[Drew]

Burgmaster Mill 6M Spindle issue
6044-H007 model 3 AC spindle
Sometimes the spindle acts up speeds up,slows down and even reverses for just an instance.
Checked feedback and found sqr wave off a little on duty cycle. 35 to 40%
Sine wave feed back looks good (.6v wave at 2.5 rms)
I have pictures and video will add when i can.
I have two servo units and have seen it on both and was wondering if it could be the motor?

[ame="http://www.youtube.com/watch?v=hU2J2V6_LYo"]Burgmaster Mill 6M[/ame]

[Drew]

Could this be caused by line voltage being 246 rms?

[Perfect Circle]

Have you checked your spindle encoder & spindle drive control?

[dlservice]

After watching that video it sure looks like a feedback issue with the encoder or cable. Have you checked all the connections on the cable ? That type of problem is not likely in the motor.
You could test the motor out of the system by applying 3 phase voltage directly to the motor and see if it runs smooth without issues. But still looks like feednack issue. Try another cable & or encoder.

[underthetire]

I've seen that once before, helping a friend. It was on a mori lathe with a 6 as well. It ended up being a built in sensor inside the spindle motor. It was a fanuc drive witha fuji motor. Cleaned, adjusted and it ran good. Ordered another sensor just in case.