Problem- Fanuc Spindle Drive Vibration

[Mickey__D]

I am having a problem with my 2004 Sharp SV2412 VMC spindle motor. This machine has the 0iMateBM control with the Beta series motors. Back in November the spindle motor lost a bearing (loud whine and some vibration). During this it damaged the encoder on the top of the motor. A new motor was not available from Fanuc, so I shipped it off to Tennessee Industrial (fanucworld.com) for repair. They replaced the bearings and encoder and $975 later I am running again. It was not quite as smooth as new, but I chalked that up to new belts. Fast forward about 500 hours of spindle time and the whole machine is now buzzing at anything over 6000RPM and surface finish has gone to hell. I pulled the belts and motor side pulley and ran the motor naked and I have vibration. Also checked the current draw and it was pulling 8.2amps on all three legs going to the motor at 8k RPM measured with a clamp on meter. I called Tennessee and they said ship it back and they would check it out. I spoke with their motor shop this morning and and they said that they ran it overnight and it was smooth with no bad behavior and asked if I could ship the amp in so that they could try them as a pair in case it was a problem there. I do have an upper spindle bearing issue (next on the list), but that was isolated out from this vibration problem. Anyone have any thoughts on this? Were there any settings I should have changed when the encoder was replaced? I am about to pull my hair out!

[underthetire]

Pully out of balance/crooked ? Or the sensor is out of adjustment causing load and vibration.

[Mickey__D]

The pulley being out of balance was the first thing that I thought about so I removed it and just ran the motor naked bolted down on it's mount. The motor man over at TIE that I spoke with today did mention that the sensor had "drifted" a little out of position and they re-aligned it. Can the sensor cause this to happen?

[underthetire]

Sensor- yes without a shadow of a doubt.