Oscillations on halting

Graham,

All step motors have its own mechanical resonant frequency.

https://phidgets.wordpress.com/2014/07/28/how-to-avoid-resonance-issues-in-stepper-motors/ gives a clear explanation about the stepper motor resonance at certain speed.

When a stepper takes a single step, it will overshoot its target destination slightly and will oscillate a bit before settling down on target. This is due mostly to the inertia of the rotating mass briefly overpowering the magnetic field of the motor. This isn’t a big deal by itself but when you start chaining multiple steps together to get a larger movement this oscillation occurs at each step taken on the way. If the frequency that the controller is outputting new step commands to the motor matches the natural frequency of the motor then the oscillations will tend to become more severe as they propagate through the motor. Eventually they are so large that they will overpower the magnetic field for long enough on a given step to miss the subsequent step command, and you begin missing steps. Since steppers are typically run in open loop, the controller has no knowledge of these missed steps; The result is the motor will not get to its destination successfully. The effect can become so pronounced that the motor loses torque completely and stops rotating. Depending on the synchronization of the steps, it can even reverse the direction of rotation.

According to above analysis: one option is changing the natural frequency of the motor, such as: adding load(motor mechanical resistance) or "Overall, provided you know about the problem it is fairly easy to avoid. The best thing to do when you get a new stepper is to quickly run it through the available velocity range and find where the motor has trouble keeping torque. That is the region you should avoid in your application."

Another option is reducing each micro-step overshoot, would you try different output current setting or micro-step setting?