Duet 3 SBC Extruder skipping

  • My extruder seems to "stall" when the going gets a little tough. It just clicks and doesn't continue to push through. I can push it by hand or turn the wheel (BMG).

    ; Drives
    M569 P0.0 S1 ; physical drive 0.0 goes forwards
    M569 P0.1 S0 ; physical drive 0.1 goes backwards
    M569 P0.2 S1 ; physical drive 0.2 goes forwards
    M569 P0.3 S1 ; physical drive 0.3 goes forwards
    M569 P0.4 S0 ; physical drive 0.4 goes backwards
    M569 P0.5 S0 ; physical drive 0.3 goes forwards
    M584 X0.0 Y0.1 Z0.2:3:4 E0.5 ; set drive mapping
    M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
    M92 X100.00 Y100.00 Z400.00 E408 ; set steps per mm
    M566 X600.00 Y600.00 Z24.00 E300.00 ; set maximum instantaneous speed changes (mm/min)
    M203 X20000 Y20000 Z600 E2000.00 ; set maximum speeds (mm/min)
    M201 X3000.00 Y3000.00 Z600.00 E5000.00 ; set accelerations (mm/s^2)
    M906 X900 Y900 Z900 E900 I30 ; set motor currents (mA) and motor idle factor in per cent
    M84 S30 ; Set idle timeout
    M671 X-40:460:460 Y150:310:50 S9 ; leadscrews at rear left, front middle and rear right

  • Moderator

    What are the specs of the motor?

    Is 900ma 85% of the rated max for the motor?

  • @Phaedrux The manufacturer just got back to me. The stepper motors are all 1.5 amp. So Need to change all of them.

  • @Phaedrux So it's 85% being then 1275 is that correct ?

  • Moderator

    Yes. I'm not sure what the current step size is for the Duet 3 but 1275 might get rounded down to 1250 or 1200, so I would probably just go with 1200 or 1300.

    On duet 2 it's 100ma and on the maestro it's 50ma steps.

  • Moderator

    On Duet 3 MB6HC and EXP3HC it is 26.2mA.

    On Duet3 Mini5+ it is 74mA (provisionally), rounded down.

  • @Phaedrux Is there a a formula for figuring that out ? I have the Duet 3 6HC. What does that mean for my setup to put into config.g

  • Moderator

    You can use 1275mA in your config.g and it will round to the nearest it can support, which in the case of the Duet 3 should be quite close.

    There's no formula that I'm aware of, but it does have to do with the fundamental characteristics of the drivers themselves and possibly a bit on how our interface to them is designed.

    In general though, I wouldn't worry about the exact figure too much. The rule of thumb is to target somewhere around 60-85% of the rated max of the motor, but you'll need to do some testing on your own machine to determine the sweet spot. The higher the current the more torque and microstepping accuracy, but also the more noise and heat.

    If 85% is the max you might want to use for printing, try and find the minimum viable current that produces reliable movement. That should be your current used for homing to prevent damage in case of a crash. For your idle hold current you'd want to set it as low as possible without losing holding torque so that the motors retain position.

    Personally, I set the M906 value to the rated max of the motor and then use M913 to reduce that to a target percentage as needed. 80% for printing, 40% for homing, 15% for idle, 50% for normal jogging around. I don't even know what the exact value in mA that it's getting in any scenario, I just let it figure it out.

  • @Phaedrux Where do you change all those at ? I would love to see your config files 🙂

  • Moderator

    I have a set of macro files with the M913 commands in it and those get called as needed.


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