I am going to try cutting 3/4" cast acrylic. It is expensive material, so any advice on speeds and feeds would be welcome. I have had reasonable results cutting 1/4" acrylic, but have yet to figure out how to drill with the CNC without getting a big glob of melted plastic stuck to the bit.
You want a single flute tool — there are a couple of videos on cast acrylic at:
and I’ve had quite good success w/ such tooling using the Carbide Create defaults for “Hard Plastic”:
and I’ve also used the settings for ball-nosed tooling successfully.
I never tried to drill 3/4 acrylic.
I would peck drill with full retract and maybe a dwell at the top to let it cool.
Air assist might help.
Or drill a smaller hole then circle mill the final diameter.
What size hole ?
I imagine a drill vs helical interpolation would also lead to different surface finish on the inner walls of the hole.
Jim is probably correct, full retract with a short dwell seems appropriate.
Getting those chips out of the hole seems like the best idea, air assist would be good.
If you don’t have air assist and only need a few holes, it might be worth trying to flood the holes with some soapy water. Anything to help keep those chips from melting.
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