Mori Seiki MV35/40 AC spindle RPM

Hello everyone

I have been a reader to this useful forum for many years and it has helped me many times but now I have a problem. We have an old Mori Seiki MV35/40 CNC mill which has worked great for many years but after I repaired a hydraulic leak in the ATC cyclinder it developed a new problem. I noticed that the spindle would take a long time to spool up to the desired RPM and the CRT display would not register any "actual" rpm (actual RPM = 0). The spindle does rotate to the programmed RPM but it take a long time to reach the desired RPM and it has no torque behind it. When I try cutting at a heavy load the rpm drops down with no compensation to the load???

The machine will do successful tools changes and there are no problems with the X,Y, or Z axis. I do have manuals and have been trying to trace the problem; spindle encoder signal, signal conditioning, etc. Any suggestions or recommendations would be really appreciated.

You'll need to add some more information. The Mori MV35/40 was available with Fanuc or Yasnac controls. Depending on the vintage, could be an AC or DC spindle drive and motor. With out knowing this there is no place to start with suggestions.

This may not be it, but its worth a check. Pretty sure the MV35 uses the same spindle drive arrangement as an MVJR- just bigger travels. If so, the spindle is belt driven by a pair of multi groove flat belts. IF your oil leak soaked the belts, they may be slipping. Had the same issue with my machine- thought the spindle drive was failing- no torque. No one - even Mori said to check the belts. I thought the spindle was direct drive but no.
Pull the sheet metal cover off the head, and you can access the belts thru an opening in the front of the head casting. There is a tension adjustment on the spindle motor in the front at the base of the motor flange. Loosen the bolts holding the motor and slide it back and you can reach in there and take the belts out and clean or replace them. For what its worth, my 10M has never displayed actual RPM on the control. Hope that helps.