Post By metron9
Machining Polyethylene, especially UHMW?
I'm thinking of machining UHMW for a new shop project. I'm strictly a home shop machinist. In the past I'm not sure if I had UHMW or HDPE, but I'm looking for tips.
Machining is pretty straight forward, but I don't seem to get a very good surface finish. On the mill I'm using HSS endmills. Also the surface gets dirty after machining very easily. How do I improve surface finish and how do you keep freshly machined surfaces clean? Or do you clean the surfaces up after machining is done? If so, how...soap and water?
And while I'm here, do you find much of a difference between HDPE and UHMW?
Thanks in advance,
Make sure your endmill is nice and sharp, you can feed it as fast as you can wind the handles(or as fast as you power feed will go), spindle speed as fast as you can.
I machine alot of UHMWPE at work and it always gets dirty,soap and water cleans parts up great.
Another trick for surface finish seems to be having the milling head tilted over ever so slightly so the back of the cutter doesn't rub(of course you can only feed in one direction and get a good result)
As a general rule, use virgin endmills for plastic. If the endmill has cut even a little aluminum, the EM while still sharp, the edges are no longer dead sharp and will leave much bigger burrs on plastic and create higher cutting temps.
Originally Posted by Neshek
Most standard HSS endmills are ground to a point with no corner radius, which ends up tearing the UHMW. Stone a corner radius on the endmills (R.010" to R.030") and surface finish will drastically improve and not trap dirt in the grooves left by a zero radius endmill.
UHMW also finishes quite nicely with an old school HSS flycutter ground with a HIGH positive edge and a generous corner radius. Finish stone the edge razor smooth. Bigger radius means faster feed. Tighten up the tool good and tight and wind the RPM up.
I have found the Solid Carbide Spiral 'O' Flute bits to be the best at machining all plastics. Air and the O flute, no melting, I love these end mills.
Thanks everyone. There is nothing like talking with someone who knows. I love this site.