We have an older (1990) Mazak Laser that has had some geometry issues for the past couple years and might be getting worse. The problem only occurs when the the laser path changes directions. It makes the corners and even round holes of the parts look pretty bad. The best way I can describe the geometry is a wavy line that starts after it turns a corner and then fades out within a distance of about .250" to .500". At first we thought it was a ballscrew backlash but upon running a test we eliminated the ballscrew as the problem. Recently, I took the cover off the X axis servo and noticed the ballscrew "bouncing" back and forth when it changed directions. This lead us to believe that perhaps the servo motor was worn out. We also had a problem about two years ago that caused us to loose all the parameters in the control and we had to reinput them. Some people around here think that perhaps some of the parameters are not correct or need some adjustment. The link below is to a video clip that I took of the ballscrew's "bouncing" movement when changing directions.
I would greatly appreciate any help I can get on resolving this issue.
http://www.amfminc.com/VID00003.AVI