10/08/98
This is more of a debugging than a repair. When our machine arrived, the Z-axis home switch and the Z-axis encoder home signal were set very close to each other. What happened today is that the home switch must have made contact a fraction of a millimeter too late, causing the machine to home .200 inches (one pitch of the ballscrew) too far back. Subsequent homings did not produce this result, but the settings were too close for comfort.
The remedy is simple: uncouple the motor, rotate the ballscrew 180 degrees, and recouple the motor. This puts the home switch around .100 inches ahead of the home pulse, providing the home switch with a generous tolerance to work within. We unbolted the sliding cover to gain access to the coupling. After recoupling the motor, we re-homed and proceeded to find the limits to movement and redefined the Z-axis soft limit parameters P307 and P308. (This redefining is required any time a motor is removed.) Fortunately, we were between jobs, otherwise, we would have had to touch off all of the tools again.