Chatter in corners

[capmkrk]

I'm finish machining a 1/4 Radius in an ID of a 6061 Alum part that has been roughed with a 3/4 EM. The total depth of the pocket is 2 1/2 inches. I typically have a chatter problem with deep pockets of this sort. I am using a 1/4 dia Harvey Tool Long Reach relieved shank 3 Flute EM. the RPM is 1650, the speed is 10 ipm, the depth of cut is .025. Can anyone recommend an approach they use to deal with deep pockets such as this sans chatter? The geometry I am driving the tool with is a .127 rad.
Thanks

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[metalmayhem]

For that size of tool I'd say circular ramp the corners , leave .005 for finish then conventional mill at depth with a spring pass or 2 , if it still chatters then cut the depth in half .
if it's a 1/4 rad then you'd be better off with a 3/8 end mill

[machinehop5]

Three flute EM's in 90 degree corners tend to chatter. Try 2 or 4 Flute and use the EM to drill/bore out the meat of the corner .005-.010" away from finish walls/corners.. Brand New EM's can also chatter easily.

[capmkrk]

OK thanks for the feedback I will consider a 2 flute EM next time. I tried a conventional tool path and still got chatter. I use MasterCam for programming, maybe I'll try a helix bore approach leaving .005 and then a conventional finish. Drilling the corners on this part was not really feasible since the depth was 2 1/2 Inches. I could not use a 3/8 EM because the corner rad is 1/4.

[CL_MotoTech]

If you are cutting a 1/4" radius with a 1/4" end mill it will chatter. You should reduce your end mill size by a step or two.

[Superman]

OK thanks for the feedback I will consider a 2 flute EM next time. I tried a conventional tool path and still got chatter. I use MasterCam for programming, maybe I'll try a helix bore approach leaving .005 and then a conventional finish. Drilling the corners on this part was not really feasible since the depth was 2 1/2 Inches. I could not use a 3/8 EM because the corner rad is 1/4.

Use Mastercam's "Clean Corners" strategy to take the material being left to say 0.001" before doing the finish passes... this stops the finishing cutter having more than a 50% engagement within the corner

[maxspongebob]

I am with CL_MotoTech. Increase the radius slightly or use a smaller diameter endmill. It doesn't have to be much, just enough so that the endmill isn't cutting using such a large surface area. You might also try roughing with a smaller endmill so there is not so much material in the corner on the finish pass. 3 flutes is fine, my preference is the YG-1 Alu-Power.

[maxspongebob]

Your biggest problem is the length of the tool vs. the diameter. Long thin cutters are easy to make resonate. Also, have you tried regular milling instead of climb milling for the finish pass?

Also, here is a good article for your problem. https://www.haascnc.com/service/trou...eshooting.html

[Jon66]

What most people look for in a hot wire cutter is a long-range cut. The simplest way to cut (well besides snipping it off) is to extend the wire by, well, extending it. I want to prevent my wire from ripping so I come up with a method of cutting a straight line along the wire. Simply heat up a wire and slide a wire cutter along the wire (two different sizes on each side) until you hear it snap. However, is a tricky fiber and it is often difficult to pick up the best hot wire cutter for foam. When you are snipping, i.e. very close to the hot wire you can tap the wire and repeat to push the wire cut into a thinner section.

[metalmayhem]

If that YG-1 is too short, then maybe this. Your biggest problem is the length of the tool vs. the diameter. Long thin cutters are easy to make resonate. Also, have you tried regular milling instead of climb milling for the finish pass?


https://www.amazon.com/Kodiak-Cuttin...D6ZF1B1TASHKBT

Also, here is a good article for your problem. https://www.haascnc.com/service/trou...eshooting.html

the 1/4" diameter tool is 1/2 size of the radius being cut

[maxspongebob]

Dooaah. I was thinking diameter...

[metalmayhem]

OK thanks for the feedback I will consider a 2 flute EM next time. I tried a conventional tool path and still got chatter. I use MasterCam for programming, maybe I'll try a helix bore approach leaving .005 and then a conventional finish. Drilling the corners on this part was not really feasible since the depth was 2 1/2 Inches. I could not use a 3/8 EM because the corner rad is 1/4.

when taking .025" depth passes was the chatter somewhat even from top to bottom or was there more at the top ?