Upgrading Steppers for an Ender 3

  • Hey everyone!

    I've owned an Ender 3 for about half a year now, and after a couple videos about the Duet on YouTube and the fact that I'm constantly fighting with the available memory of the tiny atmega on the melzi mainboard, the noise and the artifacts caused by the low microstepping and the worse quality over USB and octoprint, I've decided to upgrade to the Duet.

    I already purchased a Duet Wifi 1.04 and I've been toying with the idea of using a Y-Joiner to print with 2 (or more) Materials.
    Which led me search for a second extruder motor.

    While searching for the motors, I also saw that 0.9° Motors are pretty cheap, so I thought, why not upgrade to those too.

    Now, the Ender 3 is currently running in this (stock) configuration:
    JK42HS40-1704 (1.8°, 1.7A, 40Ncm, 2.8mH) for E
    JK42HS34-1304 (1.8°, 1.3A, 28Ncm, 2.8mH) for X, Y, Z

    What worries me is that the 34mm stepper with a holding force of only 28Ncm is driving the Y axis. I've had to lower jerk to 10mm/s from 20mm/s else I would get missed steps and layer shifts, especially with a heavy glass bed on top and I'm not the only one with this issue.

    While searching on the forum, I found the 17HM19-2004S (48cm, 46Ncm, 2A, 2.8V, 3mH) recommended by dc42, however, while searching I also found these:

    JK42HM48-2404 - 48cm, 48Ncm, 2.4A, 2.4V, 1.8mH

    On paper, they seem better (lower inductance, minimally higher torque, less voltage) and with the calculation given on the wiki, they should achieve a higher speed.

    Would these be a good fit for the X, Y and Z?

    Next I'm wondering about the choice for the extruder motors. They will be equipped with a Bondtech BMG with a 3:1 Gear Ratio. Should I go with 0.9° steppers too, which comes with a reduced holding torque for the same size, or should I keep the 1.8° JK42HS40-1704?

    This 0.9 stepper (JK42HM40-1684) with the same size (40mm) has a torque of 33 Ncm vs the 40 Ncm of the JK42HS40-1704. Or I could also go with the JK42HM48-2404 from above? Would that be overkill?

    Edit: After finding this article in the wiki it seems like it makes sense to choose the 0.9, 33Ncm JK42HM40-1684 over the 1.8, 40Ncm JK42HS40-1704. As the the force for the 3:1 geared extruder doesn't need to be that high anyways and I would probably benefit from the increased resolution. Am I right?


  • Moderator

    I can't say if the JK42H is better than the 17HM19 for XYZ, but I use the 17HM19 and I'm happy with them on my corexy.

    For the extruder I would go with 0.9 stepper, since the extruder is where you might actually notice the increased step resolution.

  • administrators

    @devleon said in Upgrading Steppers for an Ender 3:


    That motor would IMO be just perfect for the Bondtech extruder, unless you want to use a 0.9deg motor. I use it in the Titan extruder on my delta (soon to be replaced by a Bondtech). The problem with using a more powerful motor on a geared extruder is that it helps to have the torque low enough so that if the nozzle is temporarily obstructed, the extruder skips steps instead of grinding the filament. But if you start with a high torque motor and reduce the current to reduce the torque, not only do the microsteps become less even, but the high rotor inertia of the larger motor limits the acceleration.