Bridgeport 760/20 X-Axis seimens servo motor hunting/ giving vibration during run

[Harmeet]

Hi everyone...
In our bridgeport 760-20, Heidenhain 2500 B with seimens drvies, X-Axis is giving excessive vibration during runing....
When the machine is run on full feed then machine shows, GROSS POSITIONING ALARM, sometimes A, B or sometimes C.
but when feed rate is less than 50%, it X-Axis runs but with vibration from the motor...
Please help.......

[machintek]

I have seen 2 reasons for this. The hall effect triggering transistors inside the motor are misfiring. In the second case I had a defective cable that was arcing to the ground wire in the cable. In this second case the machine shook so bad in the Y axis, I thought it would start moving the machine. My meter could not find this using the ohms setting. I cut the cable open to find it. That after replacing everything else. It was a new install.

George

[Harmeet]

thanks machinetek for reply.....
I have already tried replacing the encoder cable which goes to siemens drive but hadn't replaced the Cable going to LT unit...
can you tell me which cable you are talking about...?
1. Motor encoder to Siemens drive or encoder cable to LT unit or Power cable..?
2. If in 1st case as told misfiring than motor has to be replaced?
Please reply...