Cutting technique for mdf eps acrylic sandwich

[bthoron]

I'm considering cutting some letters out of a "sandwich" of 1/4" Acrylic mirror, 3" EPS foam and 1/4" mdf. I believe that I should bond it all together and cut it from the back side (mdf first, then the foam, then the acrylic). Is this a smart idea? What are the concerns about using such a long cutting tool? Which cutter would be best for the three materials? I'll be using a vacuum table for hold down.

Thanks

Ben

[cutitout]

a compression style bit may be a good idea -- I have used one on SIP panels (OSB-EPS-OSB) sandwich.

Another idea is use some indexing pins and flip the material and cut from both sides.
Drill through the "sandwich" in locations that will not be in tool path or in part and use a peg to line up after flip. Remember to flip the tool path

The EPS is not the issue but the material on the bottom of the sandwich will cause deflection on the bit -- this is why I like to flip and cut 2 sides.

[beacon14]

Flipping the workpiece sounds like a good idea. 3 1/2" is too long to expect good quality at any workable speed.