AB Servo Sits Idle over Weekend, Won't Start Back Up (But No Alarms/Faults)

[jon05]

Hello! We are using a ControlLogix 1756-L72 PLC with two identical servo motors running separate conveyor belts. The machine this is on runs nearly 24/5 and then sits idle (but powered on) over the weekends. The last couple of Mondays, one of the servos would not start running again when starting the conveyors back up. The servo is an AB MPL-A1530U-EJ72AA using a Kinetix 350 drive (2097-V31PR2-LM). While it was in this state, I logged on to the PLC and viewed the Axis Properties and there were no faults/alarms present. We are using a "Motion Axis Jog" command to run the servo. The requested position is updating and the requested velocity is correct, but the actual position is not moving and the actual velocity is 0. The standstill bit is on as well. I tried to do a Motion Servo Off / Motion Servo On as well as a Motion Axis Fault Reset, but nothing seemed to work and no faults/alarms were popping up. The second identical servo will run normally. The only way to get the first servo working properly is to do a full power down / power up of the machine, then it starts right up like nothing was wrong. Nothing is showing up on the Kinetix drive either and all lights are normal. Any ideas as to what is causing this / ideas of things to check next time this occurs? Thanks for your help!!!

 

[baref00t25]

We recently had a similar issue with a system, but it was using Kinetix 5500 servos. We eventually traced it down to a networking issue. We ran an ethernet cable directly from the main switch to the drive and that solved the issue.

 

[DarrylR]

That almost sounds like the STO function. If the drive lost STO power over the two days it may require a power cycle to reset.

 

[mike3475]

i have that kind of issues with Kinetix300/350 all the time, no fault showing up at PLC program and at HIM of the drive. what we do is that unplug +24V on the servo drive, wait about 1 minute, then plug it in, that will reset the servo drive.

 

[jon05]

Thanks for the feedback everyone! I'm going to try to look at these options and see if any of them resolve the issue the next time it pops up.