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I just dont get the chatter (turning chatter aluminum)

IAMATT

Stainless
Joined
Aug 3, 2009
Location
LAS VEGAS, NV
QT15 cutting aluminum 6061


Well here we are facing and boring at .130 DOC and I am getting chatter noises. I am on center with the tool tips. Spindle sounds good but its a chattering irritating and bad finish on finish bores. Tried new inserts and made sure everything is tight but I still get squeels even on a face cut that takes off .020.

Jaws seem to stay tight through the range and I am not over 2300RPM on 6" aluminum. 190 on the chuck pressure.
 
chatter

QT15 cutting aluminum 6061
Well here we are facing and boring at .130 DOC and I am getting chatter noises. I am on center with the tool tips. Spindle sounds good but its a chattering irritating and bad finish on finish bores. Tried new inserts and made sure everything is tight but I still get squeels even on a face cut that takes off .020.
Jaws seem to stay tight through the range and I am not over 2300RPM on 6" aluminum. 190 on the chuck pressure.
.
you do not mention insert type and coolant
.
a built up edge of aluminum on tool bit will hurt finish as well as too high a rpm which uses so much horsepower to cause tool bit and boring bar vibration.
.....maybe try a slower rpm, lower DOC and less radius on carbide inserts??
.......boring bar diameter and stickout from tool holder are incredibly extremely important factors in determining max DOC.
...... a larger diameter boring bar sticking less out of tool holder can do wonders at lowering chatter and vibration
 
1" CNMG stnd square holder hanging out mabye 1.5"
1.5" CNMG boring bar sticking out maybe 3.5"s

This isnt my first run here but its strange like this chatter came out of nowhere and I cannot find the issue.
 
Check to see if the turrent is fully locked in that position,try putting the tool holder in another position and see if it still chatters.
 
This post addresses many things that are not tooling or material related, that I have found to be the sources of, or contributing to, chatter or surface finish problems.

The previous posts have great points to consider first. If no relief is found, a basic "reality check" of the machine is in order.

Spindles that "sound good" can still have "play" causing chattering. Even a couple of tenths of slop in spindle bearings, or tool deflection is cause for concern.

Mount up a good .0001 indicator and check the spindle for "play" both radial and end play. Then push and pull on the turret, rotational, X and Z axis. And last, chuck up a bad part and look for slop in the chuck.

Has the chuck been recently greased?
Any recent crashes?
Has anyone tried to adjust the headstock for taper and not tightened things?
Are the belts loose? or too tight?
Any employees that may not admit oops situations to the boss?
Have the chuck and turret been off in the last year? Rust and crud inside causes problems.

Try running the spindle at 10 to 20 RPM, does it turn smoothly, or nearly stop then speed up during a turn of the spindle (there may be several of these in a single turn)? 20% speed variation is to be expected, but 50%+ is too much. The spindle drive has a power supply that gets problematic on these older machines and causes parts of the 3 phase power to the motor to to be missing, resulting in uneven rotation even at higher speeds.
On mills, this kind of problem results in dropped tools or breaking pockets in the tool magazine, but on lathes it is seldom noticed.

Hopefully it is some little thing that has not been noticed, Cause it's the little things that getcha!

Bill
 
Check to see if the turrent is fully locked in that position,try putting the tool holder in another position and see if it still chatters.

Spindles that "sound good" can still have "play" causing chattering. Even a couple of tenths of slop in spindle bearings, or tool deflection is cause for concern.

Belts and coolant mix I will also check. The rest are covered and in good shape.

:o
 
190 for chuck pressure may be a bit low for a 6" diameter part. I generally run my QT's between 250 to 300 psi chuck pressure. Only going lower for delicate work, or up around a max of 350 for tough applications.

Your part may not be seating well in your chuck jaws. If the bore of the jaws has taper, or deflects too much when clamping, the part will only be held in one small circular area, or "ring", and this can let the part wiggle a bit when being cut.

Has your material supplier slipped in some bad Chinese aluminum??

Try bumping your max rpm's down to 2000 or 1500....or even 1000. Or drop your cutting tools SFM way down. Aluminum will never know the difference for surface finish.

As far as machine problems go, the most likely scenario is problem with the turret clamping. Turret shafts have been known to crack or break, clamp piston o-rings go back and leak, the nut holding the turret to the shaft may be loose, or you may have a hydraulic pump going bad????

Good luck with it...and let us know what you figure out.

Greg
 
gib tightness

on a lathe the carriage and cross slide and compound rest usually have an adjustment for tightening the play in the slide movement.
.
i like to feel a reasonable resistance when i turn any cranks for the slides.
.
tightening the gibs on the slides usually helps with mysterious vibration.
.
some tapered gibs have an adjustment screw on opposite ends. i twisted the head off a gib adjustment screw once because at the time i was not aware of the opposing one at the other end. just a word of advice in that gib adjustment screws should not need extreme force to tightened. when in doubt read the machine manual.
.
also perform shake, rattle and roll
.
1) with a magnetic base and dial indicator grab machine parts and see how much play or movement there is in spindle, slides, tool post, etc
2) listen for rattle or mysterious noises
3) when powered off if it has no brake does it take some time to slow down
.
shake is the most important test. many machines look fine until you check for movement or play where there should be little or none
 
on a lathe the carriage and cross slide and compound rest usually have an adjustment for tightening the play in the slide movement.
.
i like to feel a reasonable resistance when i turn any cranks for the slides.
.
tightening the gibs on the slides usually helps with mysterious vibration.
.
some tapered gibs have an adjustment screw on opposite ends. i twisted the head off a gib adjustment screw once because at the time i was not aware of the opposing one at the other end. just a word of advice in that gib adjustment screws should not need extreme force to tightened. when in doubt read the machine manual.
.
also perform shake, rattle and roll
.
1) with a magnetic base and dial indicator grab machine parts and see how much play or movement there is in spindle, slides, tool post, etc
2) listen for rattle or mysterious noises
3) when powered off if it has no brake does it take some time to slow down
.
shake is the most important test. many machines look fine until you check for movement or play where there should be little or none

:smoking: LOL I think you forgot I was working on a turret CNC lathe. Thanks for your time though I do appreciate the effort. Toolcat I think your right an old employee messed with the pressure adjust on the two selenoids in the turret. I dont think she is clamping like she should be. Its most likely a $400 service call to get it right :crazy:
 








 
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