Z Axis 2 Parallel Motors Synchronization



  • Hi,

    We are using 2 ball-screw, 2 LM guide and 2 Motors in Z Axis.

    1. With only one Ball screw and one LM, one 5.5Kgcm stepper motor can able to take the load.
    2. But with with 2 Ball screw and 2 LM parallel with each other, 2 same motor is not able to take the load.

    I think there must be issue with synchronization of two motors.
    Any one know how to resolve it ?


  • administrators

    Why have you wired your two Z motors in parallel, when we already provide 2 Z motor connectors wired in series on the Duets? We wired them in series for a reason - so that each motor gets the full current, not half the current.



  • Sir we have wired the motor in two different pins only, in series.

    our problem is when we run it in rapid (F6000) it will run 10-12mm and will stuck.

    with one motor Z Axis can run on F6000 Speed rate.


  • administrators

    100mm/sec is very fast for a Z axis. I expect the driver supply voltage isn't high enough to maintain sufficient torque at high speeds, especially with 2 motors in series. See https://duet3d.com/wiki/Choosing_stepper_motors#How_to_work_out_the_power_supply_voltage_you_need.



  • What is the maximum speed at which my printer can run, having stepper motors (1.5A current), torque 5.5kg/cm2 and using external power supply 24V?



  • Duet's X Y Z Motor Drivers and its capacity is same or different ?



  • @jaydevdave:

    What is the maximum speed at which my printer can run, having stepper motors (1.5A current), torque 5.5kg/cm2 and using external power supply 24V?

    That depends on the mass you are trying to move, the rate at which you accelerate it and the length of the move. Also for printing moves, the speed will be limited by the rate at which you can extrude filament which in turn is dependent of how fast you can melt the filament.



  • @jaydevdave:

    Duet's X Y Z Motor Drivers and its capacity is same or different ?

    The driver chips are the same for all axes.



  • Even on no-load condition, the two Z motors are not able to generate sufficient torque. Rated current being 1.5A with a torque of 5.5kg/cm2 and using 24V supply. What could be the reason for it? And what could be the solution for the same? Should I increase supply voltage or should use Motors with higher rated current?
    Please find the link to the video wherein no-load condition the z motors are not generating proper torque.

    https://drive.google.com/open?id=1I50zJb8WMD2IF8rmksil2842Gv6Ds2Q4



  • No doubt David will be along soon but from that video I'd say there has to be something wrong with either one of the motors or the wiring.



  • The same motors run when connected on X and Y axis respectively and that too with high speed of 100mm per second.


  • administrators

    @jaydevdave:

    What is the maximum speed at which my printer can run, having stepper motors (1.5A current), torque 5.5kg/cm2 and using external power supply 24V?

    See the link that I posted in my previous reply for how to calculate this.


  • administrators

    @jaydevdave:

    Duet's X Y Z Motor Drivers and its capacity is same or different ?

    All the same.



  • The same motors run when connected on X and Y axis respectively and that too with high speed of 100mm per second. why so?


  • administrators

    @jaydevdave:

    The same motors run when connected on X and Y axis respectively and that too with high speed of 100mm per second.

    The maximum speed achievable is lower when you have two motors wired in series. But why are you trying to run your Z axis at 100mm/sec? Z doesn't need to move fast.



  • We having two Y motors which have been swapped with the Z axis. So Two Y motors being connected at the Z axis and we need the speed of 100mm/sec.
    Stepper motors Rating 1.5A
    Power supply 24V.
    How can it be achieved?


  • administrators

    Try connecting them in parallel to just 1 of the connectors instead of in series using both connectors, and setting the current to 2A.

    EDIT: alternatively, if you have any spare motor driver outputs left, connect them to separate outputs, use M584 to tell the firmware to drive both together, and use the existing current setting.



  • Driving both the motors from a single connection(parallel) instead of two is safe? I hope it won't burn out the driver right?



  • We having two Y motors which have been swapped with the Z axis. So Two Y motors being connected at the Z axis and we need the speed of 100mm/sec.
    Tried what dc42 mentioned in the previous comments. We do not have extra driver nor it is working in parallel connection.
    Should we increase the power supply or should I use 3A rated stepper motors?

    Current motor having rating of 1.5A
    Torque 5.5kg/cm2
    Power supply 24V.

    How to do it?


  • administrators

    Like I said, connect them in parallel to a single stepper motor output, and try 2A current. The drivers are current-limited so it is safe.

    What is the steps/mm for that axis?


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