machining polyurethane

[mcmachine]

We got a job that require me to machine some polyurethane. It has to be done in the CNC mill using our 3D software. It is shore D 40. Any tips on feed and speeds and cutters would be great. I am going to have to use a ball nose for all finish passes. Thanks for any help

[Pres]

I think you can use about any feed and speed your spindle rpm will permit.
2 flute for max chip clearance is best.
Chip load 0.001" to 0.010"

Main concern will be keeping the chips cool enough so they don't pack up in the cutter.

Lottsa air and maybe some mist to keep 'em slick to eject from the cutter a bit better.

It's one of the more forgiving plastics to cut, at least @D 40.

Good luck,
pres

[mcmachine]

stock came in this week. I squared some blocks this morning. Shell mill (1.25) looks like crap. Fly cutter with HSS tool looked ok, just fuzzy. Fly cutter with carbide lathe tool looks the best. Loaded part in the mill and machines pretty good. Got two coolant hoses on it using a .375 ball three flute. 3800 RPM at 30 IPM ( fastest it will move.) Roughed out with a two flute at 20 IPM and 3200 RPM. Just has to find the sweet spot where it wouldnt chatter. Coolant is ice cold today.