Cutting Masonite Faced Foam Board

[RossMosh]

I have the task of cutting a product. I have to cut a 2D semi complicated shape out of 1" XPS Foam(at least that's the best I can figure) with .08" Masonite faces. I'm cutting with 1 pass using 1/4" bits. RPM tested between 17,000 and 10,000

I've tried 3 bits and each have their problems:
1. Standard 2 flute Up-Cut Endmill. This resulted in two issues. The first being the edge facing up is tearing and results in a good bit of sanding. The bigger issue is the masonite is heating up the bit and as a result the foam is welding to the bit. This is translating to the foam core.

2. O Flute downcut. Left undesirable edges both on the masonite and foam.

3. O Flute upcut. Slightly better than the downcut, but only slightly.

So I'm at a bit of a loss how to handle the project. Without going into too much of an explanation, buying a bit for the job is not really an option. My only creative idea is to do the job with 3 passes. Top masonite. Foam. Bottom masonite.

[knight_toolworks]

do you ahve the Masonite up or down? down would seem good and using a upcut bit foam does not tear with a upcut and a upcut cutting the masonite would not tear either. when cutting foam you can't have any shaft touching the foam only flutes. oops I see masonite on both faces. have you tried two passes on to cut the face the second all the way through?

[twelchPTM]

you could also cut the shapes slightly larger and then cut the actual size in a single pass to clean it up. I have cut many different foams with ease using a good sharp 2 flute up cut. When I first started I went through every type of bit without even considering the standard 2 flute when nothing else worked I tried it and it was good. I also set up an airline to blow a constant steam of cool air blowing on the bit, It doesn't keep every bit of foam off the flutes but it definatly helps

[joe]

I'm with Tom on this one. By using one of the "premium" double fluted bits with a clean-up pass seems to work every time. Because I'm not a vacuum hold down person, bridges or tabs would serve.