Suitable cutters for ply/ chipboard etc

Hi, I have a good quality solid CNC router mill. When I try to cut thick ply or cabinet board etc using a 2 flute endmill, the cutter gets terribly hot. For example at the moment, cutting pieces from 18mm thick ply sheeting - it cuts very easily but the cutter is smoking after a cut that takes a minute or so. I have tried various sized cutters and different stepdowns per cut. At the moment I'm using a 4mm endmill and 9mm depth per cut, feedrate around 3000mm/min and 16000rpm. It's throwing chips nicely, not creating much dust, and the cut is quite sharp and smooth.

Being a narrow deep slot it's hard for the heat to get out so I've tried vacuuming the dust out of the slot by hand during the cut (the main vacuum head isn't powerful enough to pull the dust up out of the slot). And now I'm using a jet of air from the compressor directed to the tip, to both blow out the chips and cool the cutter. But it's still hot enough to burn chips at the end of the cut.

The way I've normally dealt with this is to use smaller stepdowns and do a double width cut each stepdown, to create a wide slot. But this takes a lot more time. I can't understand how the cabinetmaker workshops do it - they seem to be able to cut through 16mm dense laminated board in one fast cut. What sort of cutters do they use?

Any tips greatly appreciated! Thanks,
Andrew vB

Couple things going on here.

You're feedrate is way too low. I'd double it, but I wouldn't try to cut so deep in one pass. With bits smaller than 6mm, I don't like to cut much deeper than the tool diameter with each pass.

The burning is from all the chips packed in the cut. You'll never get the chips out of the slot with a 4mm bit. Even with a 6mm bit, you'll have a difficult time getting the chips out.

Quote:

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I can't understand how the cabinetmaker workshops do it - they seem to be able to cut through 16mm dense laminated board in one fast cut. What sort of cutters do they use?

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10mm or 12mm compression bits.
One pass, 16,000 rpm, and 15,000-20,000 mm/min. 10HP or bigger spindles
This requires a lot more machine than you have, though.

OK that helps a lot, thanks Gerry. I did get more success this afternoon increasing the feedrate and reducing spindle RPM. In future I'll stick with 6mm or bigger, and keep the plunge depth a bit less than diameter.

I'd like to chase up some spiral compression cutters too.

Funny story, I have just moved house and the CNC machine has been moved up to our new house in the country. I only got it working yesterday and set to making a new mailbox as a first project. But I found that all my collets are back at the old house and I won't be there for a couple of days. The collet that's sitting in the spindle is 4mm so that's all I could work with!! Hence the overheating 4mm cutters!

Cheers and thanks and all the best, I hope things are going well with you!
Regards,
Andrew