Aluminum cut was good, now bad, any advice?

(Moncriet Montoyn) #1

Hi, I’m cutting an aluminum part from 6061, .063" sheet. I did several test pieces to dial in speeds/feeds/DOC, and once I got everything sorted out the results were excellent. I am cutting mostly with a 1/8" flat endmill, it’s the carbide 3d #102. I ended up doing almost exactly what was recommended in the wiki – rough passes .3mm DOC, dewalt speed 1.5, 700mm/min feed, finish passes were .5mm DOC, dewalt speed 1.5, 700mm/min feed.

I need to make a bunch of these, so my next step was to make an assembly in Fusion 360 of several pieces to use a whole sheet. Cutting parameters were all the same. The results were pretty bad, I had a lot of material pulled up at the edges forming a very large burr, and the cut edges are pretty gnarly:

The only set up change was switching from double-sided tape to masking tape/CA glue. I made that change both for removal/clean up ease and because the double-sided tape seemed to compress a tiny bit at times. I can’t imagine that would be the cause of this, if anything it was much more solid, but I guess I can’t rule it out. Thought I’d see if anyone had thoughts before trying again and eating another piece of stock. Any advice would be very much appreciated!

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(Idan) #2

Perhaps the bit is dull? Does it look the same with a different one?

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(Luke) #3

When milling holes in aluminium you need to use a slower feed rate - because you are going over a much smaller surface area there is allot less moment which increases heat build up - this can lead to rougher cuts and the results you see.

I’d reduce your feed rate to 500mm a min and drop router speed to 1

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(William Adams) #4

Usually this happens because your feed is too slow, and your speed too fast — the heat of the cut isn’t being carried away, and the aluminum is galling on the endmill. Things to try:

  • adjust feeds and speeds
  • use a coated endmill
  • verify that the alloy is one which isn’t gummy
  • consider coolant
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(mikep) #5

Check the endmill under magnification - it’s likely gummed up or has a broken edge. The other recommendations here about feed and speed are right on as well.

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(Moncriet Montoyn) #6

Thanks for the ideas everyone. I ordered some of the zrn coated endmills, and I’ll start over with feeds and speeds while I wait for them. Hopefully will have good results to report back soon.

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(Moncriet Montoyn) #7

For the sake of anyone like me who uses these threads for research, I’ll report my findings here. I never achieved quite as perfect a cut in as short a time as the first several pieces; probably there were a number of good luck factors involved there.

I did however, find a recipe that is consistently pretty good for me for thin (.063") 6061 T6:

  • 1/8" 2 flute Zrn coated cutter (carbide3d #102Z). From what I can tell the coating doesn’t make a ton of difference in cut results, but they seem more forgiving about slightly imperfect cutting parameters.
  • 762mm/min feed, Dewalt at 1, .3mm - .5mm DOC
  • Avoid slots at all costs!
  • WD40 is required for me, sadly. Maybe this means I don’t have stuff dialed in exactly right. I hate this, it’s a mess and means watching like a hawk the whole time, but for now I can live with it.
  • Workholding is both critical and difficult with stock this thin. For my part, the choices are either use tape, or spend tons of extra time doing holes a couple at a time and moving bolts/clamps. The good news is that the Zrn cutters seem to be slippery enough that tape doesn’t stick if you happen to contact it.

Here’s a pic of results with this formula. I’m pretty satisfied with it. Note the obvious tool marks on the edge; these get additional processing so I’m not spending time on finishing passes.

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(system) closed #8

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