I am trying to figure out how to machine HDPE. The problem I keep running into is that the plastic gathers at the top of the cutter when I do plunging or drilling and then when it goes into future holes it melts and ater several holes cause marks in the top of the plastic I am machining. I am OK when I do linear movements but the plung causes the spirals of plastic to stay on the cutter.

Here is some tests I did tonight.

g01 Z.5 f25 with my router set to 1 spindle speed cause lots of small plastic piece to gather up on the cutter.
g01 Z.5 F50 does the same thing only the parts are better.
g01 Z.5 F120 gives me real nice plastic spirals but still bunches up at the top of the cutter.

Here is the cutter I am using tonight.. I have used a few similar cutters but they all do about the same thing.

http://www.leevalley.com/wood/page.a...168,46171&ap=1