Hello,
I have an Okuma lathe with 6TA control, Fanuc DC servos, and Fanuc drives. The servo motors have 2000ppr encoders built into them. Here is the problem:
I get a 410 alarm on the X axis. (value of X error register exceeds limit when axis is stopped.)
Watching diagnostic 800, I can watch this error develop. After powering up in the morning and zero returning, DGN 800 will read about 0003 or 0004, with a little flutter, perhaps 1 or 2 counts. Throughout the day, the value slowly goes lower- for instance to -0015, -0020. This continues till it gets to -0150 or so and then the machine faults.
I pulled the X motor off, trued up the com, had the armature tested, cleaned everything, and put it back together. Problem is better, but only slightly. Also, i tried lifting the axis with a length of wood between the tailstock and the cross slide. The negative number gets bigger doing that; apparently negative is up.
So why is my motor drifting up? And strangely, the parts I'm making are still holding tolerance just fine. The problem seems to only affect the axis at rest. But it will fault while moving if the error gets big enough.
Z axis is fine.
I tried enabling the auto-drift compensation feature in parameters. Didn't help any.
Also, this machine does not have a counterbalance for the X slide. It does have a brake, but the brake is only active when power to the servo is off. I checked that it works properly and does not drag. In case it matters, the X ways appear to be receiving plenty of lube as well.
Any ideas?
Thanks!
Kevin
I have an Okuma lathe with 6TA control, Fanuc DC servos, and Fanuc drives. The servo motors have 2000ppr encoders built into them. Here is the problem:
I get a 410 alarm on the X axis. (value of X error register exceeds limit when axis is stopped.)
Watching diagnostic 800, I can watch this error develop. After powering up in the morning and zero returning, DGN 800 will read about 0003 or 0004, with a little flutter, perhaps 1 or 2 counts. Throughout the day, the value slowly goes lower- for instance to -0015, -0020. This continues till it gets to -0150 or so and then the machine faults.
I pulled the X motor off, trued up the com, had the armature tested, cleaned everything, and put it back together. Problem is better, but only slightly. Also, i tried lifting the axis with a length of wood between the tailstock and the cross slide. The negative number gets bigger doing that; apparently negative is up.
So why is my motor drifting up? And strangely, the parts I'm making are still holding tolerance just fine. The problem seems to only affect the axis at rest. But it will fault while moving if the error gets big enough.
Z axis is fine.
I tried enabling the auto-drift compensation feature in parameters. Didn't help any.
Also, this machine does not have a counterbalance for the X slide. It does have a brake, but the brake is only active when power to the servo is off. I checked that it works properly and does not drag. In case it matters, the X ways appear to be receiving plenty of lube as well.
Any ideas?
Thanks!
Kevin