Step 2: Interpreting Servo Diagnostic Bits (No. 200 and No. 204)
Note which bits are set to "1". For example, if Bit 6 (OFS) is on, it indicates an abnormal current offset. If Bit 5 (FLD) is on, it points directly to a feedback loop cable disconnection. 2. Inspect the Physical Connectors and Cables
With the initial diagnostic data (amplifier display and DGN200 bits) in hand, the real work of pinpointing the failing component begins. The goal is to systematically isolate the fault to one of four main areas: the , the servo motor , the servo amplifier , or the control board/cable .
Note which bit is set to 1 . If Bit 5 or 6 is active, focus heavily on the encoder and feedback cables. Step 2: Inspect the Physical Servo Amplifier LED Open the main electrical cabinet door of the machine. Locate the FANUC Servo Amplifier Module (SVM). fanuc 414 servo alarm z axis detect error
The amplifier itself is not processing the signal from the encoder correctly.
| 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). |
Jim, the shop’s veteran lead technician, knew this wasn't just a simple glitch. A "414" alarm means the CNC has detected a serious issue—usually an or a short circuit in the servo system. 1. The Investigation Begins Step 2: Interpreting Servo Diagnostic Bits (No
This alarm typically stems from electrical or mechanical resistance that exceeds the system's design limits: Electrical Shorts
Before beginning any diagnostic work, you must follow strict safety protocols. Working with industrial servo systems involves high voltages and heavy mechanical components.
Regularly service cabinet cooling fans and change air filters to keep the servo amplifiers running cool. For example, if Bit 6 (OFS) is on,
When the CNC screen displays , it means the main CPU has lost proper feedback communication with the Z-axis pulse coder (encoder) or has detected an abnormal electrical state within the feedback loop. Primary Causes of the Z-Axis Detect Error
| Field | Detail | |-------|--------| | | 414 | | Message | SERVO ALARM: (Z-AXIS) DETECT ERROR | | Meaning | The software position detection system has detected an abnormal signal. Specifically, the Pulse Coder (encoder) signal is missing or corrupt on the Z-axis. | | CNC Suspends | Yes – Immediate feed hold and servo off. | | Applies To | Z-axis (usually the vertical axis – spindle head or knee). |