Cast Aluminium Gears





Introduction: Cast Aluminium Gears

This instructable will show you a technique of casting known as lost foam casting, to create aluminum gears. The gears in this instructable do not have any real purpose other than decoration, but with more time and patience, you could create gears for actual use on something. Please vote and favorite!

Step 1: Watch the Video

I made a full tutorial on creating these gears. I recommend watching it, as it goes a little faster than reading this instructable, and goes into further detail.


Step 2: Templates

For this project, I use Matthias Wandel's gear generator to make templates for my gears. The generator is made for creating wood gears but it worked just fine for my purposes. The site is very simple to use and is totally free. After I made a set of gears, I printed them out on normal printer paper and glued them with glue stick onto some flat pieces of polystyrene foam.

Step 3: Cutting Foam

After the glue is dried, I went and cut out the gears with my homemade hot-wire foam cutter (Instructable coming soon!). Make sure to follow the lines as close as you can, so the gears fit together.

Step 4: Casting

To begin the casting process, I first sifted out a bunch of dirt to a get really fine particle soil. I then mixed in some motor oil to help the soil clump together and buried the foam gears in it. I used a steel baking tin to hold the dirt in, so that if any aluminum spilled out, it wouldn't ruin the container. When I buried the foam, I held a glue stick on it and later pulled it out to act as a chimney for the liquid to flow down. Be careful to not cave in the chimney. After your mold is set, you can start the fire, I used wood as my fuel but coal or charcoal would be much better. To get the fine hot enough to melt aluminum, a fan is needed to blow on the fire to supply it with lots of oxygen. Once the fire was started, I turned on the fan and put in my crucible. The crucible is the container that hold the aluminum while it is melting. My crucible is made of the bottom of a steel propane canister, but any steel cup or container will often work. I used aluminum pop cans as the main source of aluminum. Once it was completely liquid, I carefully poured it into the mold chimneys and waited for it to cool.

Make sure while doing this, that you have all the necessary safety equipment at all times. This includes: face shield, fire proof gloves, long handled pliers/tongs and a fire extinguisher.

Step 5: Filing/Finishing

After I pulled my gears out of the mold, they looked very rough and uneven. Since these gears aren't going to be held or touched very much, I won't need to polish them as much as my Aluminium Handled Knife, but I still want them to look better than coming straight out of the molds. I first clamped the gears in the vise and cut off the bit of aluminium that filled the chimney. For the first gear, I used a normal hacksaw, but it took a very long time so for the second round, I used a Sawzall with a metal cutting blade. Then I flipped the gears in the vise and used an angle grinder to grind the faces down to a more silvery finish. After that, I used a drill to cut out the holes that had been filled in the casting process. Finally, I used an assortment of metal files to fine tune the teeth and sprockets of the gear. In the end, I could have spent a lot more time on them but I didn't have a use for them, so for now, they will stay rough.

When I cast the gears, the larger one didn't fully take shape and ended up not having several teeth. To solve this problem, I used IFixit, a kind of putty-like epoxy, and sculpted the teeth by hand. It actually turned out very well and worked better than I had hoped.



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    Well, when the molten aluminum, which is very hot, first touches the foam, the foam rapidly disintegrates and the aluminium fills the mold. You might think that the sand would cave in directly after the foam is gone but actually the fumes of the burned foam slightly harden the inside walls of the cast, and they stay firm enough for the metal to full it completely. I hope this helps a little bit, as it can be very confusing.

    I don't know pretty much anything about casting, but I want to try it. So I don't really understand how the molten aluminum takes the gears form?

    How many cans do you need to make something that size?

    4 replies

    I've cast cans into ingots and it takes quite a few cans. The main trouble with melting down cans is how thin they are. Being so thin they tend to oxidize more than they melt. Oxidized metal is not the nice shiny stuff that you're looking for. I find that submerging the cans to melt them helps out a lot, but that has its own hazards doing it too.

    The other thing to note is that cans are pure aluminum. Pure aluminum is not the best casting alloy of aluminum, it isn't an alloy at all. You can alloy your pure aluminum with some zinc and have a better material.

    If you want to add zinc to your alloy, remember that pennies are made from zinc, with a copper coating, which can be removed any number of ways. And no, its not illegal to melt pennies down for the zinc, the law about messing with money is very specific, and indicates that defacing them to change their value is illegal (making a silver dollar out of a quarter) but turning them into something that is not money is perfectly fine.

    You would have to add quite a bit of zinc to reach the ratio that Zamak is. Diecast metal is mostly zinc. I think that would be more economical material to use than pennies.

    This is exactly what I was going to post: cans are pretty cruddy to cast with. A better solution would be to go to craigslist and find an aluminum block lawnmower in the free section and haul it off. Yes, it does require a lot of work to disassemble and clean (clean material = less crap to skim), but it is a casting alloy and will be night and day in difference in your results.

    About 20-30 was enough for this project. You want to have a little more than you need just in case. Also, if you crush the cans into a small ball, they will produce more liquid.

    collect hard drives, good aluminum for use.

    I actually did poke a few vent holes but didnt bother to write about them. Sorry about that :)

    On larger items it helps to put vents to allow gas and air escape. You still sometimes end up with voids but they often help eliminate them.

    I wonder how heavy it would be they look pretty chunky

    My uncle used to cast replacement Studebaker parts like door handles from melted down pennies, but pennies were 100% copper back then. He used the lost wax process then would clean & polish them up and send them out to a plating company to have the parts nickel then chrome plated.