Cutting Foam

I mainly want to use the CNC machine to cut foam and I was wondering if the community had any tips. If you have any suggestions on what drill bits to use, what speed the rotation should be set to, or even what kind of foam is easiest to cut I would love the input. Any advice at all is appreciated.

Have you seen this?

Details on the foam would help for sure. But for thinner foam I love djk4linux’s needle cutter. I even did an instructable on my success (and failures) building one:

But that’s only if you’re looking to do 2D cutouts of relatively thin foam. If that’s what you’re looking to do then I’d say the needle cutter is probably the best option. Almost no kerf, does tight inside and outside bends great, gives a very clean cut, almost no dust created, and no undercutting. Cutting with a spindle/bit gives a much larger kerf and is limited in how much detail it can do by the size of the bit, plus it’s usually louder and foam dust is REALLY messy.

If you’re looking to cut higher density dark craft foam then the $100 laser setup may be a good option. It’s quicker than the needle and leaves a nice “cauterized” edge - need good ventilation though as the fumes are pretty gnarly. I haven’t tried cutting light colored foam yet (I have some white on hand) but don’t expect it to work as well since light colored materials tend to reflect the laser light more. To cut foamboard like from dollar tree the laser doesn’t really work well, due to being white it doesn’t absorb enough energy and the laser diffuses through it. You can kind of melt your way through slowly in a couple of passes - but it doesn’t result in a good cut and causes a lot of undercutting.

If you’re looking to contour/engrave 3D relief inot thicker foam then just about any bit in a spindle will go thruogh it like a hot knife in butter. I use cheap 1/8" 2 flute and 1 flute bits from drillman1 on ebay and they work great.

Attached are samples of cutting dollar tree foam board with the needle cutter and black craft foam with the laser.