One of the most popular ways of turning an object trapped inside the world of a computer into a real, metal object is the art of lost wax, or lost foam casting. In this process, a full-scale model of the object to be made in metal is crafted in either foam or wax, placed in a pile of sand, and burned away by molten metal.
[ptflea] over at the Bamberg, Germany hackerspace Backspace came up with a very clever build that automatically cuts foam into the desired shape, ready to be taken out to the backyard foundry. The build is based around an old flatbed scanner and a hot wire cutter. The old scanner conveniently had an equal number of steps per axis, so attaching an Adafruit motor shield and replacing the old control electronics was just an issue of finding the correct resistors.
Software control is provided by a Processing app [ptflea] whipped up and is able to carefully cut very delicate shapes that even the steadiest hand would have trouble with.
Making stuff out of styrofoam is cool and all, but the real goal for this project was setting things on fire and melting old heatsinks. The styrofoam molds were placed in a bucket full of sand, and the furnace – a few ytong bricks, a crucible, and a propane burner – started to melt some aluminum. The molten aluminum was poured onto the mold and after cooling, the makers of Backspace had a few very cool aluminum trinkets.
A nice build that is able to produce some very nice metal objects. We suspect, though, that a higher-density foam (something along the lines of blue or green insulation sheets, if they have those in Germany) could produce an even higher level of detail if you’d like to build your own.
Videos after the break.
Forgive me if this sounds dumb but I’ve not rly come across this before. How do you get from cutting foam or wax to having something that can contain molten metal?
He turns the foam INTO a metal mold by pouring the molten metal. Wathc the video.
well he probably WOULD if there was a video to watch:
“…Videos after the break.”
Nope something is not working…
(also assuming he knew what a break was – I don’t – and don’t give me a load of BS about RSS feeds or whatever)
Videos work fine for me (Firefox on Linux).
If you don’t use an RSS reader, turn “after the break” into “3 lines down”.
Seems like the hot metal is burning the foam away. http://www.hackerspace-bamberg.de/Aluminumcasting_en
A wax model is covered with something like plaster. Then the plaster and wax are heated and the wax is drained. The result is a plaster mold in which you can cast molten metal.
The styrofoam piece (core) is embedded in molding sand (=sand + additives that make it stick together). Then the liquid metal is poured into the mold via a canal; the styrofoam burns in the process.
Other techniques create a two part mold and the core is removed before the actual casting (because it is made out of a material which will not burn away like styrofoam).
Finally a wax model of your object can be covered with sand and ceramic which creates some kind of shell, the whole thing is then placed in a furnace which hardens the shell and melts the wax. The result is a hollow mold which can be filled with molten metal and can be easily broken after molding to retrieve the metal object.
It was just fine quartz sand without any additives. In fact it was so fine you can see the small balls from the styrofoam. We had a jar with the quartz sand and the styrofoam piece in it. A tip of this piece was outside so we could fill the aluminum in.
Styrofoam is 99,…% air and only a small part plastic, so it burns nearly without any debris when it makes contact with the around 700°C hot aluminium (=1292°F).
Here you can see the progress stepp by stepp:
http://www.hackerspace-bamberg.de/Aluminiumguss
or here the English URL http://www.hackerspace-bamberg.de/Aluminumcasting_en
> (something along the lines of blue or green insulation sheets, if they have those in Germany)
Yep. We have :)
Last time I was cutting foam, I used a jigsaw with a hot wire. The CNC approach is definitely cooler!
Those insulation sheets are composite materials, they have solid layers separating the foam layers, this could be a problem for the casting process. Obviously denser foam means more plastic that needs to be burnt out.
Depending on which type you use, you can also sand the denser foam boards. Could be a cool way to achieve some nice curves and smooth edges.
A safety point to consider: Put sand down over your casting workspace. If you spill aluminum on rock or concrete it spalls and hurts like a (expletive).
Great Project. Love it.
Any sources for the ytong bricks in the US?
Ytong is just a brand name, available throughout Europe. It’s simply aerated concrete ( http://en.wikipedia.org/wiki/Autoclaved_aerated_concrete ) There should be many other brands; Google gives for example http://www.aerconaac.com/ Should be available in any building supply/home improvement store.
You should use open cell foam
A few problems with open cell foams:
1) They are more expensive and difficult to obtain than polystyre.
2) As far as I know, all affordable open cell foams give off toxic fumes when cut with a hot wire.
real hack. but as others have mentioned, the casting part was not well documented.