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Stepper Motors Walking / Creeping *sometimes*

Discussion in 'CNC Mills/Routers' started by El Duderino, Feb 23, 2019.

  1. El Duderino

    Builder

    Joined:
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    Strange problem.

    During a longitudinal cut (only x-axis moving), my y-axis steppers will start to creep. If I pause/stop the cut they will jump back into position.

    Here is a video of the problem:



    The frustrating thing is that I have been cutting lots of aluminum without this problem. I "solved" it once a week ago after lots of troubleshooting. It's back now and none of my troubleshooting is working.

    It will often start when the bit first contacts aluminum, so perhaps EMI/electrical?

    Troubleshooting:
    Adjust V-wheel tightness
    Ground shielded cables
    Remove router power cord from drag chain, away from stepper wires
    Add ferrite beads to stepper wires
    Test new DRV8825 drivers
    Adjust/balance driver voltage
    Change "step idle delay" to 255 (always active)

    PS - these threads have been unspeakably helpful to me - thank you all for sharing your knowledge!

    Other details:
    OX machine
    GRBL 1.1
    CNC Shield V3
    DRV8825
     
    #1 El Duderino, Feb 23, 2019
    Last edited: Feb 23, 2019
  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

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    Hi
    How hot are the drivers? If the Y driver overheats it will shutdown, maybe only for .5 second, allowing the tool pressure to move the gantry.

    Remember to ground shielded cables only at one end, what they call a 'star' configuration, one ground point, and everything radiates out from there.

    Otherwise 99% certain it is EMI. >-:
    Have you tried grounding the aluminum workpiece?
     
  3. El Duderino

    Builder

    Joined:
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    Solved! Thank so much for the help, David.

    Hope this helps someone else down the road.

    I had to connect the machine ( including the gantry and z-axis) to earth ground. Totally solved the problem.

    upload_2019-4-26_16-26-30.png
     
    David the swarfer likes this.

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