Problems with a servo on contrologix

[crsgab 0]

Hi there: We have a winder machine working with a controllogix controller , it uses a 8 axis Sercos interfase. I'm very new using controllogix as most of PLC on the plant are SLC5 series so I"ll really thank you if you could help me with this problem. The winder has 4 servos connected ,the problem is the second servo called "jumper" when machine is wiring this servo moves down a screw transmition assembly connected to a guide, it moves when the number of turns per coil are done so it moves down 3 times , on the third movement lifts the guide to its home position, the problem is that sometimes after third movement guide remains down and doesn't go up , we don't get any error messages on sercos interfase or amplifier module neither on PLC,so we turn off the machine and manually lift the guide, this problem happens randomly, it can be working a full shift and it doesn't fail. I was reading that there is a way to send motion commands from Rslogix 5000 but as I said I'm new with controllogix and also this machine is within an enclosure and there are several pieces near servo. We have checked mechanical transmition assembly connected to servo and this is ok we don't have slips Any way to determine if servo is ok? Thanks in advance. Gabriel

[BobLfoot 302]

The Guide which needs to be lifted is lifted by which servo {1,2,3 or 4} or by a pneumatic cylinder? If I read correctly servo 2 moves the work table and after the guide lifts it moves back to "home". To send commands directly to a RS5000 Servo look in the Explorer tree and find the servo in question. Right click on it and select motion direct command. This is how you give commands. Look forward to more information.

[TimWilborne 108]

Also it would be good if you could post your program since it is an erratic problem. This could be a timing issue in the program if you are getting no faults of the servo axis or drive

[OkiePC 14]

My first suspect when dealing with A/B motion control and a machine that "gets stuck with no errors" is that the axis is still moving and not within the position lock tolerance. The I Gain for that axis is set on zero and the other gain values are too low to overcome resistances that prevent the axis from physically moving to get within the position lock tolerance. This is all just a W.A.G. but I would first look at the Axis Status of the last part of the machine that moved, or the next one that is supposed to move to determine where you are stuck. Unless the drive faults, or the ladder logic provides for a time limit for each movement, a servo axis can sit there indefinitley "pushing gently" against a load but not quite getting there. Look for an axis that has "moving" for its status, but doesn't appear to be going anywhere. Compare it's command position and its actual, and have a look at it's position lock tolerance (not to be confused with position error fault tolerance). If these are your symptoms, you can add a little I-Gain to help out, but be careful and consider the rubber band effect that can have on the servo output level if you come up against a load that is suddenly removed. You can alter the position lock tolerance too, but that can directly affect the overall accuracy of the positioner. It will still try to achieve 0 position error, but will consider the move "Done" when it's within the lock tolerance and probably move on to the next step in the program. Again, this is just a knee jerk W.A.G. Another cause of "servo machine stopped with no errors" is an accel rate or velocity inadvertently set to zero. Not likely in your case since it's intermittent... Hope this helps Paul... Edited 29 Nov 2006 by OkiePC