Chatter Issue with a IH - Please help

[turbotoys]

I'm having a horrible chatter issue when using a 1/2 carbide End mill in 6061 aluminum. Cant seem to locate the issue. I thought maybe it was the spindle so I took it apart and checked the bearings and everything seemed fine - put it back together and adjusted the pre-load and same issue. Took it apart again and replaced the bearings with angular contact bearings. Same issue.

Depth of cut .125 - feed 11.5 @ 3000 RPM - 1" Stickout - 2 flute HTC Carbide end MIll

I have tried slowing the cut down and increasing the RPM but the resonance is still there. I have the column filled with Epoxy Granite so should have some extra stiffness.

I'm new to this hobby so maybe that is just too deep of cut but I can take a heavier cut with a 1/4" end mill. Also, when i'm done with the cut the bit is cool to the touch so its not like its forced through the stock.

Any suggestions??? I have a lot of stuff to cut out this holiday weekend and if i have to use my 1/4" bits its going to be a long weekend :-)

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[turbotoys]

No One???

[vertcnc]

I would check out some F&S calculators, such as FS wizard. I think for .125 DOC and .200 WOC you should be moving more like 35 IPM. Check your end mill for any chips in carbide. I would just use HSS tooling 2 Flute for ALUM. Cheap great results and you don't cry as hard when you make a mistake.

[turbotoys]

Thanks for the reply vertcnc - I actually use GWizard -

I forgot to mention that I am doing a pocket so when I first start the cut it does a long slot so I would have a 180 Degree contact angle on the bit and that is when it sounds the worst - obviously because i'm cutting the most material. The bits are new.

According to GWizard i should be able to take a 1"DOC & .5 WOC @ 3000 RPM and a feed of 7.5IPM with the slider set to finish. I have a feeling i would break a bit as soon as the first few teeth contacted the part...

Today I used a dial indicator to check the gibs and try to get rid of any additional slop that I may have but I am at .001 or less on all 3 axis's. I checked to make sure the column bolts were all tight and they were. I only have maybe 15 or so hours on the machine so I doubt the slop is in the ballscrews/nuts but that i will be checking next.

Just wondering what kind of speeds and feeds others can take with their IH mills on 6061 and 1/2" bit.

I am using solidcam pocket operation and there is no option to change the cut so it uses a smaller engagement angle.

[G59]

SolidCam is good cam software. what version are you using? I find it hard to believe there's no setting to change the ramp in/out angle.
Have you tried the Helix or Profile settings adjusting the ramp strategy?

How about your constant Z?

[zero_divide]

Thanks for the reply vertcnc - I actually use GWizard -

I forgot to mention that I am doing a pocket so when I first start the cut it does a long slot so I would have a 180 Degree contact angle on the bit and that is when it sounds the worst - obviously because i'm cutting the most material. The bits are new.

According to GWizard i should be able to take a 1"DOC & .5 WOC @ 3000 RPM and a feed of 7.5IPM with the slider set to finish. I have a feeling i would break a bit as soon as the first few teeth contacted the part...

Today I used a dial indicator to check the gibs and try to get rid of any additional slop that I may have but I am at .001 or less on all 3 axis's. I checked to make sure the column bolts were all tight and they were. I only have maybe 15 or so hours on the machine so I doubt the slop is in the ballscrews/nuts but that i will be checking next.

Just wondering what kind of speeds and feeds others can take with their IH mills on 6061 and 1/2" bit.

I am using solidcam pocket operation and there is no option to change the cut so it uses a smaller engagement angle.

Your problem is not so much wrong speeds and feeds (though you are going verrrrryyyy sloooowww)
Use a 3 flute endmill. it is much more stable and does not chatter even at much larger stickout.

[MichaelHenry]

And try zero_divide's FSWizard speed and feed calculator. G-Wizard can sometimes give you pretty bad data.

[arizonavideo]

I do a lot of cutting with the IH at 8 IPM and .2 DOC with no chatter if I'm not in a slot which is why I go that slow as most of the stuff I do is slots.

You don't say how your clearing chips.

I would put an indicator on the tool or better a 1/2" drill rod and apply pressure to the rod and look for slop. A loose ball screw or end bearing will show up only in one direction. If the chatter is all directions then it is the spindle or head.

Describing the chatter a bit more might help too. How deep and if it is in all direction and under what type of cut?

[turbotoys]

I do a lot of cutting with the IH at 8 IPM and .2 DOC with no chatter if I'm not in a slot which is why I go that slow as most of the stuff I do is slots.

You don't say how your clearing chips.

I would put an indicator on the tool or better a 1/2" drill rod and apply pressure to the rod and look for slop. A loose ball screw or end bearing will show up only in one direction. If the chatter is all directions then it is the spindle or head.

Describing the chatter a bit more might help too. How deep and if it is in all direction and under what type of cut?

What RPM are you running with that depth of cut? Is that a 1/2" bit you use?

I am clearing chips with air - and I'm spraying some WD40 to lubricate the end mill so the chips don't stick. Yesterday I put an indicator on the spindle and I couldn't get it to budge more than .0005. I just put new bearings on the spindle in preparation for the belt drive you will someday make me (and patiently waiting for i might add) ;-)

I will double check the ball screws today - The other day I put my hand on the table to try and figure out what was chattering and it felt like the table was solid so ill start with the upper components.

I am using a .125 cut and it seems the chatter is all directions.

[turbotoys]

I think i'm on to something.... I bought a Fowler Electronic edge finder a few weeks ago. I was going to send it back because if i spin it, it wobbles a little bit so I thought it was defective. Now it just occured to me "what if the collet is bad?" So I put in a 1/2" x 6" long end mill and measured about 1" out of the collet and I am .0035 out if i spin it by hand. if i measure it right out of the collet i'm still off by .002 I am assuming this is significant and is probably my issue? What do you guys think?

[vertcnc]

.002 Will deftly effect surface finish and could cause some chatter, but not sure you would hear it.

[turbotoys]

Hmm... I didnt want to hear that... lol Thought i was on to something....

I took my Shars ER32 Collet holder out and my runout is .0002 - as soon as I put that collet holder in it goes up to .0013 then I put a collet and bit in there and then it goes up to around .0026 depending on what collet I use. I think I would be better off not using the ER32 collet holder and buying the R8 collets that fit right in the machine. At least it might improve my surface finish.... LOL

Now if i could just fix the main issue.... Been messing with it for days... Running out of test pieces.

[vertcnc]

You could try a set screw holder. The other thing is try couple different type tools. (3FL, 2FL, HSS, Carbide) I have had really good luck with HSS especially when your limited to around 3000 rpm. You can also ajust the feed rate during cut and see if anything changes.

[Sparky_NY]

Any progress locating the source of the chatter?

[turbotoys]

Nope - I have a new complete spindle that I ordered as a spare. I have been to busy to try that one yet. I just got my belt drive conversion in and will be installing it this week and will change the spindle at the same time.

[lcvette]

Any luck tracking down the chatter issue?

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