Stepper Disconnection



  • Of course disconnecting stepper motors (Duet 2 Wifi) while they have power is a no no, but could the damage be reduced by ensuring certain pins are disconnected before others?
    In my case I have seperate docks for my extruder motors that can be removed with quick disconnection. The plan is to always power off before removing a stepper, but of course its just a matter of time before someone screws up.
    Since I am creating my own connectors for this setup, I can make a stepped disconnection if it could help.
    Not looking to cheat in any way, but to just reduce the chances of mishaps if possible.

    Thanks...Henry



  • Hi,

    And the reason for being able to remove the steppers is?

    Frederick



  • You may want to watch this video by David. https://youtu.be/uyWolKFzb-A

    I doubt if disconnection order matters since these are two independent coils.

    If you are concerned, one option is to add a protection circuit (e.g. diodes to ground and 24V rails) but I would expect the driver to already have it built in.

    Another options is having some interlock mechanism that will disable power when the extruder is accessed for removal.



  • I would think you can just disable the extruder stepper with an M18 E0. Then swap out your dock and re enable the extruder stepper by calling a short extrusion move.

    The heater would also have to be shut off and the fault would also have to be cleared when the new dock is in place. But that can also be done with a gcode.

    See,
    https://duet3d.dozuki.com/Wiki/Gcode#Section_M18_Disable_all_stepper_motors

    And
    https://duet3d.dozuki.com/Wiki/Gcode#Section_M562_Reset_temperature_fault



  • @fcwilt My printers have the ability to add and remove extra printheads depending on the makers needs. I use Zesty Nimble cable extruders, and the easiest way is to just be able to remove the printhead, cable, and stepper as one assembly (then hang it off to the side) rather than taking the whole cable coupling apart. This connection will handle the heater/therm, fans, and stepper wiring.



  • @HenryDara said in Stepper Disconnection:

    @fcwilt My printers have the ability to add and remove extra printheads depending on the makers needs. I use Zesty Nimble cable extruders, and the easiest way is to just be able to remove the printhead, cable, and stepper as one assembly (then hang it off to the side) rather than taking the whole cable coupling apart. This connection will handle the heater/therm, fans, and stepper wiring.

    I see.

    And you want to be able to make this change with power applied?

    Frederick



  • You should be able to do the hot swap with a macro. Disable the stepper, shutoff the hot end, Swap the hotend.

    Another macro can re-enable the stepper, remove the heater fault (that will appear).

    Simple.



  • @zapta Yeah, I think that would be the safest way. I already need a latch, so I can interlock it back to the Duet to tell when to disable the outputs. Not sure how long it takes to shut them down, but hoping it takes longer to unlatch, and begin to remove the stepper from its nest.



  • @fcwilt No, I want to prevent that. I am trying to find the best way to error proof the end user.



  • @HenryDara said in Stepper Disconnection:

    @fcwilt No, I want to prevent that. I am trying to find the best way to error proof the end user.

    Understood.

    Well the most foolproof way is to keep the end user away from the printer. 😉

    Frederick



  • @HenryDara said in Stepper Disconnection:

    I already need a latch, so I can interlock it back to the Duet to tell when to disable the outputs

    Maybe consider the other way around? Have the latch be electronic (servo or similar) and the only way to unlatch is to invoke the Duet macro? (which could be tied to a pushbutton right by the tool).



  • @Danal That would be nice, but I can have up to ten heads, so thats lots of servos or other. I am thinking of a "tool Present" signal for each head to a dig in, which can then drive my tool parameters somehow. I like that idea though. I could add an LED to show each extruders status. All green = all good. 🙂


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