Incoming power is fine.
I will amp clamp the incoming to see if it is being disturbed.
The speed is steady, so the electronics are compensating for what ever this is?
I do not have a multi-channel storage scope and three induction probes.
The motor over heats (80C).
The problem only happens at certain motor speeds, above and below are fine.
The problem is exactly the same hot or cold.
Horizontal boring mill, gear head. The speeds that have the disturbance will over heat the spindle motor. Fanuc has been in on the problem, and swapped out the drive, and tried to tune the problem away, with no luck. Motor meggers OK? Any ideas?
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I would be looking for a problem in the gear train between the spindle and the motor. Likely a bearing going bad or gear with a tooth chip in it or else the spindle.
Could also be the spindle brake is either toggling off for some reason. That you could see on the I/O display and or rack. Now that could be a bad wire that has an intermittent connection.
For a bearing to be bad enough to put enough drag on the motor to cause an overheat, but then get better at higher RPM doesn't seem reasonable.
It is a nightmare to get at and do, and no neutral.