Inside the pulse coder, a glass or plastic disc with etched lines spins. If a shock (like a tool crash) cracks this disc, the encoder will send random signals.
: Open the control cabinet while powered to see the LED code on the Z-axis servo amplifier (look for 8, 9, or A). Verify Diagnostic Screens Fanuc 16/18/21 Series Diagnostic 200, 201, and 204 Fanuc 0 Series Diagnostic 720–727 Isolate the Component The "Repack" Drive fanuc 414 servo alarm z axis detect error repack
It should always be your first step before calling a FANUC service technician who will charge $500 just to walk in the door. Inside the pulse coder, a glass or plastic
Then:
When you say you disconnected the X axis from the drive, the alarm did not occur, did you disconnect the motor power cable (U,V,W) Practical Machinist Resolving this requires pulling the axis apart to
If the motherboard or SRAM battery dies during the re-pack downtime, the servo parameters (Parameter 2000 series) may be lost. Without these parameters, the control does not know how to "talk" to the Z-axis amplifier, resulting in a communication error (Detect Error).
Resolving this requires pulling the axis apart to inspect and "repack" (rebuild) the structural mechanics. Ballscrew Inspection and Re-balling (Repacking)