Z motor starts vibrating when acceleration is high

hey guys!
I have a nasty issue with my Z motor when homing Z for autoleveling.without servo.
When the Z enstop is proving the bed after clicking for the first time it raises so fast that at the middle of this raising movement the motor can't cope up with the speed and starts vibrating but wont raise the plate.
Tweaking the firmware I managed to prevent this by lowering DEFAULT_MAX_ACCELERATION to 4
and HOMING_FEEDRATE to 30. But the homing is incredibly slow now.

I'd love to have my Z homing as fast as you show in your videos, what could be wrong???

Make sure you have the stepper driver set to at least 1 amp. The Z axis has a lot of weight to carry and can be easily overloaded. The default Smartrap feed rates should work very good. If not, then check the drivers.

How could I check that? I set my driver potentiometer to the maximum and still facing the same issue

Are you using a multimeter? You would have to set the negative to a ground pin and clamp the positive to the metal screwdriver. That way you can tune it while you see the value.

stepper calibration picture

You really can't go by potentiometer dial location. They vary from driver to driver. Do it this way and really be sure you are getting enough power and not under driving the stepper

Edited 1 time(s). Last edit at 07/08/2014 11:35AM by duranza.

That is very reveling...but I think I fried my driver by checking it current. It could be possible. How could I test if it's dead?

The only way to fry it would be to ground the positive. Try swapping the driver to the X or Y axis to see if it is dead. When I started I did manage to fry my extruder driver, but it was due to over-driving it because it was kicking back. Be careful not to lean the metal screw driver and touch the heatsink.

I should also add, do not by any circumstance try to remove/swap any wiring while the board is powered.

Edited 1 time(s). Last edit at 07/08/2014 04:09PM by duranza.

Look in your configuration.h file


#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 25} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for retracts

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