z motor loses strength?



  • I'm building a printer right now, with 3 motors for the z axis.
    (using duet 0.8.5 with expansion V0.2) On the expansion the 3 z motors are connected, and work together, i can individually move them if i want using M584, that all works.
    But for some reason, one of the Z motors loses power at random moments, and won't move correctly with the other motors.
    When the motors are stationary, and on holding power, i can rotate that axis easily by hand, where the other 2 axes give resistance.

    It seems the point where it loses power is quite random, but i hope you guys can help with a solution (the motor in question is connected to the expansion board on Drive6)


  • administrators

    It's most likely caused by a bad crimp connection on that motor cable. Try swapping that output on the DueX4 with another, and see whether the problem moves with the motor+cable or stays with the output.



  • I've switched 2 motors around, and i still get the same issue on the drive (so the problem moved to the other motor)(so it's not the cable nor the motor)

    EDIT: Also, when i power down and start up the system completely it works for a short while, until that motor loses power again


  • administrators

    @napalm1432 said in z motor loses strength?:

    I've switched 2 motors around, and i still get the same issue on the drive (so the problem moved to the other motor)(so it's not the cable nor the motor)

    In that case, it sounds like bad soldering on the motor connector, or on the driver chip, or an overheating driver, or a problem with the VREF feed to the driver from the digipot that sets the motor current.



  • Is there a way in which i can solve this? or would i need to get a new expansion board which would set me back another X euro's?


  • administrators

    Are you already using all 4 motor outputs on the X4, and all 5 on the Duet?



  • i'm using all on the expansion board, but i have 2nd extruder free, and regular Z connection free.
    EDIT: Issue solved, just changed drives!



  • Soo it was solved, and it sort of still is BUT:
    When i jog the Z motors they all work fine.
    But when i start a print, somehow one of the motors loses strength again, but when i takeover manually it works again......
    Getting quite sick of getting these lil bugs fixed
    edit: i'm testing my last open drive right now, but it's sad that i would keep losing drive after drive
    Edit2: issue remains after switching drives....


  • administrators

    When you used M584 to assign drivers to the Z axis, did you remember to redefine the extruder drivers too?



  • I'm currently only reassigning the axes in the homez.g file, and when I home manually everything is fine, only when i print a gcode it fails when homing.
    Do i need to reassign the extruder everytime?


  • administrators

    @napalm1432 said in z motor loses strength?:

    I'm currently only reassigning the axes in the homez.g file, and when I home manually everything is fine, only when i print a gcode it fails when homing.
    Do i need to reassign the extruder everytime?

    No, but you must reassign the extruders in the M584 command in config.g where you do the initial driver remapping.



  • i do reassign the extruder in config.g at the end of the file



  • I did some more testing, and a had a gcode made in the newer version of cura, because of the M106 command missing the P parameter, but it only fails on that motor with a file from this version of cura, before i used Cura 15.04.6 and in that version it doesn't have the problem with the motor


  • administrators

    @napalm1432 said in z motor loses strength?:

    i do reassign the extruder in config.g at the end of the file

    That should be done in the same M584 command that you reassign Z, and should be before any M906, M915 and M350 commands.



  • okay, i changed the config to reflect this change, but still having the same issue, right now it also happened with the older cura's gcode.
    It seems to not even be powered, might it help to include the extruder mapping in each M584?

    EDIT: Never mind this comment, forgot to change my homing code, i'll be back after this!



  • Yup my bad, it works now! (haven't tested with the newest version of Cura yet though)


  • administrators

    You don't need to reassign the extruders in all M584 commands that you use, just in the first one - because when you assign any driver numbered 4 or higher to be an axis, it keeps its default assignment as an extruder as well unless you redefine the extruder drives.


 

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