I had a similar problem and I have Ball Screws. It was only with the X axis. I determined like PoppaBear10 said in his post that the timing pulley on the Stepper motor was coming loose. After I re-tightened it I had no more problems. However, on my Z-Axis the DRO was always one or two thousandths off. This was due to the DRO shaft being at a slight angle. I placed a washer to space it out more and it is accurate now. So you might want to recheck your X-Axis DRO shaft and make sure it is perfectly straight with no bends or off-angles.
Casey |