Cutting styrofoam with a CNC machine and turning it into aluminum

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.


  1. ColdTurkey says:

    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?

  2. Nippey says:

    > (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!

    • spike says:

      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.

  3. 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.

  4. 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.

  5. Bill says:

    Any sources for the ytong bricks in the US?

  6. abc says:

    You should use open cell foam

    • ar0cketman says:

      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.

  7. anyone says:

    real hack. but as others have mentioned, the casting part was not well documented.

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