Tips for Cutting Foam on a CNC or CNC Machine
George VondriskaDescription
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.
More on CNC work
If you want to know more about working with a CNC machine, WoodWorkers Guild has you covered. Getting started? You may want help making sure you understand the basics of a CNC machine. Ready to position material on your machine? Have a look at these tips for lining up your CNC machine.
I'm always looking for cool new stuff I can do on a CNC machine. And one of the things I've been messing with lately is cutting styrofoam. So yes, this pink stuff is not jello. This is building foam from a home center, two inches thick. We'll talk about some of the advantages why this is cool, but lemme get going on a cut here. I've set up to do a 3D fish out of this foam. I've got a quarter inch router bit in the machine right now that's gonna rough it out. Then we'll change to a quarter inch ball nose. That's going to finish it so you can see just what foam cutting looks like. It's pretty cool stuff. The roughing pass is done. Bonus points if you can tell what this shape will be when it's all done. Roughing pass was done with a quarter inch up cut spiral cutter. I am running the bit at about 10,000 RPM. When you're cutting styrofoam we want to make sure the bit has the opportunity to cut, it doesn't start to burn. So 10,000 RPM is pretty good. My feed rate is just under a hundred inches per minute. So we're cutting pretty fast on feed, but lowering the RPM. Now I'm going to use a quarter inch ball nose and that's going to finish the shape out. So let's get that cut going. Dust collection is pretty important for this, that styrofoam builds up quite a bit of static electricity. So good dust collection is going to really help confine that the shavings coming off of it around two. Here we go. Who among you guessed fish? There it is all done. Isn't that cool. Now there's some products out there that allow you to coat styrofoam so it no longer looks like styrofoam when you're done. You can also paint styrofoam but you need to make sure you paint it with a latex paint. If you use a paint that's got a stronger solvent in it, it can actually melt the styrofoam. So do a little research on that before you're going to apply paint. But I think it's so cool that you can take a product like the styrofoam, cut an object out of it and get something that when you're all done looks nothing like styrofoam. So it's a great way to prototype projects. Practice your CNC work, it really does cut like a dream. It's not that expensive. It's worth experimenting with.
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