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What is the best RPM & feed rate for cutting pink insulating foam?

1) You can blast through the material at just about any speed you'd like due to it's softness, porosity, etc. I would usually run a 3"long, .5" ball nosed bit at 10 IPS with an Alpha, and I got great detail.(I think I could have gone faster, but didn't see the need to).

Your major limitation for getting crisp detail will be the method you use to hold the foam down with. Since I was running larger pieces ( 5 feet long, and 3"deep) I chose to use drywall screws with washers on them, but on smaller jobs a Fein vacuum worked just as well. I ran both PC router and Colombo spindle close to 10,000 RPM and got a clean (for foam) finish with no burning or tear out. You can find more options and info in the holddown methods section.

2) My success with extruded styrene foam (up to 2 inches thick) is with a 1/4" CED 2-1/8" CEL spiral up solid carbide at 1.7"/sec. (max) and 16 000-17 000 RPM at a single pass cut. Anything out of those spec. as given me less than desirable edge quality. I can cut it way faster but with very torn out edges.

3) When I cut very small letters in 1 inch thick I use a 4 flute cutter instead of a 2 flute at 18 000 RPM and 1.7"/sec. for good edge quality.

How do I reduce the amount of foam that sticks to my ShopBot after cutting?

Try a box of "Bounce" anti static laundry sheets. They help to prevent static buildup as your machine is cutting, and this means you/your machine won't wind up wearing a lot of pink fuzzy foam dust around the neighborhood. The Bounce sheets also work very well for wiping down the gantry after cutting foam for a long period of time. Rubbing the surface of the foam with a dryer sheet will help reduce static cling. StaticGuard spray works for a few minutes but doesn't last. Keep a keen eye out for the foam flying in the air and sticking to your gear rack on the Y axis (foam & gear racks have a strange affinity for one another) since build-up in the teeth of the rack can cause positional loss as the pinion runs over large chunks of foam mashed into the rack...

I've found spray anti-static cling stuff works well. It doesn't last but for 5 or 10 minutes but a quick spray and vac will get the foam dust off.

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