Introduction: Lost Foam Casting- a Basic Walk Through

Picture of Lost Foam Casting- a Basic Walk Through

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!


waacko jacko (author)2015-07-26

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

curvy77 (author)2011-12-05

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.

pyrogreasemonkey (author)curvy772011-12-25

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

EldonS (author)pyrogreasemonkey2015-07-23

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)

curvy77 (author)pyrogreasemonkey2012-01-01

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.

tinstructable (author)curvy772012-01-15

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 has a low melting point. i used to make lead fishing weights with a spoon, pliars and a fireplace.

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.

curvy77 (author)pyrogreasemonkey2012-01-17

haha so iv found out. after i use my pit forge i always end up cleaning up a ton of ash.

knoxarama (author)2013-07-08

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?

quader4 (author)knoxarama2015-05-14

Yep. Right on the nose.

RangerJ (author)2013-02-21

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

th30be (author)2012-05-28

You used a hack saw? What kind of blade did you use?

ktow (author)th30be2012-08-21

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.

theoldguy (author)2012-04-03

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.

cryophile (author)2011-11-10

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.)

ktow (author)cryophile2011-11-10

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.

CrazyClever (author)2011-11-03

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?

ktow (author)CrazyClever2011-11-10

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?

Tupulov (author)2011-10-18

Well done! Can you make branding irons with this?

ktow (author)Tupulov2011-10-18

I've thought about that. It would depend on how much heat the aluminum would hold and how hot you got it. Steak brands- throw them on the grill?

I'd considered suggesting it to students- however, I'm afraid I'd have a kid lift up his shirt after the week end and say "Dude- check out what I made in class!" Somehow this seems inevitable- so brands have been delayed.

Could be very fun.

Tupulov (author)ktow2011-11-04

Heh-heh-heh. I hadn't thought of that but I could see students diong their own version of a Jackass stunt with a branding iron. Yeah, you'd probably have to confiscate the branding irons after they were finished.

Yeah, I think this could work as a branding iron for wood. Aluminum would certainly hold enough heat to scorch wood without worring about it melting.

Keep up the good work!

mattthomas992003 (author)ktow2011-11-04

I could see a student doing that!

pfred2 (author)2011-10-23

That is pretty ironic to caption a picture of someone pouring over a concrete floor with "Pour safely." I get a kick out of it :)

ktow (author)pfred22011-10-23

Thanks for the note. While we try to keep things on the mold and in the tin cans, that's a good note on casting on concrete. I've never been so unfortunate in the hundreds of castings I've seen- however- reading stories online- it would only take one.

I've heard of folks casting on beds of sand. Any other suggestions? Obviously, you're better off not having any spill!! :)

pfred2 (author)ktow2011-10-23

Sand bed is the accepted practice. I think most that spill onto concrete regret it for one reason or another. Ferrous metals are much worse though.

msmith94 (author)2011-10-20

Pretty sure that the longhorn logo is already a branding iron at UT :) Nice video Kevin!

Uncle Kudzu (author)2011-10-19

Nice job on the video. Very instructive! I recently had someone who'd been working with iron try to explain this casting technique to me. Your video makes it very clear. Thanks for sharing!

Matt Carl (author)2011-10-19

wow so cool! Wish I could take a metals class in my high school!

mikeasaurus (author)2011-10-16

Great video of the process, and that KHPT is very neat.

About This Instructable




Bio: 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 ... More »
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