Studio 5000 MAM instruction enabled but not initiated.

[JTPLC 0]

Hi All,

I currently have an intermittent issue on a CompactLogix 1769-L30ERM with firmware 28.11. When I get to the machine, all conditions for automatic running are true and it looks as if the machine is in sequence.

When looking in the program the next rung in the sequence is a motion axis move instructions. The conditions are true and the EN flag is true. However the move never starts its movement and the IP or DN flags never become true (pictured). I can move the servo with a motion direct command and use the position and speed of the MAM instruction and it moves as it should.

The only way I can seem to clear the issue is to drop power and reinstate.

I am under the suspicion it may be a bug in the firmware, does anyone know of this issue?
 

[BobLfoot 301]

Not Sure if you have a step 39 but I would suggest the following for Step 39

EQU Stripper_Seq.Current Step 39 XIC M2_Stripper_Servo_Instructions.MAM_Servo_Move_1.EN OTU M2_Stripper_Servo_Instructions.MAM_Servo_Move_1.EN MOV 40 Stripper_Seq.Current Step.  

It is probable that your MAM was enabled and errored but something reset the error but not the Enable.  In this case the instruction doesn't fire again.

I'd look for usage of  M2_Stripper_Servo_Instructions.MAM_Servo_Move_1.EN,  M2_Stripper_Servo_Instructions.MAM_Servo_Move_1.ER,  M2_Stripper_Servo_Instructions.MAM_Servo_Move_1.DN and  M2_Stripper_Servo_Instructions.MAM_Servo_Move_1.PC and see if there manipulated elsewhere.

[JTPLC 0]

Hi, thanks for your feedback, I have been to similar issue again and there are 3 servo drives on the equipment and it isn't always the same drive which has an instruction issue similar to the one described above. it also isn't always the same rung which gets stuck.

The latest fault was on a MAG (Gear On) instruction, when I got to the machine I could not see any fault codes etc on the drive, however there was an error code when expanding the Tag, ERR 5 which I believe means the servo loop was open. and also a safe torque off alarm was present in the drive status after clearing the log.

if anyone could take a quick look at the word document attached, and has any ideas that would be a big help.

Line 5 fault.docx

[Joe E. 259]

I've seen weird things happen when the same tag was used in multiple motion instructions. Very intermittent. It usually worked fine but would occasionally...not. And it wasn't predictable when/how/where it would fail.