Jerk each full revolution

[grafalex82]

I just installed Servo42C to one of my printer's axis. It is quiet and running basically well, except strange artifacts each ~30mm along the axis. These 30mm correspond to one full revolution of the motor.

The image shows just a few artifacts, but that is just because they seen under a certain angle. In fact it is visible on the whole side of the model each 30mm.

This is not a mechanic issue - the same motor connected to a regular TMC2209 makes surface without any artifacts. I also tried to move Servo42C to another axis, and the artifact moved along with the servo board.

The artifact does not depend on the speed. The model on the photo is printed with 3 different speeds from 50 to 100mm/s - the artifact is present on all layers (despite some of them printed with different speed)

I suspect that the issue is caused by some jerk each revolution.

Is there a way to fix the issue in any programmatic way?

[PanosPetrou]

This is a late reply, but it might help others facing the same problem. I think it happens because of high stepper rate in Marlin. The controller of these motors does not play nice with rates over 20KHz. See here: https://github.com/makerbase-mks/MKS-SERVO42C/issues/54