Machining polycarbonate ("Lexan")

[J.R. Hatcher]

Sean I need help. I need to cut some .25 lexan, any suggestions on parameters, or suggest a clear plastic that will cut better. I will be doing some lettering and also some graphics. thanks

[smreish]

JR,
Lexan is also known as Polycarbonate for those that don't know.
I recommend a onsrud #52-624 or similar 1/4" diameter.
Cut at 15K RPM or so, 35-60ipm, 2 - 1/8" per pass.

[J.R. Hatcher]

Thanks for the info Sean, I'll give it a try.

[smreish]

...JR, a little additional information.
Get a spiral up bit, 1 or 2 flute made for soft plastic.
The real key is get the chips out of the cutting path, otherwise they weld themselves back in the kerf and make for an ugly part.
Acrylic is really known for this, Polycarbonate doesn't weld as much, but it's really soft compared to other cutting materials.

[cncb]

I would recommend cutting most plastics with an o-flute cutter. I cut this with a 1/4" o flute up spiral and as Sean says good to get rid of the chips; up spirals do just that. Leaves a really smooth finish quite minimal chatter/tool marks if any. Not lexan, but cast acrylic. I'm sure it would cut very similar.

http://joescnc.com/gallery/albums/Completed%20Work%20Pieces/vacplate-2.jpg

[cncb]

http://www.woodcraft.com/family.aspx?familyid=8017 here's the one I use, but onsrud and amana, most companies carry them

[J.R. Hatcher]

Thanks for the help guys :) Brian that's a nice cut.

[smreish]

Brian.
That is the same quality of cut I getting on my machine as well with Spiral Up Onsrud bits.
Thanks for posting a picture!

[cncb]

Np; but I def noticed a huge improvement in quality of cut in plastics when I went to the O-Flute. It just ejects chips nicer and leaves a cleaner finish. Onsrud, whatever company you use o-flute for plastics seems to be the way to go.