Stepper motor proximity to expansion cable

  • Hi everyone,

    I have another question for the gurus on here. I have decided as I do not have manual bed leveling and am relying solely on the auto bed leveling, that I am going to be adding another z motor taking me to 4. One corner is always about .4mm lower than the others and for the life of me I can’t sort it. It may not help but it is bugging me and want to try something. The question I have is one of the steppers will be about 10mm of the extension cable going between my duet and duex2. Do I need to worry about noise from the steppers interfering with the comms between the two boards?


  • administrators

    @samlogan87 There are multiple communication channels going over that cable. I2C for the port expander (I2C errors are reported in the latest firmware with M122) SPI to configure the stepper drivers (if this did not work then you would get driver errors) Step/Direction signals to actually step the drivers. Interference from the stepper motor would not produce a repeatable 0.4mm offset for one of the motors.

    To trouble shoot this I would start with ABL and mesh compensation off and manually level the bed to the nozzle at the three probe points and the center. If the bed is flat you will be able to do this, if it is not then you wont. Once you have a base line then you can enable ABL to keep the plane of the bed level, and mesh compensation to deal with any lack of flatness in the bed.

  • Hi @T3P3Tony ,

    Sorry I think you have misread what I wrote. I have not done it yet but was just wondering if I needed to be careful in the location, as if it could be a problem, I will have to shift my Duet board on the printer to keep it away from the stepper motor, which won't be the easiest thing to do. I might be able to get it the outside of the cable to about 20mm away from the stepper motor.

    Kind Regards,

  • administrators

    @samlogan87 Sorry for missing the point. Its not possible to say in advance if it will be a problem or not as there are so many variables. That said on my bigbox a couple of the stepper cables run reasonably close to the expansion cable with no ill effects and I don't recall anyone else reporting this specific issue. Much more common problems are poor grounding between the Duet and Duex.

  • @T3P3Tony

    Excellent thank you. I hope it won’t be too much of an issue as the currents are quite low. They are all nema 23 motors which are way too big for what I need but plans changed as I built the printer with the first thought only being 2 motors, then 3 and now 4. I have a big enough power supply but I will turn the current down a bit for the steppers which will also help with any interference I think.

    Once again thank you for your help