Stepper 0.9 deg - very noise

Well, @DrumClock is experiencing stepper resonance. Every stepper motor has it. The magnitude (and the acoustics) of it will depend on the specific stepper motor and the mass (inertia) that it is moving. You can read about it here (and in many other places):

What is stepper motor resonance and how can it be avoided?
Solutions to Reduce Stepper Motor Resonance

In practice, my own experience has been that 0.9 degree steppers are more likely to resonate when used at stepping rates typically used in my 3D printers. This applies both to my heavily modified CR-10S Pro and my Voron 2.4 that uses 0.9 degree LDO A/B steppers. I have not spent much time on it to determine exactly why, beyond avoiding stepping rates close to this resonance. However, as one of the above linked articles suggest, the magnitude of this resonance can be somewhat decreased by increasing the micro-stepping, but it cannot be totally eliminated.

When trying to avoid the resonant frequency by changing the stepping rate (print speed), DO NOT change the print speed by full multiples. Chances are that you will land in harmonic frequency band (range) which will also excite the same resonance. So, if you hear resonance at 50 mm/s, try adjusting the print speed to 55, 60 or 65 mm/s, but not to 25 mm/s or 100 mm/s.

Coincidentally, approximately 50 mm/s in XY plane was quite noisy on the Voron 2.4 when using the original LDO-42STH40-2004MAH(VRN) 0.9 degree steppers, but the revised LDO-42STH48-2004MAH(VRN) 0.9 degree steppers are much quieter overall and tend to resonate a different frequency. I have not bothered mapping their resonance, because it is not anywhere bad enough to bother me. In addition, the 1.8 degree Z steppers also resonate and can be quite loud on the Voron at certain Z feed rates, but I don’t recall what the rates are since I configured them out (meaning the homing speed and max speed are not anywhere near the stepper resonance).

Note that @dmbutyugin proposed a potential firmware based mitigation for stepper resonance here:

[Proposal] Forbidden velocities for printer steppers

Cheers,
Peter.

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