Need Help!- small tuning problem with stepper motors

[springlakecnc]

Hi Everyone,

I help people build their step and direction panels. I built one with stepper motor drives for a man that is about an 8 hour drive away from me. I always test them with my nema34 stepper motors. He is going to use Mach3 software, so i used my Mach3 to set up the panel and via phone conversation, he almost has the same set up values in Mach3, as i do. We didn't go over all the screens, just the pin numbers, and motor tuning.

He has a new computer, mine is a few years old. He has nema42 stepper motors.

The panel ran perfect for me, when i tested it with my nema34 motors.

The panel ALMOST runs perfect for him, But, only in X&Y axis (the Z runs good, and is geared different than the X&Y axis, for more power) when he changes direction, the motor takes off, slows down, then accelerates to speed. It is not losing position. If he keeps jogging in the same direction, say in 1" jog increments, the motor accelerates just fine, it only has the moment of slowdown when he changes direction. It is not machine backlash, because the motor clearly sounds like it slows down, than takes off. Increasing or decreasing the acceleration /deceleration in motor tuning doesn’t help. I am 99% sure the problem is a software setup issue.

Everything is sized correctly, and i have built about 50 of these for other people, so it is not my first. I simply am NOT a stepper motor guru.

I am having him check the software for a large value in backlash, which Mach's default is: Backlash runs at 20% of programed speed, and that sounds somewhat like what he is describing.

Any other Ideas???

Thanks for the help.

[ger21]

shuttle accel in general config controls backlash accel. Try setting it to .01 or .001