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Some materials are just tough to machine

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  • Some materials are just tough to machine

    Styrofoam. Thought I'd put this word first so you can skip the topic if it sounds like it's going to be stupid.

    I potentially have a project in styrofoam which will require a lot of milling to get to the shapes needed. It would seem that the minimum radius at any point would be about 1/4 inch, so I'm thinking that a 1/2 inch ball nose end mill with a high helix angle might just 'cut it'. I'll be able to hot wire most of the excess material away, but the end result needs to be smooth and machined-looking. I'll be able to control the tool path accurately, but the question is about getting a finish on it that looks like it's been sanded and ready for paint.

    Almost any router bit will cut foam, but I'm thinking that a combination of a shearing action and an uplift will leave the type of surface that's basically done, without divots and little rips everywhere. An alternative to some type of cutter would be a miniature sanding belt, going around a very small tip roller. There will be a vacuum system used regardless, as otherwise there will be so much styrodust that you would soon lose sight of the part, amongst other evil things that can happen with static charged dust clouds.

    From all the various workings with styrofoam over the years, I've learned that you need to apply as little force as possible to remove material so it doesn't tear. Even sanding it you can pull little cracks into it, but if the sanding is very light it's ok. So light pressure on a high speed sanding belt would probably do it, of course with the vacuum dust removal thing going at the same time. Sanding will basically puree the foam, so I'd rather use the alternative of a router bit, but with an optimal shape. Just wondering what that shape might be, and whether there's a suitable cutter made.

    Perhaps I could make a little hoop from some thin material and sharpen the edges, then spin that on the end of a router shank.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Try silicon bronze. Then talk to me.



    • #3
      For sanding, I would use a small diam. sanding drum in the mill spindle. For milling, I would use a single flute end mill made to cut plastic. You can get the single flute end mills in up cut or down cut.
      Kansas City area


      • #4
        You seem to be on the right track using a ball nosed milling cutter. But used in a router not a milling machine. High speed will help keep the bit cool as any serious heating of the cutter will cause all sorts of problems.