Broken Shaft in Stepper motor

I was in the middle of a cut today and heard a pop noise and then later noticed that the left side of my gantry was “dragging” behind the right side. I paused my cut and found that the right side was locked in place, but the left side was able to slide forward and back as if the motor had been disconnected.

I isolated the wiring to the one motor to troubleshoot. Powering the GRBL back up made familiar “Motor On” noises, but the gantry would still slide. Using my keyboard to move the motor, I found that the outside shaft was turning, but the inner shaft with the GT2 pulley was stationary. Best I can tell, the motor shaft broke inside the stepper motor. I have never heard of or seen this. Has anyone else experienced a broken shaft inside a stepper motor? If it does indeed have a broken shaft, I dont imagine there is anything that can be done to repair it and my stepper likely need to be replaced?

That’s impressive. Time for a new one.

I had the same problem with my X-axis stepper motor (Nema 17) – I could see the motor spinning but the pulley wasn’t moving. When I took it apart, the shaft had sheared completely off. I can’t imagine producing enough torque to break the shaft.

Material fatigue due to a material imperfection to begin with. Hardened materials are strong but if they have an imperfection they can break easily.