CoreXY randomly losing motor direction



  • Very pleased with the Duet board. Ordinarily, this thing runs smooth as silk. Recently I'm having a problem,

    The motors seem to lose sync and move diagonally, and very rough at that (See attached video)

    I noticed this sometimes (not always) happens when I cancel a print and attempt to home.

    Video attached. The head is supposed to home Y, by moving from right to left, with the homing switch being visible on the left side of the print head. Instead, it moves diagonally, and crashes...

    It prints fine most of the time, anyone have experience with this problem?

    https://streamable.com/pzb4k



  • Tighten the belt. The front left belt in the recording is loose.



  • Good eye on that belt. I tightened it down but the printer still moves rough and diagonally.

    I tried detaching that belt and looked at the corresponding motor. When I advance X+10, The motor doesn't spin properly, it seems to gyrate back and forth. I know the two motors work together to drive the head but thought this looked unusual.

    https://streamable.com/oqcrm

    Any other ideas? Could this be related to having the motor torques set improperly? I can post that part of the config file if that makes sense



  • Just saw a spark from blue wire inside the Molex connector when I flexed the wire. This may be the culprit, loose crimped connection

    I will let you know if this fixed it or not



  • Broken motor connections can destroy the motor driver chips. Test thoroughly after fixing the cable/connector, and don't be surprised if there's a problem.



  • Problem solved!

    It turned out it was indeed a loose or broken wire crimp connection on the stepper's blue wire, right at the Molex connector.

    I'm amazed it printed properly for as long as it did...

    Thanks for all the help.


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