Fanuc 6t alarm 410/411

[pquerro]

Help! I have a Hitachi 3NE-300 with a Fanuc 6T control. It stopped mid cycle with an x axis 410 servo alarm. I powered the machine off/on and if I try to jog the x axis via handwheel I get a 411 alarm, joystick gives the 410 alarm. I pulled the cover of the x motor mount and it does not appear to be attempting to move the motor. Ballscrew turns easily by hand. Drive gone bad?? Something simple to check??

[Al_The_Man]

Check the brushes, also it may be carbon build up causing a ground fault.
Al.

[pquerro]

I pulled the brushes. They are about 3/4" long. There was some carbon build up, I cleaned it up - still got the same alarms

[Al_The_Man]

You can test the drive by disconnecting the motor armature and turn the HW slowly on the lowest resolution, you will go so far and get a following error because the motor is not turning, but if you do not get the other alarms it probably means the motor is grounded, usually carbon track to ground, you have to megger the motor to test it.
BTW, re-HW test, if you see by the display how far it shows before you go into following error, you can turn the HW just short of that and then turn the BS by the required amount of turns to simulate the motor turning, you can continue to do this for some distance, this tests the encoder, and the drive to some extent, if you can follow what I mean.
Al.

[pquerro]

I played around with the handwheel this morning and just as you described I was able to jog a certain distance until it errored out. So if I turn the BS by hand and it sees the encoder you think the motor has gone to ground?

[Al_The_Man]

Turning it the same distance as the display, fools the control that the motor is turning, you have to know how many turns/inch to enable the BS to track your HW turns.
If you can do this accurately, turn HW so far,then BS, and so on in turn, this checks the encoder, turn the BS the right way.
The best way to check the motor is with a HV megger. Carbon track usually shows up at high voltage, your meter may not detect it.
Al.

[pquerro]

Does this typically damage the motor or is it a situation that it needs to be taken apart - cleaned - reassembled? Thanks Al

[Al_The_Man]

If it is carbon tracking, it needs to be stripped and checked for track marks etc and completely washed out with non-residue spirits.
Al.

[pquerro]

Well, we got it cleaned up. Back together and still got the same alarms. I put 12V (battery) to the motor and it runs.

[Al_The_Man]

I would try the motor disconnect test as I mentioned this not only checks the encoder, but to some extent, the drive, as it turns on the power devices.
Also you could try moving the INPX,INPZ par70,71 up somewhat to see if it removes the error.
Or STPEX,STPEZ P74,75
If you have a hard copy of the Parameters, check if they jive with the machine.
Al.

[pquerro]

We did the motor disconnect routine and it worked fine. We used the HW to jog in small increments and turned the BS by hand. We were able to "move" the axis that way without errors.

[Al_The_Man]

I would say that your encoder is OK and quite possibly 85% chance your drive is also, you could also stick a 120 or 240v lamp across the drive output when you do the test to give it a bit of a load, you should see it varying the brightness.
If you do not have a megger you need some way of measuring motor armature leads to ground using high voltage with the motor disconnected, in a pinch I have used a low wattage lamp from one lead to case on an insulated bench.
You need to be carefull if you use this method.
Al.