cutting acrylic

[badboys cnc]

I am carving signs in acrylic and lighting them up with edge lighting. I am now getting into larger sign that are about 3' x3.5'. I am using a engraver pit with a .005 tip. I'm running at 18000 rpm. and feed rate is .375 a second and .010 deep. This leaves little flakes. When I clean the sign with windex sometimes it drages these little pieces out and scratch the surface. If I make the first cut .005 and the second cut .oo8 it is better. I then blow the letters out with my air gun. Any ideas on how to get a smoother cut. Maybe speeds & feeds? Thanks Richard

[dmidkiff]

I have no experience with acrylic, but 18000 rpm seems high to me and .375 a second seems slow. There could also be a chance that a different bit would give better results. It can't hurt to experiment with different speeds and feeds and maybe someone with some experience will chime in.

[bleeth]

The type of Acrylic is also important. Cast Acrylic cuts much cleaner and smoother than extruded.
Are you cutting through the peel ply or removing it first?

[badboys cnc]

both, with paper on and off. With paper on I can clean letters with no scratches. Easier with paper off. Now I'm leaving it on.

[jerry_stanek]

Use a little water mixed with dish soap. It cools it a little so it doesn't remelt back

[badboys cnc]

Great idea. Will try. Thanks much.

[RossMosh]

I would look into adjusting your feed and rpm. It does seem like you're either spinning too fast or moving too slowly. I'd also strongly recommend that you stop using Windex. It's not the right cleaner for acrylic. Soapy water will be a much better choice. Otherwise there are specific acrylic cleaners available.

[Xray]

General rule of thumb when using rotary bits on acrylic is slow RPM's and fast feed as possible, this reduces friction and hence heat buildup.

Could try a drag bit too, it doesn't spin so there is no heat build up at all.

[gundog]

I would start by contacting the manufacturer of the tooling and ask what the recommended speed and feed or chip load is for that bit and if it is designed for the purpose you are using it.

Mike

[badboys cnc]

The dish soap and water worked GREAT. I also slowed the speed down to 14000 RPM. When everything is cut I blow all over with air gun. Very happy. Many thanks.