Back in high school I took a summer college course where we cast aluminum. I have wanted to do it again ever since. I bought all of the Gingery books but could not get motivated to put it all together. When I found several web sites using cans as a cheap alternative I could not resist. I wanted to plate for my Model A to honor my Dad who died when I was 17. He is still with me and I wanted something for this car that showed it. I am not through yet but this was the first pass today using a plaster mold. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o> <o> </o> I started with a patter made from luan and cut out on a scroll saw.<o></o> <o> </o> I had tried to make a foam pattern but it stuck and the first pour was ruined because of the gas release. <o></o> <o> </o> The last, because the mold fell apart was better. At least now I know it will work.<o></o> <o> </o>
Cool. I'm goin' to try that sometime too. Seein' post like yours is encouragin'. What size is your plate? Smokey
looks good.. tell me more about the failed "lost foam" you did.. fwiw.. if you have sufficent draft. you could likely make a negative copy of the luan (in plaster of paris) and when the plaster of paris dries completely you could make a pour into the plaster.. (the plaster of paris has to be fully dried though( no moisture present) where are you in pA?
The plate is 5x9. I cut out the frame of the plate with the scroll saw table tilted at 15 degrees. The letters and design I cut straight and then molded in the relief with drywall joint compound. I then covered it with some craft sealer. I then made a plaster cast with the intention of making a foam positve that I would use fro lost foam casting. I coated the casting with PAM spray but it was not enough of a release agent to let it the foam pull free. I tried melting the foam with acetone and when it did not I tried to burn it out. Once it was burned out enough to keep the wife from killing me I baked the palster in the oven to dry it out. At this point I had nothing to loose. I think the bubbles in the first poor were caused by the renmaining foam and acetone reacting to the hot aluminum. At least I know I can move forward with my second attempt.
For "lost Foam casting",the metal is poured into the foam, which is packed in sand. You don't have to try and remove the foam,or burn it out first. Some people seal the foam with white glue, to improve the surface texture in the finished part.
Congratulations on getting as far as you did! Success with foam relates to the actual foam used, and how it's vented. Unless you're preheating HOT, like 2-3X your oven's capability, there's gonna be foam residue. If your plaster mold resembles a bottle, one way in/out, then the gas cannot escape fast enough when the metal touches it and becomes entrapped in the casting. When a professional foundry uses the metal to burn the foam out, they're doing it on a loose packed sand mold that's permeable. Meaning the foam gas can escape thru the mold. With plaster, the mold's pretty well sealed. If trying the foam again, make your mold, set up outside with a torch on the mold. When it's really f-ing hot and the foam is gone, time to pour. Don't let it cool down, that's how mold cracks start. Ceramics heat up better than they cool down. Your mold burnout and melting process need to happen all at once. Timing is a huge part of the art of foundrywork. By preheating that severely, the mold doesn't suck the temperature out of the melt so quickly and cause instant solidification. By remaining liquid a little longer inside the mold, it gives foam gas trapped in the melt an opportunity to escape. No matter what you do, there will be some smouldered plastic residue in that mold, and it will react with the metal. If you do this again, do yourself a favor. Find a place that'll sell you 50lbs of olivine sand and a few quarts of air-hardening binder. Don't reinvent the wheel. You can make a bad casting with a good mold. But you can't make a good casting with a bad mold. Good luck
What I was trying to do was make a plaster cast on my wooden pattern and then pull multiple foam positives to cast using the lost foam process. What I have decided to do is pour directly into the plaster mold. I made a new pattern since the first attempt. I hope to make another stab at it this weekend.
some things to know about casting into plaster molds. 1 plaster gives off water at 300o and at about 1000o. 2 if you mix sand with the plaster (about 20%) your mold will be stronger, when its hot and will breathe better giving you less gassing problems. I dont know what you are using to melt your metal but it should be good enough to cure your mold. just do it slowly. Pogo
Well round two was less of a success than one. I used a larger can for the crucible and could not get the aluminum hot enough. It solidified in the can and the mold only partially filled. I pull what did pour out and tried again but the plaster was cracked and the mold failed. I plan on using green sand for the mold on the next try and finding as small of a can as I can for the crucible.
good to see someone else enjoying the trial and error fun of backyard aluminum casting! I started with a two-can furnace, using a dishwasher blower and a soup can crucible- it worked, but my first melt spilled when I poked through the bottom of the crucible. I fabbed a 3" dia, 1/8 wall steel tube crucible, but it took so much more heat to bring it up to temp that it was too sensitive to outside temperature and wind. The melt solidified in the crucible. I saved up thirty bucks and bought all the stuff to make a refractory lined 5 gallon bucket furnace, reused the dishwasher blower. WOW!!!!!! what a difference! I just finished a bigger crucible today, and am working on a permanent ingot tray. (muffin tins suck) good luck!!!
Lurk at a pottery joint, I picked up this monster for $300. It will melt cast iron if given the time. The 300 may seem like alot but natural gas is cheap here, clean, and it's like instafoundry. If I ever get bored with it there are hords of losers making glass pipes that need this. I bought it from one of those artsy hippies.
Well I have not given up on casting but the recent tech on acid etching brass tags got me searching the net for etching aluminum. Same or similar to bras but a little mor violent as I understand it. I used the cheap inkjet photo paper-copier method in place of the PNP Blue for the stencil. The acid lifted the stencil in some places but in the end it gave the plate an aged look the I like.
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