Minimum Viable Duet3 CNC Hardware



  • Hey all!

    I am working on a PrintNC build and happen to have a spare Duet3 that I intend to use for the PrintNC.

    It uses a VFD Spindle, which I intend to use a PWM to 0-10V board to adapt for Duet3 use (Something like this: https://www.amazon.com/DAOKI-Voltage-Converter-Interface-Switching/dp/B081W4NTML .Thanks to folks in PrintNC discord for this tip).

    As for powering the steppers, I assume the thing to do is 32V input for the 5160s, correct?

    Does anyone have suggestions on a solid 32V PSU that would be able to power some beefy Nema23s?

    So to summarize, the list of needed hardware as I understand it:

    • Duet 3
    • PWM to 0-10V Board for VFD control
    • Nema 23s for each axis
    • Spindle (In my case, a 2.2Kw VFD spindle)
    • 32V Power Supply
    • Endstops

    Is there anything else that would be useful on the hardware end in relation to running a CNC using a Duet 3?

    I think having a known good hardware setup for each CNC size/class may be nice, then people can jump right in and riff on it as desired.



  • Welcome. I have a printNC but use external drivers with the STM port of RRF.
    Don’t know if any PSUs off the top of my head.
    The Duet 3 already supports VFDs natively so you don’t need the converter board.
    PM me and I can share you my config etc.
    I’m on discord on the printNC channel under this username


  • administrators

    the Duet 3 6HC has a 0-5V PWM output that can be used to drive a voltage converter like the one linked, It does not have a direct 0-10V VFD driver on board.

    Other than that I am not familiar with the printNC.



  • Hello,

    I built a CNC machine recently using these components and a duet2. I had issues with the PWM converter you linked to. I would recommend this one instead. Both, however, say limit 30V, not 32V.

    I use two of those PWM converters, one on E0heat to enable spindle on as my VFD requires a 10V signal input to do so, and one on E1heat for spindle speed. The Duet uses the difference between Vin and E0- or E1- for the PWM signal. That means E0- and E1- start at Vin (no PWM) and goes down to 0 (diff = Vin = max PWM).

    The PWM converter board you linked to cannot handle this. It only works if both Vin and E0- or E1- start at 0V/PWM, and E0- or E1- goes to Vin. You can enable this using !E0heat in RRF3, but I would not do this. There is a dangerous issue with this setup. Let's say you have a problem and you hit the emergency stop button to reset the board. There is a brief moment, maybe before the !E0heat in the config takes over, that E1 and E0heat briefly pulses to Vin. The board you linked to sees this as max PWM and Spindle On basically turning the emergency stop into a temporary spindle on at max speed button. This isn't a problem starting up the machine since the VFD takes longer to come online. But any reset where the VFD is ready to go and you E-Stop, boom.

    I would suggest NO prox sensors rather than NC for redundancy and I am also using an 8 channel relay to isolate between prox sensors and z-probe from the duet.


  • administrators

    @SDJ said in Minimum Viable Duet3 CNC Hardware:

    I use two of those PWM converters, one on E0heat to enable spindle on as my VFD requires a 10V signal input to do so, and one on E1heat for spindle speed. The Duet uses the difference between Vin and E0- or E1- for the PWM signal. That means E0- and E1- start at Vin (no PWM) and goes down to 0 (diff = Vin = max PWM).

    In RRF 3.2beta we've changed the way this works, to be more compatible with typical VFD spindle controllers.


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