Z axis is frustrating me *$#@$%^&

[aercam]

I have a situation I am at my wits end with and need some help.

I just converted my manual Sherline 5000 to CNC using HobbyCNC 200 Oz in steppers and their board.

I set it up ala instructions on Mach3(that is what I am using) and the X and Y axes are running just fine. No problem moving those axes to any dimension. Now the Z axis!!!!!! It moves down two or three times the dinemsion called out. Moving up it only moves about half of the dimension called for.( z.250 yeilds z.125 most of the time.) I added helper springs to the axis and it did not help at all. I changed to a belt drive reduction (2.2:1) and it didn't do any good. Backlash is not noticeable.

Does anybody have any idea what may be up with this axis? I really would like to be able to control by programming rather than doing it manually.

Jim

[Dman]

Maybe try to increase the accel time on the axis. I know on my Homemade CNC the z will lose steps if the accel is set to fast on the way up but runs fine on the way down.

[ignatz]

What power supply are you using?
What stepping mode is the Z axis set to?
Have you tried different motors on the Z axis?