Stepper issue with ramps (no replies)

Hi,

I have an issue I can't understand. My stepper on X axis suddenly began to kick this morning on direction change at approximately 60mm/s and above. It skip steps and make it impossible to print. I tried a lot of vref setting on the DRV 8825, 0.45 V, 0.6 V 0.75 V but it does not change the behavior. I dismounted everything to find the problem and it is not mechanical. It continue to kick even completely dismounted from the printer. Also at 225mm/s it just stop to move and skip steps, impossible to go faster, even with no resistance.

The stepper on Y axis can speed up to 500mm/s easily. I switched the two stepper and the problem is still on X axis, so the motors are alright. Then I switched the stepper drive and it is still X. In marlin, I have the exact same settings for X and Y.

#define DEFAULT_AXIS_STEPS_PER_UNIT {160.192, 160.192, 3200, 300, 300}
#define DEFAULT_MAX_FEEDRATE {600, 600, 10, 80, 80} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {5000,5000,25,3000,3000}

It leave me to suspect the ramps 1.4 but it is difficult to say why or how.

I tried everything that I could think of without success. If any body have an idea it would be very very appreciated.

Thanks