[botha.y]

Hi guys,

Still knocking my head for overlooking a reset button on an overload for three hours while troubleshooting another machine.

Anyways here's what I have, dunno if someone could help. It's a Pegard Precivit Milling machine with a Fanuc 15M control. The spindle is a alpha60HV (A06B-0883-B100/3000), with a spindle amp A06B-6104-H275#H520, Power supply A06B-6091-H175 and Capacitor module A06B-6083-H245.

Now here's the issue: after running the spindle for a couple hours at 100% at high speed the spindle starts going at about 60% of the speed it should be going and the speed is very unstable, rapidly changing +/- 50 rpm. If I go to 50% override or below speed is always stable. It does the same thing for any speed except 100rpm and below. Spindle goes up to 3000rpm with 4 gear stages (motor goes up to 4500rpm). If I leave the machine to full rest and no power for a few hours, the problem goes away and comes back after a couple of hours of machining. Does anyone has any clue what could be the issue here (I say very likely spindle amplifier, so if you know what should be repaired on it?).

I tried to lower the velocity gain (proportional and integral) just to see what it would do it allowed me to go about 10% faster at a stable speed but that was all.

Thanks.

[underthetire]

Id scope the spindle motor sensor, sounds like the motor may be getting warm changing the sine wave off the sensor.

[Jade York]

I would start with checking the speed sensor amplitude before and during speed fluctuation. You should have a nice clean sine wave for the A & B pulses and the amplitude will stay constant. I have seen spindles run anywhere in range from 290mV P-P to 640mV P-P. The pulse width should also stay constant. Let me know if you have further questions.

Sincerely,

Jade York
888-740-9016
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