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View Full Version : Machining Polycarbonate (lexan)?



dalesvp
08-17-2010, 10:56 AM
Has anyone turned or milled polycarbonate? I get the idea this plastic, being so tough, will not want to cut, peel or chip in any reasonable way. Perhaps some of the parts can be made of acrylic which is softer and not as tough?

Mad Scientist
08-17-2010, 11:03 AM
It is easy to cut, but like acrylic it will chip and crack if you're not careful.

Evan
08-17-2010, 11:23 AM
It machines like a dream. Use low rpm and very high feed rate with big depth of cut. Use a 2 flute cutter only. The idea is to not recut the surface as that produces friction and melting. Also use lots of air to blow away chips and keep the bit cool. The air isn't optional, especially with smaller HSS cutters.

See my video here. I have turned off the air and slowed down the cut for the video. I also use new carbide Garr cutters as they are very sharp and don't heat up the same as HSS.

http://ixian.ca/video/lexancnc.wmv

I have never had a problem with chipping or cracking.

Ack. Corrected the link, Thanks Keith.

RKW
08-17-2010, 11:29 AM
Evan,

Here is the corrected link for your site: http://ixian.ca/video/lexancnc.wmv

Keith



It machines like a dream. Use low rpm and very high feed rate with big depth of cut. Use a 2 flute cutter only. The idea is to not recut the surface as that produces friction and melting. Also use lots of air to blow away chips and keep the bit cool. The air isn't optional, especially with smaller HSS cutters.

See my video here. I have turned off the air and slowed down the cut for the video. I also use new carbide Garr cutters as they are very sharp and don't heat up the same as HSS.

http://ixian.ca/videos/lexancnc.wmv

I have never had a problem with chipping or cracking.

form_change
08-17-2010, 05:42 PM
From the workshop I used to work in there are two key points - as Evan says, keep it cool. Once the plastic gets warm it softens and dimensions can vary. Plain water is fine for this.
The other one with PC is that it can stress crack when exposed to certain hydrocarbons (even loctite will do it in), so keep your tools free from these - tapping compounds and oil based lubricants are not necessarily good things in this case. Try a piece if you are not sure.

Michael

Herm Williams
08-17-2010, 05:58 PM
I use wood router bits, less filling of the gullets. fast feed, air to keep the chips from gumming up the cut.
re

dalesvp
08-17-2010, 06:51 PM
These pointers give me some ideas about working PC, thanks. When I get 'er done I'll post some photos.

strokersix
08-17-2010, 06:55 PM
Vacuum nozzle next to the cutter makes less of a mess than air blast.

Nice sharp tools and keep it cool and you'll be fine.

Evan
08-17-2010, 08:18 PM
A vacuum is a good idea but only along with air to cool the cutter and work. I turned off the air in the video so I wouldn't get swarf in the camera.


The other one with PC is that it can stress crack when exposed to certain hydrocarbons (even loctite will do it in), so keep your tools free from these

Absolutely. Polycarbonate is very sensitive to attack by most solvents and hydrocarbons. It should only ever be cleaned with soapy water or ethanol. Not methanol or isopropyl alcohol, only ethanol. Vodka is a handy source. If the shatter and impact resistance properties of PC are important to a project it should never be glued, only fastened.

demerrill
08-17-2010, 11:10 PM
I once watched an engineering manager receive a complex machined polycarbonate prototype fresh from the modelmaker. It had a bit of dirt on it so he took a solvent dampened rag to it and was shocked as dozens of cracks instantly formed and propagated throughout the expensive prototype before his eyes.

David Merrill

beanbag
08-19-2010, 02:08 AM
I've seen people achieve good results using Simple Green (diluted) as a cutting fluid.