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Problems with Z-stepper

Discussion in 'Motors' started by Giarc, Jul 23, 2016.

  1. Giarc

    Giarc Master
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    I am baffled. My Z-stepper, upon completing a move up, rotates counterclockwise about 2 degrees-ish. Upon moving down, when it stops, it rotates clockwise about 2 degrees-ish. I tried swapping it to another driver, and it did the same thing. It appears that all the wiring is secure and proper. It is a NEMA 23 175 oz. I have not had issues with any other motor
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
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    What controller are you using?
    Is backlash compensation active?
    Does it disable the driver after a short timeout?
    Does the driver have a power save mode that reduces power after the motor stops?
    What micro stepping is in use?
    Does it still do it with more or less micro Stepping?
    What voltage and current is the driver using?
     
  3. Giarc

    Giarc Master
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    I am using GRBL Panel and a protoneer shield with drv8825 drivers. I believe I am using 1/8 micro stepping. I would have to verify. I have not tried any other micro stepping options yet. That was going to be my next step (no pun intended). Voltage is 36V I set the Vref of all drivers to a little over 1V. I used the formula Current Limit = 2*Vref.

    As for these:
    Is backlash compensation active?
    Does it disable the driver after a short timeout?
    Does the driver have a power save mode that reduces power after the motor stops?

    Let's just say I need to do some more learnin'.

    I have some of the DQ542MA Stepper Motor Drivers I had purchased awhile back when there was discussion about those (http://www.openbuilds.com/threads/openbuilds-ox-cnc-machine.134/page-90#post-20304) and the THB6064AH. I may switch over to them. I was trying the DRV8825s because I was considering another build that would use larger motors, but I think I will use them now and use the DRV8825s for a 3d printer. Now that OB has the larger drivers, they can be easily replaced.

    Also, thank you for the following information you posted in my build thread. I believe I will find the solution from that:

    http://www.openbuilds.com/threads/lead-screw-driven-ox-derivative-850x1500.6517/
     
  4. Giarc

    Giarc Master
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    David the swarfer likes this.
  5. David the swarfer

    David the swarfer OpenBuilds Team
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    great. in the other thread I gave the solution for TinyG since you mentioned using that.

    Basically, if you are using microstepping you cannot be sure of getting back to the same place if you disable the drivers.
    The TinyG setting that keeps the drivers enabled during a run and for some time afterward is great, wish GRBL could do that. But it does mean that if you are running a multifile job, maybe with tool changes, you will need to change tools within the timeout period or lose the X0 Y0 setting.
     

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