we had problems with the Y-axis dropping a few mm every time after the servo started
give error message 410 SERVO ALARM: n-TH AXIS -EXCESS ERROR
411 SERVO ALARM: n-TH AXIS -EXCESS ERROR
we thought the encoder was brokken and contacted Fanuc to check the encoder and servo
unfortunately they found no problem and said it could be a mechanical deffect (encoder was replaced for testing)
We checked everything but found nothing wrong.
even without the spindle the servo gave the same error
what we did notice was that the servo corrected with the positioning error instead of against the error
4 weeks later we chose to have a new engine brought to test and it worked
Hopefully Fanuc will let us know what specifically was wrong with the servo
PS sorry for possible spelling mistakes english is not my native language