I milled some HDPE plate/sheet yesterday and was quite impressed at how easily it milled. At my 1500rpm max, I found that 5 ipm left a slightly frayed edge, but that went away at 10 ipm. 15 ipm was very clean as well. All of these at 0.05" doc, with a 1/8" EM btw.

So how would I do a 0.2" doc slow finishing pass with this? I expect I'd get the fraying if I ran slower.

Was it a new tool or had it already done some milling on metal?

With a new tool you should not get any fraying at any feed.

The endmill was used previously for acrylic, but it's relatively new still. I have a couple new ones that I can try/compare.

HDPE dosen't fray in my experience. UHMW does...it's easy to confuse them since virgin UHMW looks alot like HDPE.

You could probably take the entire .2" on a single pass with an 1/8" end mill unless it puts too much lifting stress on the work piece.


I usually leave between .01 and .02" for a finishing pass. 100ipm@4000rpm. Leaves a nice smooth surface.

Paul

This is definitely HDPE -- at least, that's what I purchased from McMaster. But strangely enough, I've been reading the horror stories of painting HDPE, and I seemed to have no problem with regular spray paint, no primer, but a bit of sanding. I doubt it'd durable, but I don't need it to be as this is an aesthetic part.

On my mill I've found (for aluminum) that because of my 1500rpm limitation, a nice slow 1 ipm pass taking 10-thou off gives a nice finish. And I'm anologizing for HDPE. I'll experiment a bit more.