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Lost PLA Metal Casting Furnace

by 3DTOPO Feb 28, 2013
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Hi just wanted to double check but you said you used 1 and a half bags on this is that right so 1 55 lb bag and another half?

Should be crazy when the Defense Distributed crowd gets a hold of this. Still, pretty awesome stuff.

As with all new technology it can be used for both peace and war.

Wow, Thank you very much for sharing this! The instructions seem very strait forward!

Actually I don't think an electric furnace is any more dangerous than building and using a gas fired furnace, it just depends on ones ability/skills and safety precautions. I have built both, used them for many years. Just offered this as an alternative to the suburbian life stile. Anyway here is a link on how to build an electric furnace.


Good point about some places not allowing gas fired furnaces. I think electric can be more dangerous because of the high voltages and currents involved. Propane can be dangerous too of course, but it really just involves basic plumbing.

Very cool. Will you share your source(s) of refractory? I think one of these will be firing in my backyard this summer...

Thanks chowderhead! Sounds awesome!

I have been purchasing all my refractory for years from this eBay vendor: http://bit.ly/12eKqV1http://bit.ly/12eKqV1. They sell both insulating and hard (non-insulating) 3000F refractory.

If I recall correctly I used insulating: http://bit.ly/146lU3P


Here is their non-insulating: http://bit.ly/Y8YQk1


And here is the ceramic blanket I used: http://bit.ly/ZF2IcIhttp://bit.ly/ZF2IcI

I neglected to mention this elsewhere, but after the furnace has been fired out the first time, I strongly recommend applying a coat of ITC-100. It will make the furnace vastly more efficient, and protects the refractory with a zirconium-oxide (e.g. diamond) layer.

Also, http://www.budgetcastingsupply.com/http://www.budgetcastingsupply... is a good source for the refractory, crucible, tongs, fire gloves, etc.

On the furnace, you can use a home built electric furnace instead of a gas fired one, this will give you much better control over the temperature. Google Dave Gingery, little Bertha electric furnace. Here is a video link of me casting print beds with a gas fired furnace. https://www.youtube.com/watch?v=S_18UHdlfM4https://www.youtube.com/watch?...
Thank you for posting this, surely is thinking outside the box.

Hi Jeff, thanks! For this application there is no need for the greater control of an electric furnace. Electric furnaces are generally less efficient, slower to heat up, more expensive (and potentially dangerous to build) and the heating coils have a limited life. If we were say annealing glass and had to keep it at 800F +/-5F for 8 hours then definitely we would want to go with electric.

Thanks for sharing this-- I was wondering if this could be done! I am especially intrigued by projects like this to cross-over 3D printing with completely different hobbies/ interests.

Thanks Agger! To me it is the same interest hobby as 3D printing - I just don't have a metal 3D printer. yet

I've talked about this the other day on another Thing entry, it's awesome that you've came along and posted this! Nice parts by the way!

Thanks GeoDelGonzo!

first, thanks for a really interesting instruct-able/thing
I used to do lost wax jewelry and am looking to use 3d printing as a vehicle
to get designs to metal myself.
on your web you mentioned blowing out ashes,
was there much ash to be blown out?
what was the burn out times? (ramp up , sustain, drop down) (I am
assuming more traditional lost wax burn out as a reference.)
ABS or PLA burn-out residue is a concern (porosity from ash would suck!)

Also I would like to get more info about the 150 watt tube (source, cost, electronics)
I am very interested in making a laser cutter of a decent power level.
Thanks again for a really thought provoking posting!

Thank you cerberus333. The PLA burns out very clean. The first cast I did and did not blow out the ash I did end up with some minor defects in the cast.

After the plaster/sand cures up for a couple of hours I start up my furnace at about medium heat (~800F) and insert the molds. Then over about an hour I ramp it up to around 1200F. When I see that the center of the mold (looking in the sprue or riser hole) has a dull red glow it is time to remove the mold, blow out the ash and bury the molds in the sand for casting.

I bought the laser and power supply from http://www.lightobject.comhttp://www.lightobject.com

I am finishing building a multi-purpose machine for the laser that has a 5x9 foot bed with about 4 feet of Z. That is what the castings shown here are for.

Love the idea of doing this. Unfortunately I can't see suburbia really taking to me firing up the furnace :)

Pfff, I fire up my furnace all the time, neighbors just assume I'm not all there.

Your getting great results with your castings! I'll have to try your method next time.

Thanks for the link.

Touche! Thanks FreeRider!

Thanks! The Suburbs is where I had my first furnace as a kid (thanks dad!). If operated correctly it is safe and legal as a Barbeque.