Problem losing steps only in one direction


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Thread: losing steps only in one direction

  1. #1
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    Default losing steps only in one direction

    I am running a GRBL controller with the infamous TB6560 driver with Nema 23 motors. Lately my Z axis will not always return to the zero position. To reproduce the issue I have a gcode file to simply moves the Z axis up and down 3 mm ten times and then back to zero. 25 % of the time it returns to 0, but 75 % of the time the return point is lower than zero. I have tried the following without success :


    1. changed the micro-stepping to full step, 1/2 step and 1/4 step
    2. reduced the feed rate - GRBL : $112 to 400 mm/s
    3. reduced acceleration - GRBL : $122 to 10 mm/s^2
    4. used shielded wiring to connect the Arduino to the TB6560
    5. lowed the voltage to 22 volts
    6. replaced with another TB6560 driver
    7. checked the couplers and mechanics of the Z-axis - it runs smoothly


    A replacement driver: DM556 is on it's way but wanted to see if there was any other experiments I could run. My X and Y axis have already been upgrades to the DM556 but they did not have this issue.



    Similar Threads:
    Last edited by junior2016; 06-24-2020 at 02:33 PM.


  2. #2
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    Default Re: losing steps only in one direction

    Hello.

    May I suggest that you double check the mechanics? If there is even a small amount of play at any of the links the cumulative effect can be high.

    There should be flats on every shaft to accomodate the screws but if there are no flats a rather loose screw might lead to link slippage. It is easily identifyable by removing the links and checking the shafts for scratches. If there are some then you can be certain that there is slippage.

    While that effect is sometimes hidden when dry checking any axis it is most notable when doing some actual work that adds load to the axis.

    In referring to the drives, could it be possible that your current settings might be set lower that what is required? Too low a setting could lead to missing steps. Try increasing to the next upper setting and if the problem still happens the try the next up.

    Not a matter of preocupation but remember that by increasing the current setting might yield higher temperatures both at the driver itself and the motor.

    I hope this helps.

    Regards.

    PS: I would start by changing the current setting as it will only take seconds to do. Remember to turn the machine or at least the drive off before making any changes.



  3. #3
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    Default Re: losing steps only in one direction

    BBMNet - thanks! It was indeed the mechanics. The set screw on the coupler for the ball screw end was slightly loose and had a little play. This caused a slight slippage on each directional change. I guess I can keep the crappy TB6560






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losing steps only in one direction

losing steps only in one direction