Coolmuscle servo motors

  • Hello everyone,

    A quick backstory:

    We are thinking of reviving a multi-material 3D-printer (converted to dual-extrusion with two flexion extruders), Rova3D:

    Rova3D printer

    The printer came with a custom board, running (probably) a marlin based firmware. Out of the two versions we have the one with closed loop vector controlled servos:


    Now, we are thinking of upgrading this one with a Duet board. It would be a shame not to re-use the motors though. Currently, they are plugged in to the board using a pololu compatible adapter boards.

    Has anyone worked his way before with a similar actuators? In the documentation it is mentioned that the expansion header on the Duet has support for up to 5 external stepper drivers.
    If i am not missing something, it will also work for servo motor drivers with the stepper adapter board combo?
    Assuming, the current printer board sends step/dir commands and the on-motor controller handles it from there. And in the case where the control signals are implemented differently on firmware level, then i guess it will not work..

    Thanks in advance.

  • You should be able to treat these as external steppers. And, as you point out, Duet 2 has 5 outputs for externals.

    The onboard TMCxxxx drivers will not be usable for these motors.

    This also implies that a Duet 3 is not a good choice. It does not directly support external steppers.

  • @Danal Thanks for the reply. Yes, holding on to these motors is ruling the Duet 3 out. I guess i ll give it a shot for a test run on my own Duet before we proceed to purchase one for this printer. 🤞

  • DC42 has stated that expansion boards with 5V connections for external drivers are in the works; they are long term plan, no dates yet.

    So stick with D2 for now, and know that D3 will get there long term.

  • @Danal Thats great, Thanks for the info!

  • Moderator

    @Danal external boards may be closer than anticipated. I asked @dc42 when this came up last week, then didn’t get around to posting. He said

    yes we are but it's held up bu Chinese NY and possible by Coronavirus after that, because we get our PCBs from China like everyone else.
    we've hacked a few prototype tool boards to work with external drivers, but these are not generally available

    Im pretty sure It’s prototype boards he’s talking about, for testing, but that’s progress, right?!


  • That's great news!

  • For future reference.

    We tested one of these motors with a Duet 2 Wifi board and it was successful. It is actually a closed loop stepper that accepts step/dir commands and the on-motor controller handles it from there, therefore the wiring and config was pretty straightforward.

    Full conversion to Duet is on the way.


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