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SV0491 DCS: Safety I/O Error fault in Fanuc drive

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SV0491 DCS: Safety I/O Error fault in Fanuc drive Description SV0491 is a Dual Check Safety (DCS) alarm. In a DCS environment, safe signals (like Emergency Stop, Door Interlock, or Safety Speed Monitoring) are transmitted via a redundant I/O link. SV0491 indicates that the two separate checking channels (Path A and Path B) for a specific I/O signal disagree. For example, Path A says the door is "Closed" (Logic 1), but Path B says the door is "Open" (Logic 0). The machine defaults to the safest state (Stop) and throws this alarm. Cause Bad Safety Switch: A dual-channel tongue switch on a door has one broken contact. One side closes, the other stays open. Loose Wire: One of the two wires in the safety pair is loose at the terminal block (X11/X12 signals). I/O Module Failure: The Safety I/O board (or con...
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SV0406 Reference Position Return Error fault in Fanuc drive

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SV0406 Reference Position Return Error fault in Fanuc drive Description SV0406 differs from SV0405. While SV0405 means "I failed to find the reference," SV0406 means "I found the reference mark, but it wasn't where I expected it to be." During the Homing cycle, the machine hits the deceleration dog, slows down, and looks for the grid pulse. If the distance traveled between the dog switch and the grid pulse varies significantly from the previous setting, the CNC flags this as a reliability risk. It thinks the switch moved or the motor skipped a pole. Cause Dirty Switch: The deceleration dog switch is sticky. It released late, changing the distance calculation. Grid Mask: The switch is placed too close to the encoder's Z-pulse. This is the "One Revolution" issue. If the switch releases exactly on top of the Z-pulse...
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SV0308 APC Alarm: Battery Low 2 (External) fault in Fanuc drive

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SV0308 APC Alarm: Battery Low 2 (External) fault in Fanuc drive Description SV0308 is the counterpart to SV0307. While SV0307 usually refers to the battery plugged directly into the drive (CX5X), SV0308 often refers to the battery voltage of a "Separate Detector" (Scale) or an external battery box that feeds multiple encoders. This is common on large gantry machines where a central D-cell battery pack powers 4-6 motors. It is a pre-warning; position data is still safe. Cause Dead Battery Box: The large alkaline D-cells in the external black Fanuc battery case are dead. Cable Break: The cable running from the battery box to the servo amplifier has a broken wire. Connector Corrosion: The battery box terminals are corroded (leaking batteries). Solution ...
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SV0419 Spindle Position Error (Rigid Tap) fault in Fanuc drive

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SV0419 Spindle Position Error (Rigid Tap) fault in Fanuc drive Description SV0419 is a specific servo alarm that occurs during Rigid Tapping . During tapping, the Z-axis servo is electronically geared to the Spindle. The servo must follow the spindle's exact rotation to cut the thread pitch. SV0419 triggers if the "Following Error" between the Spindle (Master) and the Z-axis (Slave) becomes too large. The Z-axis is effectively saying, "The spindle is spinning, and I can't keep up with the thread pitch." Cause Spindle Encoder: The position feedback from the spindle is erratic or noisy. Servo Tuning: The gain settings for the Z-axis are too "soft," causing it to lag. Mechanical Bind: The tap is dull or the hole is packed with chips, causing physical drag on the Z-axis that the motor ca...
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SP9052 (Alarm 52) ITP Signal Error (Synchronization) fault in Fanuc drive

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SP9052 (Alarm 52) ITP Signal Error (Synchronization) fault in Fanuc drive Description SP9052 (Alarm 52) is a synchronization clock error between the CNC and the Spindle Amplifier. "ITP" stands for Interpolation Time Period. In high-speed contouring or C-axis mode, the CNC sends position commands at precise time intervals. If the Spindle Drive receives these packets out of sync with its own internal clock, Alarm 52 is generated. It implies the two CPUs (CNC and Drive) have drifted apart in time. Cause I/O Link Cable: The serial cable carrying the data is picking up noise, delaying the packets. CNC CPU Load: The CNC main processor is overloaded (too many background scripts or complex look-ahead), causing jitter in the signal transmission. Drive Logic: The Spindle Drive control board's oscillator is drifting. ...
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SV0452 Pulse Coder: Noise Alarm fault in Fanuc drive

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SV0452 Pulse Coder: Noise Alarm fault in Fanuc drive Description SV0452 is a specific alarm generated by the alpha-series Pulse Coder when it detects high-frequency interference. The encoder has internal logic that monitors the stability of the signal. If it sees rapid, impossible fluctuations in the signal frequency (jitter) that exceed the laws of physics for motor acceleration, it flags it as "Noise" rather than a valid move. Cause Bad Shielding: The feedback cable shield is not grounded or is broken. Ground Loops: The motor frame and the electrical cabinet are at different ground potentials. Cable Routing: Running the feedback cable in the same duct as a plasma cutter lead or EDM power cable. Connectors: Liquid (coolant/oil) inside the connector acting as a conductor for noise....
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SP9058 (Alarm 58) Spindle Converter Overload fault in Fanuc drive

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SP9058 (Alarm 58) Spindle Converter Overload fault in Fanuc drive Description SP9058 (Alarm 58) is similar to SV0431 but reported by the Spindle Drive. It indicates that the temperature of the main DC Link Converter (rectifier section) or the regenerative braking resistor has exceeded the limit. This often happens on machines where the Spindle Drive handles the regeneration locally rather than passing it back to a shared PSM. Cause Heavy Braking: Repeatedly starting and stopping a heavy chuck (e.g., lathe work) causes massive heat in the regen resistor. Heatsink Clog: The cooling fins on the back of the spindle drive are blocked. Fan Failure: The external cooling fan (radiator fan) is dead. Solution Duty Cycle: Incre...
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