Nema 17 Motor adjustment on Kossel

Quick questions for the forum.

1. Will a metallic screw driver damage the stepper drivers if used to adjust the potentiometers while hot? If so where do you get a non-metallic driver locally?

2. My nema 17 stepper motors have a high pitched whine to them and when I home they make a pitch noise even after the slides hit the x, y, and z max limit swiches. What is the best means to adust this if that is not normal.

thanks

1. not directly but its very easy to slip on the pot and short the driver or the whole board. you can easily dremel your self a tool out of an old toothbrush or so.

2. they do that either because the are underpowered or just they do that anyway. depends a bit on the brand. i also experienced that the whine vanished after some hours of use.

A lot also depends on the type of driver. DRV8825 drivers always whistle like mad. A4988 not so much, if the current is set right. I normally turn them fully down and then gradually turn them up until the motors just move, then give then an eighth of a turn above that.