Lost Foam Casting- a Basic Walk Through





Introduction: Lost Foam Casting- a Basic Walk Through

About: I'm an educator in Waukee, IA. I love making stuff, learning, playing ultimate frisbee, and flying kites. I live with my 2 boys and my lovely wife Heidi.

I made this walk through of lost foam casting for my high school students in my metals course. I hope this gives you a good feel of the process!

Be safe and enjoy!



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    31 Discussions

    would i need the dry wall cover? or can i just use the styrafoam? also can i bury it in dirt or is sand needed? i have limited materials.

    8 replies

    well i think the first thing you must do is make a furnace to melt the metal. then worry about where and what to pour it into

    im a sort of safty freak so im starting with aluminum. this way i can still use my fire pit and have an open space.i have no need for a furnace yet.

    You'll need a furnace for Aluminum since the melting point is much higher than a fire pit will provide. If you watch the video, he explains that you don't need the dry wall paint, but without it you'll have a sandy texture.

    i agree with you tinstructable...however i think he should use lead...it has a low melting point. i used to make lead fishing weights with a spoon, pliars and a fireplace.

    No to lead! Tin works really well and has a much lower mp.

    actually, you can melt aluminum with a fire pit. it just wastes a lot of fuel, and you need to tend it a lot to make sure the pot is in a good hot spot. a fire pit can get to about 2k f if you blow on it. you can even melt iron with just wood and a good blower! it takes a TON of work.

    If you don't have a furnace to use, then you can just use a fire to melt aluminum as it does not take much to melt... Use wood like elm... (Thats how I melt aluminum)

    Hey I thinking of doing this for a metal replica of a paper model I've made would this still work if I switched out the foam for paper ? Guessing so just getting conformation

    So the mold isn't a hollow spot in the sand, its just that the foam mold burns away and the metal takes its place?

    1 reply

    Good Instructable, and one less reason to keep delaying getting into the casting hobby.

    Sorry on the delay- I suspect it was a 14 tooth hacksaw, but honestly, most any would work- the aluminum is exceedingly soft compared to most any other metal.

    This is a version of, "lost wax casting", where the wax is heated to empty the mould before casting.

    Sometimes frozen mercury is used, allowed to melt and poured out for reuse.

    Sometimes flowers or insects are used.

    The idea is to produce a mould for each casting. Foam is just another medium. It could be set in a latex shape then covered with plaster and dissolved with a petroleum solvent to leave the empty mould.

    It produces very intricate with low dimensional tolerances, it is used to make items like jet turbine blades at very low cost.

    Very nice! I have been wanting to make geek-themed brass belt buckles for quite some time. It seems like this method would work, but I am slightly bothered by the idea of continually having to make patterns. (I guess I could try making my own CNC mill and do it that way.)

    1 reply

    Thanks- if you're really interested in casting- greensand molding with a pattern works wonderfully- just requires a little more on the front end and forces you to consider draft angles.

    If you're not familiar- draft refers to the fact that green sand cast objects must have a slight taper to them to accommodate removal of the pattern. I.e. a pattern with a 90 degree edge fouls the impression it makes when removed. You add a slight taper (5-10 degrees- the more the easier) and it can release more easily. I've had kids make buckles before- both on CNC in foam, and in foam by hand- That's a great project!

    Let me know if you need any pointers.

    is there any limit to how big the foam sculpture can be? I was thinking using this technique for something about the size of a football,, would that still work?

    1 reply

    Sorry on the delay- Limit-wise, it would depend on your crucible. Usually our castings are no larger than about "baseball sized" for volume.

    When you get too big, I think you could have some shrinking issues. Typically students get their best finish on the bottom side with most of the shrinkage occuring on the top side of the casting. If you really want a great finish- drywall works great- or you can use paper (glued on with rubber cement) to ensure a smooth finish.

    Aluminum football perhaps? What's the project?