Duet2 Wifi with my old CNC milling

  • Hello Everyone,

    I have an old hobby cnc milling machine. Right now it is running with some properitary mainboard over printer port and i use mach3. If possible id like to switch to the Duet Wifi in terms of ease of use and convenience.

    I bought a Duet2 Wifi board some time ago and i wanted to know if i can drive these Steppers (see images) directly with the duet Wifi board... or do i need some external drivers (because steppers are too strong , too high power consumption )

    I saw in the documentation that 2.0A (even 3) should be ok. Just wanted this confirmed with my setup, that i dont destroy the board in (longtime) usage. (There is also a third stepper for z-achses, but a small one )

    Stepper 1
    Stepper 2

    i dont know which voltage actually is used. Would it make a difference if 12 or 24V is used
    (in sense of that i cant use the board in any of these cases ) Dont have the possibility to measure voltage atm.

    Thanks alot to everyone ! Any thoughts are welcome.


  • Moderator

    The best reference for stepper motors is here: https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors
    You can work out all the various setting using your motor specification here (I think, do check!): https://catalog.orientalmotor.com/item/all-categories/tegories-pk-series-2-phase-stepping-motors-legacy-/pk266-e2-0a

    The main things are, yes the Duet Wifi should be able to drive these steppers, use 24V, and with the motor rated at 2.0A, and bearing this in mind:

    So the usual practice is to set the motor current to no more than about 85% of the rated current.

    Set your motor current in config.g to 2.0x0.85 = 1.7A


  • administrators

    From the datasheet that @droftarts has very helpfully linked to, we can see that that 2A rating is for unipolar mode. To drive them from the Duet, you will need to use a bipolar mode. I recommend bipolar parallel (because of the high inductance for bipolar series), for which the rated current is 2.8A. I suggest you try running them at 2.0A, then if you find you need more torque increase to 2.4A (which will require fan cooling of the Duet).

    CNC machines usually run at low travel speeds, so 12V may be sufficient VIN voltage; but if you don't yet have the PSU, choose 24V.

  • Moderator

    Oops! Didn't notice it was an 8-wire motor, I've got so used to looking at 4-wire. Thanks @dc42.

    You might find @wilriker maximum acceleration calculator tool useful: https://wilriker.github.io/maximum-acceleration-calculator/
    And the EMF Calculator here: https://www.reprapfirmware.org/


  • Thanks alot to everyone. We will give it a try. This way our Fablab gets maybe an upgraded and modern Milling (hobby)-unit with this great Duet2-Wifi board. As soon as there is some progress i will let you know and send you a nice video of it in action 🙂

    And thanks again for this incredible fast support !


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