Prusa phase stepping and VFA is the hot point there. I’d waited for someone to show up results.
There we are:
So, looks like phase stepping decreases VFA a little.
*looks like slightly different filaments here
Best improvement at least for Klipper I had is with the vibration profile test film Shake&Tune.
It shows you where motor or other resonances kill your quality at what speeds.
So you can choose the “green” speed bands for different features and get way better prints.
I tested many different things but this made the (best) improvement.
But you have to disable slow downs due to layer time otherwise you might reach problematic speeds again.
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The torque from a stepper motor driven by a sinusoidal current will not be constant, even with a constant load-angle. Hybrid-stepper both have ripple current due to their varying reluctance, that is (approximately) proportinal to the RMS current, they also have cogging torque (also known as detent torque) due to the permanent magnets in the motor. The cogging torque is present even when no current is applied, this is the rotary-encoder-like clicking you feel when turning the motor by hand.
You can read a bit about this here: [JAC016] Analysis of a Hybrid Stepper Motor | Simulation Technology for Electromechanical Design : JMAG
Even if the ripple torque is low, and thus the deviation from the commanded path is low, because the disturbance is periodic it becomes very visible on the print. As the speed of the toolhead oscillates (due to torque/acceleration ripple) the flowrate and thus wall thickness does too, as the extrusion speed is constant.
I hope this helps understandig the problem a bit better, ptherwise I can maybe add a few more details when I’m not on the phone.