Cutting HDPE

[Ken Sully]

I started cutting letters out of .25 HDPE with no problems. After many letters my 1/8 inch down cut end mill bit broke. I figured maybe it just got dull, so installed a new bit and only got another 8 to 10 cut and bit broke again.
Speed 10,000
Feed 2.0 inches/second
Plunge 1.0
Making cut in 2 passes
Any ideas?

[garyb]

Where's the tool breaking at? I would check your collet
Gary

[Ken Sully]

In the center of the bit on the spiral

[chuckster]

Do you have material wrapping around the bit? I would use an upcut spiral, keep an eye on it, but if some wrapping occurs, blow with compressed air.

[Brady Watson]

After many letters my 1/8 inch down cut end mill bit broke.

Speed 10,000
Feed 2.0 inches/second
Plunge 1.0


Single flute spiral-O @ 1.2 IPS & 15,000 RPM. Not sure how many flutes your tool has, but if it isn't designed for plastic, there probably isn't enough chip clearance. The bit is most likely breaking because the chipload is too high. Turn that RPM up...and make sure you are throwing off a good chip. Even a regular 2-flute end mill (upcut by definition) would perform better than a downcut in HDPE.

-B

[garyb]

the break point of the tool suggest as Brady already noted your feed and speed are incorrect for a single flute tool.
your chipload should run around .004
Gary

[twelchPTM]

i cut alot of HDPE and I always use an up-spiral (There are no fibers to worry about fraying and its a non-porus material so vacuum holds like a champ.)

A down spiral bit will pack the cut line with chips especialy with a .125 cutter so even if your feeds are right you are adding resistance by using the down-cutter.

HDPE cuts like butter I have run .125 cutters at .125dpp at speeds up to 2ips. Not the best quality cut at that speed but it can be done.

also as mentioned above, be wary of plastic wrapping around the bit, I have a mounted air nozzle aimed at the top of the bits flutes whenever I work with plastic for that reason.