[RJ02]

I have a 30" x 48" cnc router built from a kit. It has aluminum extrusions framework and aluminum panels for gantry and two ball screws on the Y axis, second one slaved to first one in Mach3. Problem is when calibrating the Y axis in Mach3, when I get it as close as possible, then when return to where zero was and reset it to xereo, I run it out a given distance and it might be right on but then return to zero and its not on zero by about an 1/8". Or I might have it set on zero and run it out a given distance and it might be off about 1/16" to 1/8". I checked the couplings on the stepper motors and there doesn't seem to be any play there. Seems like I'm chasing my tail and getting nowhere. Any suggestions? Thanks in advance.

[awerby]

You might be losing steps. Check for mechanical problems first, like a sticky axis or sloppy bearing, and if nothing's wrong there, reduce your acceleration setting on the Y axis by about half and try again.

[RJ02]

Everything seemed tight and I reduced the acceleration down to 2. Still was doing the same thing. I got to looking closer at the Y axis couplings and one was seperated slightly. (spider couplings) Couldn't tell whether it was slipping or not but took it apart and cleaned everything and put the coupling back on close together and tightened the set screws real good and it seemed to have fixed the problem. At least for now. Thanks for the suggestions!