Cutting HDPE faster

(Amanda ) #1

I have been machining relatively large parts out of HDPE on my Nomad 883 pro. I have been using the recommended settings for HDPE and using Mesh Cam
DOC- .02"
.125 ball cutter
Each part takes hours to complete. Are there settings I can change to speed things up a bit without sacrificing too much quality? Or should I just be more patient?

(Phil Thien) #2

You could try a test with increasing the DOC and see how the quality looks. The Shapeoko 3 calls for a DOC of .125" w/ RPM of 21.5k, feed 65 and plunge 32. I know the Nomad isn’t a Shapeoko but you could reverse the chip load from the Nomad and the Shapeoko and compare and try to get closer to what the Shapeoko is doing.

Although full disclosure: I have not machined HDPE on the Shapeoko.

(mikep) #3

If you can use a .25" cutter on your geometry, this is one of the few times that makes sense on the nomad. HDPE is so easy to cut, the bigger cutter really speeds thing up. I’d also recommend at least roughing with a square mill, the ball mill will only ever use a bit on the tip at that depth of cut, and it’ll take that much longer because the passes will be so close to each other.

(MachineHeadLabs) #4

I concur. 1/4" cutters work great on HDPE. Unlike most plastics, HDPE is self-lubricating and doesn’t melt at higher RPMs.

(Amanda ) #5

Thanks for the input! I am really a newbie using a CNC and really do not know what I am doing half the time! I have a few questions. Using a 1/4 cutter to rough it out sounds like a good idea. Some of the geometry is too small for the 1/4, however. Will MeshCam rough out what it can, then can I switch to a .125 to finish? Do I have to do some special coding or will MeshCam just figure it out? Also can someone explain what DOC, feed, and plunge means and how it effects the cut? Sorry for all the questions!

(mikep) #6

Meshcam makes it easy. It’ll have a tool change after the roughing to use the tool you specify on the right side of the toolpath generation screen for the finishing passes. It’ll rough what it can with the 1/4, which will get rid of the bulk of the material at deep DOC, and plenty fast. Then you only have to run the small bit slowly for what’s close to the geometry.

(Andrew Van Lahr) #7

Amanda, Yes, you can rough cut with the 1/4" tool, and then finish with the 1/8. This is kinda complicated to accomplish and I’m sure others with more meshcam knowledge than me could help you out. However this is essentially the same process I’m using with Carbide Create.

What I was going to suggest was possibly trying another material, specifically Komatex expanded PVC, it’s been a dream to work with for my business. Let me know if you need some help locating it. Usually calling your local plastics distributor is the best first step.

(Amanda ) #8

Just a little update. I changed the DOC from .02 to .04 and have been slowly increasing the feed rate with each project. I am now up to 120 and everything still looks fine and my Nomad doesn’t seem to mind at all. That has really cut down on the time it takes to complete the job. So far so good!

(Jerry Gray) #9

Wow! You’ve at least quadrupled your time savings!
Thanks for the updates. They are important IMO.

(Max Rothwell) #10


I’ve been using a 1.5mm flat end mill for machining very small HDPE pieces that require a fine finish. I’ve had no problems using much faster settings than you’ve suggested, albeit using half the DOC:

RPM - 6250
DOC - 0.25mm
cutting feed rate: 600mm/min
plunge rate: 60mm/min

Hope this helps!