[Wolfpower]

Machine is old (1988) but clean and has no coat hanger duct tape chicken wire repairs. All components work and machine holds dimensions well. Lately, the Z axis shifts .030 up after a while of running. So it is like the z zero plane is now higher. At 50% rapid this never happens, only happens at 100% rapid. Never get any alarms. Restart the machine and everything is correct again. Swaped drive cards, checked cog belt for z drive, checked encoder set screws, checked ball screw, lube, hydraulic counterbalance, static Z axis load, control cabinet fans all work and cabinet is normal temp inside, z axis thrust bearing are smooth quiet, everything checks out. Checked z accuracy and repeatability and incredibly is very very good. The problem happens when in 100% rapid running a program. Sometimes it will go all day without a problem, other days is happens a lot. Has anyone had this issue in any direction xyz?

[Night Shift Wiz]

We've had similar problems. Usually turns out to be the encoder.

[Night Shift Wiz]

We've had similar problems. Usually turns out to be the encoder. Did you try swapping?

[Wolfpower]

I will swap encoders, I have an extra one. I posted this in case there was something I missed. Thank you for your help.