.5" HDPE

[Bobby_B]

Anyone out there have any experience cutting .5" HDPE Plastics? I am looking for some help in selecting the Spindle Speed and Feed Rate.

[Bob]

Anyone out there have any experience cutting .5" HDPE Plastics? I am looking for some help in selecting the Spindle Speed and Feed Rate.

Bobby,
I've had a little experience with HDPE. This is a relay box I just completed:

Box

What do you plan to make?
Bob

[Bob]

Bobby,
Also, this enclosure:

I like working with HDPE.
Bob

[Bobby_B]

I am making a mounting system for some power supplies. My issue is i have to cut some pockets in the .5" material that are .375" deep and 2.6" x 3" rectangular. That cut is taking almost 4 hours because it has to do 12 of these. I am trying to figure out the settings i should use for cutting it. I am using a 1/8" Single Flute Straight Bit. currently i am using a Spindle Speed of 12000, Feed Rate of 50.0 and Plunge Rate of 15. I had cut those down because i wasn't getting smooth cuts at the default of 100 for Feed Rate and 30 for Plunge Rate. I tried adjusting the Feed rate to 75 the other day and that made the cuts fast but wasn't a very clean cut. And the machine seemed to struggle with it. I may be stuck at 4 hours I am just trying to see if there is something i am missing. Maybe a better bit or a setting i am doing wrong.

[Bob]

Bobby,
I should have thought of this sooner...Contact the Shark manufacturer, NWA. Tim Owens should be able to answer any of your questions about machining plastic with a Shark.
Bob

[Consultingwoodworker]

4 hours for that pocket size is wildly excessive, even with a 1/8" bit.

I have found a 40 ipm cut rate is good with the bit spinning at 22000 or so.

Your step over might be set too low, it should be 40% of the bit diameter. Your cut depth with the 1/8" bit should be about 1/8" as well.

Why not use a 1/4" bit to waste the material and if needed you can clean up with the 1/8? Two programs but a lot less time. Just use the same X and Y for both programs, you should only re-set the Z when you change bits.

Ralph

[Bobby_B]

Thanks Guys,

I hadn't tried a Speed over 12,000 yet since that was the default speed for the bits in the software. i will try bumping that up a bit. I am still learning. I have only had the machine a couple months and i don't use it everyday.

I do have a question for you Consultingwoodworker. You mentioned a 40 ipm cut rate and i am using 50 so wouldn't that slow it down more? Or will the Spindle speed being so much higher change that? My step over is 40%. I was considering changing the Pass depth to .188 instead of .125 so it would do do the pocket in 2 passes instead of 3.

Maybe i will adjust those values and try one pocket on some scrap plastic.

[Bobby_B]

Also i did consider using a .25" bit for the pocket then clean it up with the .125 bit. I may give that a shot as well.

[BillK]

I've cut clearance pockets in HDPE with my Bosch Colt on the Shark with a 1/2 straight Freud bit then a final cut with a 1/8 bit. That is a time saver for sure.

[milo30]

I like the 1/8" bit as I get better quality out of it but I just finished a project that took 4 hours and that was with the 1/4" bit. I'd run the pocket and check large area clearance tool then use a 1/4" or even larger. From my experience, I'd run the tool path once to rough it out, leaving it just shy of the final depth required and then set my starting depth to the new pocket and run one pass to finish it off and clean it up. My project took 4 hours because I ran everything this way, basically cutting the item twice. The time that it saved me in sanding work was worth every minute.