[jstransky]

Can somebody help me with advice how to machine soft PUR foam. Something like prototyping for automotive headrests, backrests and cushions STO foam. The only thing I now is that high RPM have to be used, up to 60.000.

[CarbonKevin]

Very high spindle RPM's, and very shallow passes. I'd be using vacuum to hold the sheet in place.

Might be worth attempting to freeze the material as well?

I've never done anything like this before, these are just my best guesses.

[brunog]

What I have seen in the bedding industry is large CNC bandsaws, reciprocating knife or abrasive wire machines. Freezing + milling would probably work on viscoelastic foam (memory foam) because it becomes hard as wood when frozen.
Best regards

Bruno

[RomanLini]

I've worked soft foams with grinding techniques, using hand tool anyway (Dremel). You need high tool speed and very low force (so you don't deflect the foam).

You can use those tool bits that are covered in diamond dust, or use the little Dremel grindstones that have a 1/8" shank.

And the dust can be nasty!

[kardang]

I know a lot about milling in foam, and I have developed the technology that we use in the company i work in. The biggest problem i fixuring, because vacuum does not work. (the foam leaks, at least the most common foam CMHR).

Dust is a serious issue. Actually the milling is not so hard, it is the fixturing and the dust collection that is the difficult thing. Also, the hazardiousness of the dust will depend on the dust grain profile. If the resulting dust is looking like oblong fibres in a microscope, you should be extra super-careful about collecting all of it and filtering the air, try to avoid generating obling fibres. An air tight, ventilated enclosure is very important, and it should have lower internal pressure than the outside (workshop) so that you are sure to filter everything. This is not metal dust, it will stay airborne for a long time. And you cannot see the dangerous dust, it is too small. Please be careful about dust collection, get it right the first time.

As for tool, use one with many flutes, sharp and run at at least 15 000 RPM.