Tips for Cutting Foam on a CNC or CNC Machine

One of the most interesting things I’ve done recently on a CNC machine is using it for CNC foam cutting. And by foam, I simply mean standard building foam that you can get at a home center. It’s inexpensive, and machines great. You might use it to create a finished item, or to mock up something you plan on cutting out of more expensive material later.

Router bit selection
Great news! Standard router bits work great on foam. No need to go looking for specialized cutters.

Feed and speeds
For CNC cutting foam you can run at a fast feed rate. 100 inches per minute is fine. But it’s best to lower the rpm on your spindle or router to 10,000 rpm or so. You want to make the CNC is cutting the foam, not burning (and melting) it.

Finish the foam
Want to mask the fact that this project is foam? You can paint it with latex paint, or coat it with Foam Coat. Latex paint because the solvent in other paints can melt the foam. Foam Coat is a cool product that will make it look almost like stone.