FANUC 3TD SPINDLE NOT RUNNING

[JMECKES]

Need some assistance. We have an old Mori with a Fanuc 3T Model D control.
At power up the spindle would not come up to the speed we set for the morning warm-up. Tried running a program in both memory and MDI, still no luck. We get about 200 rpm max in either hi or low range and it runs up to that speed very slowly. Any suggestions on where to start the exploratory surgery? We checked all fuses, but no voltages as of yet on the board.

[cncdiag]

What is the part number on the spindle drive?

[JMECKES]

A20B-0009-053 and the I/O is A20B-0008-0630

[rajesh_1355]

Is this a AC Spindle with pulse coder feedback.

[JMECKES]

Yes it is. And it started to work now. We're starting to think that after the electrics warmed up that thermal expansion may have provided contact in a broken line somewhere. We are now letting the machine cool back down to see if we can repeat the problem.
By the way, a call to Fanuc proved to be very frustrating. The tech told me that if there was no Fanuc alarm displayed, there was no Fanuc problem, and that it must be bad belts on the spindle. Nice response. My guess is that if there is any voltage at all coming in on these older controllers that the diagnostics would not set an alarm state. Funny that the control didn't alarm when the voltage wasn't reached compared to what was commanded.

[cncdiag]

Did you check the command voltage when the machine was malfunctioning?
If the command voltage is low you will not get an alarm the drive will just run slow.
It will also give an speed arrival signal back to the control.

[rajesh_1355]

Next time if it repeats, write me , I have also faced this type of problem earlier.