Instructables

Molding Aluminum: With Gravity Die Casting

It's expensive, untested and dangerous.
The idea goes like this. Start with a coffee can foundry, possibly powered with Biodiesel or Propane. Then design a mold for what you want to build using Autocad or some variant thereof. After it's finished, send the design to a machine shop to have it built out of steel. When you receive the permanent mold, melt the aluminum and pour into the mold repeatedly and often.

The idea seems like a good one to me, I'll be testing it soon enough using common screw clamps to keep the mold tightly secure.
Has anyone here done this? The closest I've come to doing it myself is pouring into a muffin tin.
The photo below is a picture of the results which was taken from another board found here, you'll need a login, the photos are located in the forum under Machining and Tooling.

Give me a shout if you dig the idea.

UPDATE 5/24/07

It works! Using my Harbor Freight Mini-Mill I cut out pockets in two pieces of 1018 steel, each about an inch deep, and four inches across. I then cut inlets in both pieces and welded some scrap steel U channel on the tops of both mold sections to form a pool enclosure for the excess aluminum to collect inside of and stay safely contained.
Then I lit the candle on my foundry and melted the aluminum while at the same time pre-heating the molds, (connected using C-clamps) in the oven. When the aluminum melted, I poured it and it instantly solidified. After about 2 minutes of running around in a panic I cracked the mold open. The detail level is incredible. Impressions made in the mold with a fly-cutter can be seen in the casting. The casting is bright, shiny, and seemingly devoid of any burs usually associated with unfinished aluminum castings.
I'll provide photos later of the test mold and casting.

cfreitas1 year ago
Sorry for being sooo late on this, but, is the author still active ? I would like to know more on this topic.

Thankyou.
hay_jumper7 years ago
Coming from a bronze foundry background, I would say that it's best to make a rubber mold of the item, and then to cast waxes in that. Once the waxes are chased, they could be sprued on a tree to cast many at once, even if it is in aluminum. Then it's a matter of investing and melting out your waxes. My 2 cents.
Hello hay_jumper,

I am 5 years late to ask this question about the rubber mould and casting wax, then making a tree for casting metal. Have you since the coment on "Moulding Aluminum" done an instructable? I would love to learn how to make repetitive mouldings. I would sincerely apreciate your answer and input.
Thank you very much,

Jesse M.
do you ship
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lowpro6 years ago
Make your mold and your crucible one and the same if you want to repeat parts. Cooling slowly will provide you with a stronger result. basically the slower it cools the better. So with a closed, well thermally insulated firing chamber melt the aluminum in a steel mold. You'll only use as much material as you need, and avoid the rapid cooling of pouring into a cold mold. I really like the idea of sandwiching a bunch of steel plates to make a mold. Cut out each layer and then drill and bolt them together. You can undo the bolts to release the part from the mold.
CameronSS6 years ago
If you don't know of/have access to a machine shop, you could try a place like eMachineShop. I don't have personal experience with an online machine shop, and I don't know what else is available, but it seems like an interesting way to get parts. They can do just about anything, it seems--laser cutting, CNC milling, lathe...

I'm not guaranteeing anything, as I have only heard of this service, and not actually used it, and it's not cheap, but it may be worth looking into.
Inspiracy (author)  CameronSS6 years ago
EXPENSIVE! I have their software and used it to price a couple of things and it's soooo pricey. It's probably that way because it's so darned convenient. It's much cheaper to just go to a small, job oriented machine shop, or buy the cheapest (harbor freight) equipment you can, which is what I did.
It's expensive because it has to be. For starters, you have the raw materials, which aren't cheap. Then if it is CNC milled, the mill has to be programmed. If it is lathe-turned, the CNC lathe must be programmed. If it is molded, the mold must be machined. It requires human input, and they are custom-building parts, after all. It is difficult to make a cheap one-off.
Inspiracy (author) 6 years ago
I've bought a mini mill and some tooling for it and I'm currently making my 1st "test" mold out of steel. The mold should be finished pretty soon, so I'll update this instructable with new pictures. Also, I'm leaning toward using copper for the molds instead of steel due to the fact that it's much easier to machine than steel is, and it should stand up to the 1200 degrees F that it takes to melt the aluminum. Whether copper or steel is used for the mold, it should cool down in under five minutes, allowing the mold to be emptied and re-poured quickly. This makes the process good for semi mass production.
There are several alloys in which copper is dissolved into aluminum much like table salt dissolves in water, so you may have a problem with the hot aluminum 'welding' itself to a copper mold. You can cool molds by running water (or other coolant) threw holes drilled in them.
Inspiracy (author)  jtobako6 years ago
Well then, it's probably best to just stick to the steel molds and use a releasing agent on them. Thanx
jtobako7 years ago
what do you need that many parts of?
Inspiracy (author)  jtobako7 years ago
Whatever, it doesn't matter. If it's made out of aluminum then it's game.
I can't think of a reason why you couldn't do this. There are a couple of constraints that you would want to observe. One is that you'd have to keep the tools very hot, pretty close to the melting point for aluminum. Otherwise they would act as a huge heat sink, and may cause all kinds of unintended problems, such as voids and blockages. That's not a deal breaker. It just means you'll be working in a hot and potentially dangerous environment. I'm pretty sure that steel tools would pay for themselves many times over delicate clay molds, though Another is the aluminum, itself. I believe its molded shape can distort wildly, once it cools. There may be ways to offset that. You might just allow for it. Most casted metal parts are machined in areas where precision is critical. As far as machining the tools, I would love to see someone slice a computer model into sections spaced .125" apart (in this case, mold cavity of the part itself), take those sections over to a laser cutter, cut as many sheets of .125" thick steel, stack them up, grind the cavity smooth, and go to friggin' town. I bet you it would be much less expensive than having a big old chunk of steel machined for the same part. Heck, there are things you could do with that, which relate to casting, that you simply could not do with a CNC mill. Talk to me.
Inspiracy (author)  Scrupulous7 years ago
That 1/8" laser cutting is a good idea. It is true that it's best to heat the mold before pouring. Part defects would be kept to a minimum that way. This is a powerful but very dangerous process. It would be a good idea to familiarize yourself with foundry techniques before attempting anything on this order. But if it's done right, large scale production becomes a much simpler prospect. I'll research the laser cutting process and find out how much cheaper it could be.
ewilhelm7 years ago
You can cast aluminum using sand casting techniques. Mix some heavy oil into sand and form it around a wooden, plastic, or whatever mold. I once made a solid aluminum handgun this way. Search for aluminum sand casting and I'm sure you'll find all sorts of information.
Inspiracy (author)  ewilhelm7 years ago
Sandcasting is the most common way to mold metals. The permanent mold idea is one for simple mass production. Also, the surface finish is better this way, and you don't have to build a new mold for every piece, just fill, wait, empty and repeat.
Trans_Am7 years ago
Could you go a cheaper route and try and weld/drill/bend yourself a form? That would be pure DIY awesome.
Inspiracy (author)  Trans_Am7 years ago
Yes you could bend a couple of forms with wich to mold the aluminum. I hadn't thought of that. Interesting.
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