Rasper
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Re: Vacuum casting attempt

Post by Rasper »

I'm not sure I want to know how you arrived at using a 3/8 in nut??
I tried using a half inch nut but the plaster still hasn't set up and that was a year ago.

R
dallen
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Re: Vacuum casting attempt

Post by dallen »

Jerry hit walmart and look in the housewares area the citric acid will be with the canning stuff, to follow Raspers recipe be sure and get the crystals and not the liquid.

A course thread 3/8 nut full is probably equal to a 1/4 teaspoon full.
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Harry
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Re: Vacuum casting attempt

Post by Harry »

Nice measuring system, haha..

So are you going to vacuum cast Jerry? As in suck the molten metal up into the mold. Having a tough time wrapping my mind around that.

The tilt casting stuff Martin was doing seemed to me to be very interesting in the repeatability for large runs on parts but the molds investment was huge. IIRC he was using iron molds but not sure as that was a long time ago.
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Jammer
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Re: Vacuum casting attempt

Post by Jammer »

Vacuum casting is mostly used in jewelry casting or for small parts in brass and aluminum. Abby has been doing a lot of it for his small Steam Engines.
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