In 10+ years of working with Mach on numerous machines, I've never seen this one. When you zero the X axis, then G0X50, it moves 50". If you G0X0 it moves back 48.75". The error accumulates consistently as the length of travel increases. 50" will always produce an error of 1.25". 96" of travel will always produce the same error of about 2". The closer to zero the travel gets, the smaller the error. We know it's not a mechanical issue and to make it even more perplexing, if we zero on the other end of the table and G0X-50 followed by G0X0, it returns properly to zero.
Has anyone heard of such a thing? We're re-installing Mach3 since everything else has been checked OK. It's almost as if Mach is using different steps per settings for X- vs X+ motion. If it were something loose or random missed steps, I wouldn't expect a consistent error.
Thanks