System: FANUC Series 31i-MODEL B
Alarms: FANUC PW0012, PW0013, SV1067, SV1068, SV0484, SV0496, SP1978, EX1019, EX1028

Alarm Descriptions:
    •    PW0012: User I/O interface error detected (DCS PMC)
    •    PW0013: User I/O interface error detected (PMC)
    •    SV1067: FSSB: Configuration error (software)
    •    SV1068: Repeated detection of safety alarm
    •    SV0484 (X/Y/Z): Safety function error (servo DSP)
    •    SV0496 (X/Y/Z): Invalid axis data (CNC)
    •    SP1978 (S): Serial spindle communication error
    •    EX1019: Spindle abnormality
    •    EX1028: Lubrication oil level low (centralized lubrication system)


Observation:
We inspected the status of each amplifier inside the electrical cabinet.


Analysis:
We found that the XYZ amplifiers are showing the alarm code “U”. If the amplifier displays the letter L or U, it is very likely an amplifier fault. The following is the explanation for this amplifier alarm code:

FANUC Servo Amplifier Module Alarm – Detailed Explanation
Alarm Code “U”
    1.    Content:
FSSB communication abnormality in the inverter (COP10B)
    2.    Cause and Troubleshooting:
    •    (a) Replace the fiber optic cable (COP10B) between the CNC and the nearest SVM that is showing “U” (e.g., between UNIT2 and UNIT3 if shown in the diagram).
    •    (b) Replace the nearest SVM showing “U” to the CNC (e.g., UNIT3).
    •    (c) Replace the SVM on the COP10B side of the SVM showing “U” (e.g., UNIT2).
    •    (d) Replace the CNC’s servo card.


Based on the analysis, the fault is likely with the spindle amplifier or X/Y axis amplifier.

Key Checkpoints:
    •    FSSB fiber optic communication
    •    Servo amplifier side panels — try re-seating the connectors, as poor contact may be the issue.
    •    If re-seating doesn’t help, try replacing the side panel of the amplifier for testing.


Next Steps if Side Panel Replacement Fails:
In the alarm images, the X, Y, and Z amplifiers all show “U”. According to the alarm code explanation, you should replace the nearest SVM showing “U” to the CNC. The above case is for reference only. When encountering similar alarms in the future, try replacing the amplifier side panel first.