Suggestions Need tips on cutting half inch foamcore with CNC

[USA Signs and Graphics]

My shop has a large order where we need to cut lettering and shapes out of half inch thick foamcore. The cuts are coming out very rough.

Any tips to make this go better (types of bit, spindle and/or cut speed, tricks, etc.) would be much appreciated!

 

[Inks]

Drag knife, sharp blades, changed regularly on large runs. Once dull they tend to rip out the foam.

 

[johnnysigns]

There's also the Donek knife you can put into a spindle if you don't have a dedicated knife cutter on that CNC. Toolstoday.com should have them and which variation to get on 1/2" thickness.

 

[Maxz3241]

I only used an Oscillating knife for 1" Foam, What CNC do you have?

 

[Elwood "Woody" Smith]

Oscillation knife for sure!

 

[Evan Gillette]

I have had varying success cutting foam core on our cnc router, the donek knife is on my list to try but I haven't ordered one yet. What I have found is that each brand and thickness behaves a little differently. I have just used regular O flute upcut bits that I had on hand but one of the manufacturers recommends a compression bit. A few things that are key to getting a decent cut are:
1. a sharp bit
2. feeds and speeds are very finicky, lots of testing to get dialed in
3. use a bit diameter the same or greater than the material thickness
4. test cut direction (climb vs conventional) to see what cuts better.
5. Material makes a bit difference. Cheap foam board is miserable. Maybe consider gatorplast or something like palboard, the increased cost will likely be offset by the hassle of dealing with bad cuts.

 

[Modern Ink Signs]

Oscillating knife…..