McMaster has the same material plus PVC. Any will do but I would go for
Acetal (Delrin) for the strength and UV resistance. For any of them the
tooling should have a positive rake and plenty of relief. The bit
should also be polished as well as possible. Plastics don't disburse
heat as well as metals so you don't want anything draging on the
surface. Turning and drilling are done at about 600 fpm and feed about
..010 to .015. Depth of cut can be pretty heavy but I don't get as good
a finish with fine cuts so plan your last pass carefully to take off at
least .02". Keep in mind that plastics expand a lot more than metal
when they heat up and deflect more under pressure of the bit. The two
factors combined make getting high tolerances right tricky. Mill to a
few thou over size and let it cool before measuring. Then take the last
couple of passes.
When it is cutting correctly acetal does not produce chips. It makes
one long ribbon that piles up on the bit and the part. You have to keep
pulling it away or it will snag on the bit and cause a rough spot.
For Delrin AF and nylons, increase the speed to about 700 fps and cut
back the feed to .007 max.
Boedeker has a pretty good page on machining plastics
http://www.boedeker.com/fabtip.htm
Geoffrey W. Schultz wrote:
I have a KISS wind generator that develops vibration at certain wind
speeds. The problem is that there's a PVC fitting that goes over a 2"
stainless schedule 40 support pipe that is loose fitting. I want to
machine one with a sleeve bearing on a lathe and make it out of plastic.
However, I really don't have any experience machining plastic, I've been
looking at www.mscdirect.com under Raw Materials/Plastic Material/Rods for
3" material. To keep costs under control I'm looking at the following:
Nylon
Acetal
UHMW
LDPE
HDPE
Comments on the machining qualities, UV resistance, and overall strength of
these would be greatly appreciated.
-- Geoff
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at:
http://www.rutuonline.com
Shameless Commercial Division:
http://www.spade-anchor-us.com