OkiePC
Lifetime Supporting Member
This is not really a PLC question, but I'm sure that some of you have dealt with this before. The problem is with A/B 1394 and S-Class motion controllers' overtravel inputs and trapping faults. When an overtravel fault occurs, the global fault code changes to a 3 and the axis status changes to 9. The motion controller will immediately jump to the fault routine, but as soon as the limit switch is Okay, the fault codes go back to normal. I've had two different situations in which an intermittent OT limit caused troubleshooting confusion. The fault handler was unable to identify the cause because it cleared up before any of the fault reporting logic could occur. On one machine it was a loose connection. On the other, it was a drive belt that was whipping the limit switch lever very rapidly (barely visible to the trained eye). The only way I was able to diagnose the first problem was to put a print block in the beginning of the fault routine and watch the terminal window and that only worked part of the time. I've tried copying the status words to user variables at the beginning of the fault routine, and this works occasionally, but most of the time (with the second problem especially) it's just not happening fast enough. The motion controller always detects the fault and jumps to the fault routine, but usually reports no fault. The maintenance techs scratch their heads for a while and then call me. Is there a way to programatically trap hard overtravel faults that is more reliable?
Thanks
Paul C.
Thanks
Paul C.