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  #1  
Old 06-06-2019, 12:47 PM
Terry Williams Terry Williams is offline
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Default UHMW Feeds and speeds help

I'm getting ready to do some work cutting some intricate parts using 54" x 96" x 1/4" HPDE sheets so I finally decided to make a pressure foot for my Cobra 510.

This is the first time I have cut UHMW and I only have one piece 12" x 12" x 3/4" so I won't be able to experiment with speeds and feeds.

I plan to use a 1/4" O-flute and an 1/8" 2-flute Ball Nose for the eased edge of the pressure foot.

The "slide" holes need to be fairly accurate since the bolts connected to the pressure foot will slide up and down to maintain the spring pressure on the foot and too much slop can cause binding while too little clearance can cause excess friction.

Can someone give me an Idea as to what the speeds and feeds and depth of cut should be for UHMW cutting parts like the attached image?

Thanks,

Terry
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File Type: jpg PressureFoot.jpg (58.0 KB, 55 views)
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Old 06-06-2019, 01:48 PM
guitarwes guitarwes is online now
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180-200ipm at 16-18k rpm conventional cut. Use a profile toolpath with inside spiral ramp for the holes. If you have a vac table use an onion skin on all parts before the cut thru pass, otherwise use tabs. I usually cut 3/4" thick material in 3 passes with a 1/4" bit (.35, .35, .06)
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Old 06-06-2019, 02:17 PM
Terry Williams Terry Williams is offline
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Thanks, That's what I was looking for.
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Old 06-25-2019, 03:22 PM
TimPa TimPa is offline
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Quote:
Originally Posted by guitarwes View Post
180-200ipm at 16-18k rpm conventional cut. Use a profile toolpath with inside spiral ramp for the holes. If you have a vac table use an onion skin on all parts before the cut thru pass, otherwise use tabs. I usually cut 3/4" thick material in 3 passes with a 1/4" bit (.35, .35, .06)
can you please tell me where the spiral option is? thanks in advance!
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Old 06-25-2019, 08:43 PM
Terry Williams Terry Williams is offline
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Sure, it's a Spiral Ramp on a Profile toolpath. See the attached image:
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Old 06-26-2019, 07:52 AM
TimPa TimPa is offline
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thanks, can't tell you how many times I looked there.... old age
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Old 06-26-2019, 10:17 AM
guitarwes guitarwes is online now
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How did the cuts do Terry?
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Old 06-26-2019, 10:21 AM
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My hope is you cut a test piece first !
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Old 06-26-2019, 11:45 AM
Terry Williams Terry Williams is offline
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I had to put the pressure foot on hold for a little while. I had some revenue producing jobs come through at the last minute that interrupted my project but I'll resume as soon as I have some idle time.

The same technique worked flawlessly on some HDPE parts I made for a recording studio desk. Clean and accurate cuts for the most part - had a little birds nest issue with the last couple of holes.

I will definitely do some test cuts in the UHMW before the final part is cut since I only have one piece of material - I haven't done much work with that stuff yet so I'm not taking any chances.
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Old 06-27-2019, 09:53 AM
guitarwes guitarwes is online now
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Quote:
Originally Posted by Terry Williams View Post
The same technique worked flawlessly on some HDPE parts I made for a recording studio desk. Clean and accurate cuts for the most part - had a little birds nest issue with the last couple of holes.

I will definitely do some test cuts in the UHMW before the final part is cut since I only have one piece of material - I haven't done much work with that stuff yet so I'm not taking any chances.
HDPE cuts almost 99% like UHMW, with the exception of the reprocessed kind. Both are considered "soft plastics". Same chipload, feeds, speeds, bits, etc. The birds nest are from drilling holes that are close to the diameter of the bit not letting the chips evacuate. That's why the inside spiral toolpath is almost a must when making small holes. A smaller bit diameter is excellent also, but there are limitations (length of cut, material thickness, etc). If you use a drilling toolpath (drilling straight down), just about every hole will produce a birds nest on your bit and "surface burnish" your material around the subsequent holes.

You probably already know this but just putting this out there for anyone who finds this thread in the future.
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