Question – assuming TileGal and I could could make a plaster mold set (like she’s done of vegetables for her clay art tile business, could we melt ~12 lbs of aluminum in her kiln to pour into the mold?
The part is ~13″ diameter; a 9″ disc about 3/8″ thick with (28) perpendicular “fan blades” around the periphery – they’re ~5/8″ thick at the root and 1/2″ apart; 3″ high and 2″ wide.
Yes, it’s a big heat sink.
Is this possible? The part is purely for a thermal testing sample and for fit-up. For the pattern, I have a FDM’ed plastic model, I can add % for the shrinkage of the aluminum.
What aluminum? What plaster? Only need one . . .
Forrest – pushing the extra mile at work
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You want old pistons for the alum, that much I do know.
Got nuthin else. I used to sand cast so plaster is beyond my range.
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Hey, just one you COULD sand cast it.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations
"If Brains was lard, you couldn't grease much of a pan"
Jed Clampitt
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Try Duckworks Magazine, an online boatbuiling site. Rob Rohdes-Szudsy did an article there on casting aluminum in one of the july issues. How the heck do you post a link?
Wow - got it; a three part series - http://www.duckworksmagazine.com/09/columns/rob/06/index3.htm
Thanks tons!
Forrrest
Never used plaster, several years ago I did aluminum casting into sand molds with my son and daughter's boy and girl scout troops. The kids made their own sand molds...roughly 90% silica sand, 10% clay, and just enough water (very very very little water) to bind.
They pounded their own molds, the adults used a local shop to melt and cast the aluminum while the kids watched.
You're doing an open casting, so I don't see why plaster wouldn't work. But I'm by no means an expert or even knowledgeable on plaster as a mold material.
I've read that a lot of aluminum casting is done by making a styrofoam model and then packing it in sand. The styrofoam evaporates as the aluminum pours in.
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That's how Saturn in TN does their engines.A La Carte Government funding... the real democracy.
That's how we did it in collitch.Carve the piece out of pink or blue styrofoam.Use rubber cement to glue on additional pieces.One the piece is the way you want it, add a sprue and some vents.Lay the piece flat in the center of a wooden frame. Pack sand around it. Make sure you have that sand really packed tight.Now flip it over, lay another wooden form on top of the first, and pack the sand against that side.The "sprue", is a piece of styrofoam that is centered on the best place for the entering molten metal. It will be shaped like a long narrow funnel.The vents are just 3/4" by 3/4", or 1/2" by 1/2", pieces of styrofoam that lead back to the top of the green sand/mold again.The molten metal instantly displaces the styrofoam, when it is poured.Done right, the sprue is in a place where it will not only fill the form the fastest, but will spread evenly to the extremes.The vents will be placed so that the molten metal does not get slowed down or stopped by air bubbles, on it's way to the extremes.Once the metal is poured, allow to cool for about 10 to 20 minutes.Knock the sand off. Cut off the sprue and vents. And clean up the casting as you wish.As for the sprue, a classmate once had a large but thin casting to be done. He set up several sprues and linked them all together so they would all get molten metal at the same time. Had a spiderweb of vents going. His casting was successful.....You are always welcome at Quittintime
Yup, that's exactly how we did it.
These folks may have a book or two that might be helpful ........ "technical books for experimenters, inventors, tinkerers,
mad scientists, and "Thomas-Edison-types." http://www.lindsaybks.com/ Got this one http://www.lindsaybks.com/bks6/cookbook/index.html a while back for my sis who's a chef .......... is gunner writin' on the side? ;o)
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I ve used this web site to help with replicating pieces.
http://www.backyardmetalcasting.com/index.html
interesting thread...
we cast gold & brass in a "lost wax" process and do use plaster...
the short of it is...
make a wax of the part you want to cast... adding sprews like was mentioned.. now cast the wax into a block of plaster... let dry... then heat the block in an oven... the wax will drain out leaving a void in the plaster... the molten metal is then poured back into the plaster... we used a centrifuge (sp)? to spin the plaster block so as to force the molten metal into all the details... after it cools you bust away the plaster... cut off the sprews... grind & polish...
so yes we cast in plaster all the time... think all dental casting is done in plaster
p
I'll throw this link in here for you.
I can send you a PDF of the whole thing if you don't want to sign up to see all the pics.
http://www.instructables.com/id/Quick_cheap_and_dirty_aluminum_melting_furnace_s/
there are some other aluminum casting projects there also.
Lemme know if ya need more
http://www.discoverlivesteam.com/magazine/127/index.html
here is another link. Also would like to see this thread rally and see more post's.
The company I work for pours 120,000 lbs of Alum. per month. Aluminum should be poured at about 1350 degrees F. Make sure the plaster is completely dry or you could have an explosion. Liquid Alum. is like a detergent it eats up metal so what you melt it in and pour from is important. Air pockets in your plaster mold will cause those areas not to fill out. Drill tinny holes in the plaster mold where you think air will pocket. I would pre-heat the mold before pouring. 1) less shock to the plaster and less chances of it cracking and 2) the mold won't pull heat out of the liquid Alum. which can cause short pours. Alum car pistons are usually a high temperature alloy and a little more difficult to work with. A good alloy for what you are doing is 319 Alum. alloy. A metals distribute will sell you a bar which is about 20lbs. Alum shrinks a lot. To eliminate voids caused by shrink make the mold area that you intend to pour into about an extra 4" tall and about 2-1/2" to 3" wide and usually round so it stays hotter longer.