Undersized Stepper Motors?



  • Each time I home an axis, I get a very loud buzzing sound from the stepper motors with no motion, followed by very slow, "strained" motion. I've only gotten motion out of the Z-axis once. After that it's just been the loud buzzing. I've tried numerous combinations for current and speed settings, but nothing has had a significant impact or improvement. I'm wondering if the steppers do not have a high enough current rating and/or too high of an inductance for the drivers. Any thoughts or ideas would be much appreciated.

    X and Y-axis steppers:
    4.2 kg-cm NEMA 17 (# 42BYGH4807)

    • Step angle: 1.8°

    • Voltage ( V 😞 8

    • Current ( A 😞 0.5

    • Resistance (Ohms): 19

    • Inductance (mH): 32

    Z-axis:
    2x 2.4 kg-cm NEMA 17 (# 42BYGH011)

    • Step angle: 1.8°

    • Voltage ( V 😞 11.2

    • Current ( A 😞 0.33

    • Resistance (Ohms): 34

    • Inductance (mH): 48

    Additional Printer Properties:

    • Cartesian printer

    • 12V Power Supply

    • 8mm linear rails and M5 lead screws

    • X-Carriage: E3D Titan Aero with pancake stepper and V6

    • Y-Carriage: 6" x 6" x 1/2" MDF with aluminum build plate on top

    If you're wondering why I chose these motors, I recently dismantled my Printrbot LC when the Printrboard died and tried to keep as many of the leftover, non-wood parts as I could when I rebuilt (the steppers being among them).


  • administrators

    You are using motors with very high inductance and low current ratings. These are a poor choice for a 3D printer because they need high voltages to drive them at speed. With 12V power you stand almost no chance of getting them to work well enough for a 3D printer. With 24V power it would be better, but the speeds achievable will still be low. Use the EMF Calculator at http://reprapfirmware.org/ to work out the speeds at which torque will start to drop.

    The two Z motor outputs on the Duet are connected in series because that is generally better for low inductance motors. For your high inductance Z motors, connecting them in parallel would work better. Or, if you are not using the E1 motor output, you could connect one to Z (with the 2 jumpers in the spare Z connector) and one to E1, then use the M584 command to assign them both to Z.


 

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