Overstepping/Understepping Error



  • Hi,

    Don't know if anyone has ever come across this:

    0_1526612639037_stepper_driver_problem.jpg

    While controlling the printer manually from the web interface or from Repetier it seems to function normally. Sending GCODE moves the printer the desired distance in all three axes. Once a print is loaded and it begins running GCODE it turns circles into ellipses and misplaces almost entirely the infill/bottom layers within the brim.

    This printer (running on Duet3d Wifi) has moved from England to the US and the Y-axis runs on an external stepper driver due to the power requirements of the corresponding steppers. Besides a transatlantic move the only other real change is updating the firmware from 1.20 to 1.21 but as I've not seen any other similar issues I've tentatively ruled out firmware.

    Any help or thoughts welcome.

    Thanks

    Nate


  • administrators

    It could be that your M569 timing parameters are not right for your external stepper drivers. Firmware 1.21 allows you to set 4 different parameters, whereas previous firmware provided a single value. Check the direction-to-step setup time in particular.



  • @dc42 said in Overstepping/Understepping Error:

    It could be that your M569 timing parameters are not right for your external stepper drivers. Firmware 1.21 allows you to set 4 different parameters, whereas previous firmware provided a single value. Check the direction-to-step setup time in particular.

    Sounds like this might be the case.

    Is there any documentation you can direct me towards that might clarify parameters like these:

    "Taa:bb:cc:dd (firmware 1.21RC5 and later) Minimum driver step pulse width, step pulse interval, direction setup time and direction hold time, in microseconds"

    Would it be the within the stepper driver chip information (Toshiba6600) ?

    thanks


  • administrators

    Yes, it will be on the datasheet for the driver or for the chip on which the driver is based. But to see if that is the problem, temporarily try T10 in your M569 commands for the external drivers. If that solves the problem, refer to the datasheet to find a more optimum setting.



  • @dc42

    T10 is a definite improvement but not exact.

    Toshiba6600 doesn't seem to have step pulse width etc or am I missing it?

    Is it " Minimum CLK pulse width CLK 2.2 μs"

    Thanks


  • administrators

    @madeinta1wan said in Overstepping/Understepping Error:

    @dc42

    T10 is a definite improvement but not exact.

    Toshiba6600 doesn't seem to have step pulse width etc or am I missing it?

    Is it " Minimum CLK pulse width CLK 2.2 μs"

    Thanks

    Yes, minimum step-high and step-low times are both 2.2us. Strangely, the datasheet doesn't give the setup and hold times for the direction signal. That probably means they are low. So if you use T2.2 that will set all 4 values to 2.2us, which should work.

    Another likely reason for your layer shifts is that your maximum speed (M203), acceleration (M201) or jerk (M566) setting is too high for the axis along which the shift occurs.

    Yet another possibility is a bad connection in the wiring for the motor that drives that axis, or a fault in the stepper driver.


 

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