Tuning TMC2660 drivers for small geared Nema 11 extruder motor.



  • Hello,

    I've got a Nema 11 with a 50:1 gearbox for my extruder motor. It seems to have enough power to plow through anything within reason, but sometimes the motor seems to not extrude a tiny bit. The extrusions are about 80% perfect, but some of the time a ripple occurs, leaving a dotted line instead of a nice smooth extrusion.

    I've tried disabling interpolation, but I'm starting to suspect it may have to do with the deeper driver settings like timing or chopping modes. This stuff is way over my head, so I''m hoping for a bit of guidance.

    The motor I am using is here: OMC Nema 11 50:1 geared stepper (full datasheet on page).

    The motor is running at 600 mA (tried 400 and 500 too). I have a feeling the low current, and moderately high inductance may be causing issues.

    I'm not seeing any reports of underruns or errors after M122, as my speeds are quite conservative.

    Any ideas!?



  • What is the steps per mm on that? Jerk, microstepping? PA?

    @bot said in Tuning TMC2660 drivers for small geared Nema 11 extruder motor.:

    but some of the time a ripple occurs, leaving a dotted line instead of a nice smooth extrusion.

    Is there any correlation or repeatability to that some of the time?



  • @phaedrux
    Drive diameter is approx 35.5 mm, so steps/mm of 4678, 16x with interpolation on and off. No PA at the moment.

    Jerk in the ranges of 1-7 mm/s, accel in the ranges of 60-6000 mm/s/s. In the middle of those ranges seems to give the best performance, but I’m still seeing random undereztrusion.

    There is no pattern really, they are different each time I print the same gcode. I might have been sleep deprived when I started this. I don’t know why I fixated on the deeper stepper driver settings. I think it may be due to the fact that I’m extruding very small amounts and have not dialed my retraction settings well, nor the extruder accel/jerk so it’s causing the filament to ooze out and then leave underextruded sections.

    I’d still be curious to know how to tune the settings for odd motors, as I would assume the defaults are more aimed at the typical nema 17.



  • It sounds like a retraction/reprime issue. I would focus on slicer and retraction settings.

    With 50:1 you've got a lot of rotation needed to get much movement. With such a high steps per mm you will be limited in your retraction speed.

    https://wilriker.github.io/microstep-calculator/



  • @phaedrux

    Yeah. I run a 14:1 nema 11 (on my other printer) and I can get good retractions at only 5 mm/s 0.4 mm distance. I’ll have to figure out the best combo on this 50:1. I may also be running hotter temps so I’ll dial them back.


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