Broken Stepper Motor?

Today after completing a job, my X-Axis stepper motor failed to return to home. When I manually tried to slide the carriage, it resisted so I powered down, let it sit for a couple of hours and then went back to it. I just powered up and it looks like the rear shaft of the stepper is spinning but not the front attached to the pulley. Seems like the internal gearing is stripped.

I’m planning to order another one, any other things I should check first?

Check the two set crews on the pulley. Sounds like the pulley is slipping on the moter shaft.

The steppers do not have an internal gear. The shaft sheared? that would be a lot of torque.

Hmmm…the pulley set screws are secure. I can’t imagine torque that would have sheared the shaft. Perhaps the motor locked up? Could it be a problem with the Arduino? Y-axis motors move fine.

I did some forensic analysis on the stepper motor this morning. The culprit: sheared shaft. Not sure what caused it, though I’m guessing the motor locked up and I shifted the carriage.


That even looks like a material flaw. Not sure how it sheared that cleanly. Maybe Inventables will agree and you can get a replacement.


Due to the very defined circumferential break, and the domed surface of the pieces, i would hypothesize that there was a stress riser (step change in diameter or groove, or possibly a material flaw) that was being acted on by a strong bending moment from one direction as the shaft rotated.
An extremely overtensioned drive belt or misaligned bearing would exert such a bending force.
eventually, fatigue cracking would begin and progress across the shaft diameter.


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I had a shaft shear on me also, it wasn’t fun at all. Mine happened mid-carve too. I suggest when you do order a new one purchase the upgrade kit, part # 30773-06. The motors in this kit come with the pre-wired connections if you have one of the newer models, post 2016. Good luck!