Uncouple the Z-axis motor from the ballscrew. Unbolt the coupling. Now, try to power the machine with the motor uncoupled.
| Step | Action | What it tells you | |------|--------|-------------------| | 1 | Power off. Swap Z and X servo amp (if identical). | If alarm moves to X → amp bad. If Z still alarms → motor/cable. | | 2 | Disconnect motor power/encoder, inspect pins for corrosion. | Green/black pins → connector issue. | | 3 | Megger (insulation test) Z motor windings to ground. | Low resistance (<5MΩ) → motor internal short. | | 4 | Check Fanuc parameter 2020 (motor model) – corruption rare but possible. | Wrong motor ID → 414 alarm. | fanuc 414 servo alarm z axis detect error
While this alarm can happen on X, Y, or Z, it’s most common on the Z-axis because: Uncouple the Z-axis motor from the ballscrew
| Diagnostic No. | Meaning | Normal Range | | :--- | :--- | :--- | | DGN. 200 | Position error (current) | Should track command | | DGN. 203 | Command pulse count | Changes when moving | | DGN. 204 | Feedback pulse count | Must match 203 | | DGN. 205 | Load meter % | < 150% normal | | Step | Action | What it tells
A floating ground between the CNC and the transformer creates a voltage potential. The 5V encoder signal sees 2V of AC noise superimposed. This corrupts the feedback, triggering a detect error.
Unlike X and Y axes, the Z-axis is vertical. Gravity is an implicit load. If you have a vertical mill, the Z-axis brake is engaged to hold the spindle head up when the servo is off. A 414 alarm usually precedes a Z-axis drop. When the servo shuts off, the brake must hold. If the brake is worn, the head can crash into the table or part. Never ignore this alarm without first blocking the Z-axis (place a block of wood or a jack under the spindle head).