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CNC Machine Alarm Codes & Diagnostics

Master diagnostic guide for Fanuc, Haas, Mazak, and Siemens controller alarm codes. Includes root-cause diagnostics, electrical telemetry faults, and step-by-step restoration procedures.

Controller Diagnostic Database
Fanuc Alarm 414 X-Axis Digital Servo Alarm (Detect Error)
Alarm

Servo amplifier detected abnormal electrical or mechanical current, encoder pulse loss, or drive module fault on X-axis.

Potential Root Causes

Motor power cable short, cable ground fault, encoder failure, damaged IPM module in servo amplifier, mechanical axis seizure.

Step-by-Step Diagnostic & Recovery Procedure

1. Check servo diagnostic parameter DGN 200/204 to identify bit (OVC, OVL, HCA). 2. Disconnect motor power cable and megger test motor windings. 3. Verify DC bus voltage on servo amplifier. 4. Inspect ball screw for mechanical jamming.

Fanuc Alarm 910 SRAM Parity Error (Low/High Byte)
Alarm

Battery-backed static RAM has experienced bit corruption or battery voltage dropped below critical retention threshold.

Potential Root Causes

Backup memory lithium battery depleted, electrical power surge, corrupted system parameters, defective main CPU board.

Step-by-Step Diagnostic & Recovery Procedure

1. Replace 3V lithium battery while control is powered on. 2. Restore complete SRAM backup from CF card / USB boot menu. 3. If parity alarm persists, reseat SRAM DIMM or replace CPU motherboard.

Haas Alarm 102 Servos Off
Alarm

Servos have been turned off by E-stop, door open safety interlock, fault condition, or timeout.

Potential Root Causes

Emergency stop button depressed, enclosure door interlock tripped, servo amplifier overheat, low pneumatic pressure.

Step-by-Step Diagnostic & Recovery Procedure

1. Clear Emergency Stop button by pulling out. 2. Ensure all enclosure doors are fully closed. 3. Check main air regulator gauge (must read > 85 PSI / 5.9 bar). 4. Press Reset key twice to re-engage servo amplifiers.

Haas Alarm 107 Emergency Stop
Alarm

Emergency Stop switch on operator pendant or remote pendant has been actuated.

Potential Root Causes

Operator pressed E-stop, broken pendant cable wire, faulty E-stop contact block.

Step-by-Step Diagnostic & Recovery Procedure

1. Turn E-stop button clockwise to release. 2. Inspect wiring harness if alarm cannot be cleared. 3. Verify status of discrete I/O diagnostic bit for E-stop input.

Haas Alarm 993 Linear Guide Lubrication Fault
Alarm

Automatic grease or oil lubrication system failed to build pressure or reservoir level is below minimum threshold.

Potential Root Causes

Empty lube reservoir, air bubble in lube lines, ruptured nylon lube hose, clogged lube injector block.

Step-by-Step Diagnostic & Recovery Procedure

1. Refill lubrication reservoir with specified mobile SHC 007 or ISO VG 68 way lube. 2. Prime lubrication pump using diagnostic purge cycle. 3. Inspect way lube lines along X, Y, Z axes for physical damage.

Mazak Alarm 201 Spindle Controller Malfunction
Alarm

Communication failure or internal fault within the Mazak Mitsubishi spindle drive inverter.

Potential Root Causes

Blown spindle drive fuse, incoming 3-phase line drop, excessive spindle deceleration regeneration, motor cooling fan failed.

Step-by-Step Diagnostic & Recovery Procedure

1. Inspect 7-segment LED display on Mitsubishi MDS spindle amplifier. 2. Verify 200-220V 3-phase supply balance. 3. Clear chips from spindle motor ventilation intake.

Siemens Alarm 25201 Axis Drive Fault (Servo Error)
Alarm

The SINAMICS S120 motor drive has signalled a drive fault to the 840D/ONE NCU.

Potential Root Causes

Excessive tracking error, drive power unit thermal trip, resolver/DRIVE-CLiQ feedback failure.

Step-by-Step Diagnostic & Recovery Procedure

1. Open SINUMERIK Alarm Log and check SINAMICS drive fault code (F07xxx). 2. Inspect DRIVE-CLiQ cable connection. 3. Check motor thermal sensor resistance.

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