Stepper rattles above certain speed in Stealthchop

KP0005

I've been fighting with my extruder for about a week now, I hope someone can help me on this one:
I'm trying to run my extruder motor in Stealhchop only (TPWMTHRS is 1) because Spreadcycle produces a robotic sounding pulsating high pitched noise when moving, and accelerating moves (like retractions) like to skip steps when switching from Stealthchop to Spreadcycle. The motor is nice and silent until I hit about 23.83 mm/s, above which the motor starts vibrating and losing torque, which leads to skipped steps.

I initially thought this was due to some mechanical resonance from the step frequency, but the motor consistently starts to shake at the same speed on different microstepping settings (x16 with interpolation, x32 with interpolation, x64 without interpolation, x32 without interpolation). Also Spreadcycle doesn't seem to have this issue.

Is there anything I can do to either fix this vibrating behavior in Stealhchop or make Spreadcycle less noisy?

Veti

you can try and play with some of the advanced features
https://duet3d.dozuki.com/Wiki/Reducing_Stand-Still_Noise
try some of the marlin settings
{ <off_time[1..15]>, <hysteresis_end[-3..12]>, hysteresis_start[1..8] }
#define CHOPPER_DEFAULT_12V { 3, -1, 1 }
#define CHOPPER_DEFAULT_19V { 4, 1, 1 }
#define CHOPPER_DEFAULT_24V { 4, 2, 1 }
#define CHOPPER_DEFAULT_36V { 5, 2, 4 }
#define CHOPPER_PRUSAMK3_24V { 4, 1, 4 }
#define CHOPPER_MARLIN_119 { 5, 2, 3 }

are you on 24v?

KP0005

12V, would 24V help?

Veti

stealthchop is meant to be used with 24v. the torque drops rather quickly at 12v.
see https://www.youtube.com/watch?v=GVs2d-TOims
spreadcycle also tends to be quieter at 24v, but the noise level depends on the motors.

KP0005

Thanks, guess I'm getting 24V PSU

zapta

@Matej101 said in Stepper rattles above certain speed in Stealthchop:

The motor is nice and silent until I hit about 23.83 mm/s,

Do you have the motor's datasheet? I had similar problems with a ~8mh motor until I switched to a ~2mh motor.

With high inductance, the motor doesn't get the full current at higher speeds.

KP0005

@zapta 1.68A rated current, 1.65ohms phase resistance, 3.2mH inductance, 36N/cm holding torque. I have the 24V PSU on order so I can test if that fixes it.

KP0005

Alright, I wired up the 24V PSU and it seems to have solved my problem at least partially. The motor no longer loses torque in the range where I want to operate it. The vibration problem didn't completely go away but it now starts at a higher speed and it isn't as bad. Thanks for the help!