Need Help!- Fanuc VFD A20B-6060-H008

[cha lee]

Howdy from West Tejas,

We just picked up an old Harrison VS-450 CNC. The lathe sat around for a while but supposedly ran. Much of the documentation is missing but we seem to have gathered most of the parameters.

The latest bug to figure out is with the spindle drive. When trying to cycle a M03 or M04 the spindle doesn't move. The load meter rises and after a few seconds alarm #2 ( speed deviation )occurs on the Fanuc A20B-6060-H008.

If the spindle is turned by hand the alarm does not occur and the load meter reads 0. As soon as we stop hand turning the motor the load rises and the alarm times out again.

Interestingly if a low S code is used we can hand turn the motor/spindle fast enough to get the cycle to complete.( the cycle light goes out ) We can stop hand turning the spindle and no alarm occurs.

Strangely we can now cycle M 3,4, & 5 codes and the cycle completes altho the spindle intermittently jerks and give alarm 10. ( low incoming voltage? )

Resistance checks on the motor and wiring look OK. Checking the DC power supply shows about 340 vdc with little ripple. Altho I do want to replace the old capacitors they seem to check OK with a regular meter. Incoming voltage and wiring looks good. Outgoing voltage to the motor appears to be a few volts at most.

Please allow me to invite suggestions from the forum. We have no spindle drive manual and wish I had schematics. Never having messed around with a VFD I also wonder how the load meter works on this system.

charlie