Fanuc 414 Servo Alarm Z Axis Detect | Error
To prevent the recurrence of a Z-axis detect error, implement these regular maintenance practices:
| Cause | Description | |-------|-------------| | | Broken wire, intermittent connection, or poor shielding on Z-axis encoder cable. | | 2. Encoder internal failure | A20B-2000/2001 series or alpha pulse coder failed (common on older machines). | | 3. Loose connector | JX5, JX6, or JFB connector on servo amp or CNC side. | | 4. Servo amplifier failure | Loss of 5V encoder power supply inside amplifier. | | 5. Noise interference | High-frequency noise from spindle drive, VFD, or poor grounding. | | 6. Battery voltage low | On absolute encoders – low battery can corrupt position data (often shows 310/349 first). |
If you have checked the cables, cleaned the connectors, and verified the mechanical integrity of the axis, but the 414 error persists, the problem likely lies in the or the servo amplifier module .
Look up (depending on the FANUC control series, such as 16i/18i/21i or 0i). fanuc 414 servo alarm z axis detect error
| 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. |
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When the Fanuc 414 servo alarm occurs, the machine may exhibit the following symptoms: To prevent the recurrence of a Z-axis detect
Low Voltage. The amplifier detects insufficient DC link voltage or control power voltage.
Ensure the Z-axis ball screw is properly lubricated.
| Alarm | Meaning | Action | |-------|---------|--------| | | Detect error (position coder signal lost) | Cable / encoder / amplifier 5V | | 411 | Excessive position error | Mechanical binding, servo tune | | 415 | Disconnect alarm | No serial communication at all | | 416 | Digital servo alarm | Internal CPU/ROM error in amplifier | | 436 | Soft thermal alarm | Overload or cooling issue | Servo amplifier failure | Loss of 5V encoder
is a frequent and often frustrating issue faced by operators of CNC machinery equipped with Fanuc controllers. Specifically, the "414 Servo Alarm: Z-Axis Detect Error" (or SV ALM: n-TH AXIS DETECT ERR where n corresponds to the Z-axis) indicates that the CNC system has detected a malfunction in the digital servo system controlling the Z-axis, preventing normal operation.
Coolant ingress into the Z-axis encoder cap or a pinched feedback cable causes signal loss.
Inspect the cable for tight bends, pinches, or abrasions along the cable track. Step 5: The Swap Test (For Multi-Axis Drives)
Use silicone or robust gaskets on all Z-axis cable junction boxes to prevent coolant entry.
Displays feedback and scale alignment errors.
