Stunning stepper motor

Hi repetier,

My scara project is start running now.
I add new command g5 rotate arm & forearm individually.
Homing route is done too, but i have a problem with stepper motor.

My step per degree is 480, for slow movement it's okay but for fast movement it stun.
I've tried to change the motor, the result is the same.
So i think it must be rotating too fast, more than the stepper ability.

I've tried to unplug microstep jumper and lower step per unit to 240 and 120, but it doesn't work. It still stun.

So, how to fix this?

And there is also a strange behaviour of the stepper for rotating long distance. It move and stop 3 times then move smooth to endstop.

Please give me advice. Thx


  • It is normal to have some stops on first move. This is due to the fact that you split the move into smaller moves and the first moves are planned befor optimizing the next moves. So first moves go back to save end speed and start from there again. Once buffer is filled this normally disappears, just as you described. Depends a bit on speed and your buffer sizes.

    Be aware the firmware has limits for speed. In avr you can maybe have 25000Hz and on due 250000Hz. Apart from this the force may be too high so motor stalls (I guess this is what you mean with stun). It also might be acceleration being too high. Problem is that acceleration is computed in cartesian coordinates and motors have to follow, so it might even work in some areas and other not depending on translation to rotation speeds.
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