Machining Foam

[nova290]

Does anyone here machine foam. I haven't tried, and I was wondering, what you make, what you use for foam, your supplier, and cost of the foam VS woods. Machining instead of wire cutting foam is a curiosity I want to explore. I have a project that could be cut from foam or wood. 12" x 12" x 1/2" Stock

[perryjackson]

I am cutting low-relief sculptures (e.g. coat of arms) on Dow StyroSpan foam, the least expensive kind you can find at the hardware store. It is only sold in Canada, but I tried another inexpensive brand with the same results.

The first thing you will notice is that it cuts quietly (compared to wood or MDF)! It is also easy on the machine and your carbide tools will last forever. 1/8" 2- or 4-flutes ball nose at 15,000 RPM and 100 ipm works for me. Climb machining rather than conventional prevents provides a better finish. Hence it is faster to do a spiral cut rather than a parallel one since it cuts continuously.

I just received some PreciseBits 1/16" and 1/32" Shank Tapered Ball-Nose Carving tools and I will try to carve foam with those soon.

You can cut as deep as the length of cut of the tool, say 1", in one pass with no problem. So, it is cutting faster than wood or other materials.

Dust? It comes out as tiny shreds of foam and will hold statically to the machine parts but is vacuumed off easily. I believe it is less harmful than sawdust for the machine as well, but time will tell. My machine is totally enclosed and the shoe vac is doing a fair job, but I wear a respirator when opening the box and cleaning it up (I then run an HEPA air filter for an hour in the shop).

The price is less than $20 for a 1 " thick 2' X 8'. It also comes in 1 1/2" and 2" thick. I glue it on a slightly larger 1/2" MDF for rigidity and ease of setting up.

If you needed to seal the foam (to make a silicon mold, for example), use Krylon H2O spray paint. It is specially formulated for foam and the finish is as smooth as you want.

One word of caution: once I was cutting a little more deep than the 1" length of cut (LOC) of the 1/8" ball nose. I thought that the excess foam would simply be blown away ... but no: it melted and built up like glass on the tool, destroying the part and making a mess. See the picture.

It never happened to me before while cutting within the LOC of the tool, but one cannot discard the possibility of it happening anyways, so don't wander away too far from your machine while cutting!

Cheers

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[nova290]

Thanks for the info. Guess I'll have to find a US brand foam. Do you have any photos of your foam work? I would like to see closeup pics of the final tool path.