Well...
I've got a problem with a sliding head CNC lathe, Fanuc 0T control, M series d.c. servo drive & motor.
Poor surface finish on the part & a "grumbling" axis.
Believed it to be the x-axis motor, so got it off & away to a motor shop that had done work for me in the past.
They pulled it down & the bearings weren't good, & the brush gear was heavily contaminated.
Full wash & brush up, with new bearings, ran fine, refitted seemed OK.
Drive taken back also & ran OK on test bench.
Couple of weeks later noise back again.
Discussed with client Engineer rebuild of 2nd motor, as it was same age & same use, they agreed.
Rebuilt 2nd motor.
Fault reduced.
A few days later overload alarm (shared overload).
Went to site, traced overload alarm to TM O/L on drive.
Checked overload changed setting through full range and reset to factory no more trips.
However, rough surface finish remains.
Spindle was growling, spindle motor OK, checked out spindle layshaft, rough NDE brg. rebuilt layshaft, spindle itself seems OK.
Ran machine rough surface finish, spindle quieter.
Now jogging X-Axis, this is vibrating quite badly.
Left machine powered up and not running for a few hours, motor very HOT!
Remove motor return to test bench runs fine, strip & check NDE brg. a little rough, replace & rebuild.
Align magnets with brushes as a double check even though the parts are marked, end up in same place!
Return to machine still rough in jog.
Swap X & Z axis motors, X now smooth, no vibration on Z, but, Z is now resonating when holding position.
Gut feeling is resonance is at same frequency as noise through X axis.
No drive changes to affect tuning.
Also as the motor has been moved from axis to axis, the feedback interpretation, control channel, cables, power stage etc. have all remained with the original axis & the fault has moved, thus it points to the motor, if it were a drive tuning issue I would have expected the fault to remain with the drive/axis rather than with the moved motor.
The only thing I can find is rough encoder bearings, however, the encoder pulses are all fine on a scope.
The encoder feeds direct to the CNC which outputs a speed tacho value to the drive for the drive to control the speed loop, whilst the CNC controls the position loop.
Any ideas, anyone, because I can't think of anything else!
I've got a problem with a sliding head CNC lathe, Fanuc 0T control, M series d.c. servo drive & motor.
Poor surface finish on the part & a "grumbling" axis.
Believed it to be the x-axis motor, so got it off & away to a motor shop that had done work for me in the past.
They pulled it down & the bearings weren't good, & the brush gear was heavily contaminated.
Full wash & brush up, with new bearings, ran fine, refitted seemed OK.
Drive taken back also & ran OK on test bench.
Couple of weeks later noise back again.
Discussed with client Engineer rebuild of 2nd motor, as it was same age & same use, they agreed.
Rebuilt 2nd motor.
Fault reduced.
A few days later overload alarm (shared overload).
Went to site, traced overload alarm to TM O/L on drive.
Checked overload changed setting through full range and reset to factory no more trips.
However, rough surface finish remains.
Spindle was growling, spindle motor OK, checked out spindle layshaft, rough NDE brg. rebuilt layshaft, spindle itself seems OK.
Ran machine rough surface finish, spindle quieter.
Now jogging X-Axis, this is vibrating quite badly.
Left machine powered up and not running for a few hours, motor very HOT!
Remove motor return to test bench runs fine, strip & check NDE brg. a little rough, replace & rebuild.
Align magnets with brushes as a double check even though the parts are marked, end up in same place!
Return to machine still rough in jog.
Swap X & Z axis motors, X now smooth, no vibration on Z, but, Z is now resonating when holding position.
Gut feeling is resonance is at same frequency as noise through X axis.
No drive changes to affect tuning.
Also as the motor has been moved from axis to axis, the feedback interpretation, control channel, cables, power stage etc. have all remained with the original axis & the fault has moved, thus it points to the motor, if it were a drive tuning issue I would have expected the fault to remain with the drive/axis rather than with the moved motor.
The only thing I can find is rough encoder bearings, however, the encoder pulses are all fine on a scope.
The encoder feeds direct to the CNC which outputs a speed tacho value to the drive for the drive to control the speed loop, whilst the CNC controls the position loop.
Any ideas, anyone, because I can't think of anything else!