Melting ABS with small end mill

Hi all, I am having trouble cutting 1/8" ABS with a small end mill (1/16" TiN coated carbide square end mill). I normally cut ABS we a feed rate of about 1300 mm but because this 1/16" end mill is so tiny I lowered the feed to 1000 mm in hopes of not snapping it. To my surprise the ABS started clumping on the end mill even before it was done cutting the first hole. I tried lowering the RPM on a Dewalt 611 from 2 to 1 (18k to 16.5k) in hopes of lowering the temperature on the end mill but it didnt change anything.

I then started thinking maybe I had some wonky ABS and threw on a 1/8" end mill (from the shapeoko shop) and ran the same program to see if it had the same problem but this end mill cut through the material like butter with no issues.

The next difference is that the 1/16" end mill is a 3 flute vs the 18" end mill which is a 2 flute. Maybe it needs to go even slower to try to cool better and get chips out of the way. Any direction on what I should try next?

To summarize:
1/16" 3 flute square end mill, Feed 1000mm, RPM 16.5k, 1mm depth per pass, melts ABS
1/8" 2 flute square end mill, Feed 1000mm, RPM 16.5k, 1mm depth per pass, does not melt ABS

For plastics you want a suitable chipload to generate chips of a size to carry away enough heat to keep things from melting — 2 flute at most, single flute would be better.

Some information and links:

Thanks for the information, makes sense. After playing with the feeds a bit I discovered that it’s that initial drill to depth that is killing me. The milling after to make the hole the correct diameter ~1mm depth at a time is fine but going from 0 to 3.2mm at once just clogs the end mill. Do you think if I delete the initial plunge this could work? or would that put too much stress on the end mill?

Too much stress unless you can start from the outside of the stock and work your way in — alternately, do a ramp entry rather than plunge.

If it’s only the initial plunge that’s the problem, do peck drilling — drill a bit, pull out to clear chips and allow endmill to cool off, drill a bit deeper, repeat.

OK, got rid of the initial plunge to depth and instead added a tiny plunge to the desired depth on that pass followed by a pull out to clear the chips. However those chips are sticky, a lot less than before but they still cling to the end mill. I think I am just going to drill these holes by hand and order a 1 flute end mill for next time as I am running out of time to continue experimenting. Its a bit tough to make these changes using meshcam :frowning: .

BTW for any one looking to edit gcode, Sublime Text is great.
Especially the find all function that allows you to edit multiple lines at once. Just make sure your search term is bulletproof.