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Thread: Fanuc 400 Servo Alarm?
05-17-2013, 08:41 AM #1
Fanuc 400 Servo Alarm?
Got a 400 servo alarm on a Fanuc 6M. This is a servo overload alarm. First one was yesterday when the machine had a part finished and was waiting for me to load another one. So just sitting, for some reason the alarm came up.
I checked all the breakers/thermal resets. All looked good. After a bit of playing around turning the control off/on a few times the alarm was gone.
Probably about 6 hours later, right in the middle of a cut the same alarm came up. And its not going away now!
The 400 alarm is for servo overload-doesn't seem to be the case here, axes are all lubed, taking light cuts, and no trips of the breakers. The servo amps all have the green ready light on. None of the alarm LED's are lit on any of the amps.
The maintenance manual suggests the connection between the drives and the motherboard may be bad. I have an identical machine, so I took the cable off of it, and still the same problem. However I did not try the 4th cable...it would be a huge job to swap that out...so I am thinking I need to test it...
Also tried swapping out the motherboards with my good running machine and still no good. The amps had some grease/dirt on them, but not bad, but I cleaned them all up. Still no good.
On the diagnostics screen, parm. 707, is saying an overload alarm is detected on one of the amps. But again, does not make sense since there are no tripped breakers or alarms on the amps.
Sooo...what I need to do is to test to see which drives are showing the OVL alarm...maybe it wouldn't show up on the amp board as an alarm? What I am not sure is how to test the cable, drive connector. I believe I am looking for 24volts on the OVL contacts if the drive is okay...not sure which pins...I think its 3? Where do I put the other lead of my meter on, to any ground?
Thanks so much for any help!
05-17-2013, 08:59 AM #2
Have you checked the motor brushes and blew the carbon dust out?
05-17-2013, 09:39 AM #3
I know on the other one I have, but this one I can't quite remember-but wouldn't there be, if there was an actual overload condition, some alarm on the drives or the breakers would trip? The drives can't be engaged-as soon as the control is turned on the 400 alarm is there...the alarm has to be cleared first before the servos can be engaged...I think the 6M thinks there is a thermal overload tripped but that I think is false since there is actually none tripped, hence my question about checking the wiring.
05-18-2013, 01:46 PM #4
Back up and running! Turns out the thermal trip reset works best with a screw driver.
Does anyone know how the adjustable dial on the thermal trip works? The one axis that was tripped has a 20M motor on it. According to the manual the trip is supposed to be set on 18. This drive its turned past it. Does it take longer for it to trip if its turned past? One would think, but 18 in the highest mark on the scale-not sure if it starts going back down once you pass 18?
05-18-2013, 11:09 PM #5
We had this a few years back on my machine, we tested all the amplifiers and cables. In that time the x axis motor had cooled enough to run the machine. Happened again a few hours later, pulled the covers off and all the paint on the motor housing had peeled off due to the heat and you could have fried an egg on it. Fixed the problem by replacing the axis motor haven't had an issue since.