click2electro

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...

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...

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 ...

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...

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. ...

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....

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...

SV0412 Excessive Error (Stopped/Drift) fault in Fanuc drive Description SV0412 is a variation of SV0410. While SV0410 is "Excess Error," SV0412 often points specifically to "Drift." It means the axis is moving when it shouldn't be, or the error is accumulating very slowly while stopped. It suggests that the integral term in the servo loop is winding up because the motor is applying torque but the position isn't correcting. Cause Parameter Tuning: The velocity loop gain is too high, causing oscillation (hunting) while stopped. Unbalanced Load: On a vertical axis, the counterbalance is slightly off, so the motor is constantly fighting gravity, causing the error integrator to creep up. Noise: Low-level noise on the analog command (if using analog drives) or encoder signal causing the drive to th...

SV1069 FSSB: CRC Error (Slave) fault in Fanuc drive Description SV1069 is the Slave-side version of the FSSB Optical Error. It means the servo amplifier (Slave) received a data packet from the CNC (Master) but the checksum (CRC) was invalid. The data was corrupted in transit from the CNC to the Drive. This is different from the Master-side error which indicates corruption on the return path. Cause Dirty Input Port: The COP10B (Input) port on the drive is dusty. Cable Bend: The fiber optic cable leading into this drive is bent too sharply. Previous Drive: The previous drive in the chain (which transmits to this one) has a failing optical transmitter. Solution Trace Source: The error is happening AT the drive, but th...

SV0426 Disconnect Alarm (Separate Detector) fault in Fanuc drive Description SV0426 is the specific "Disconnect" alarm for systems using a Separate Detector (External Scale) interface unit. It differs from SV0447 (which is a general hard disconnect) by pointing specifically to the 5V power supply or differential signal loss at the interface card level. It implies the interface unit sees the scale, but the signals are flatlining. Cause Unplugged Scale: The scale connector is loose. Broken Wire: The 5V supply wire in the scale cable is broken. Interface Card: The separate detector interface card (on the CNC or Drive) has a blown fuse for the scale power. Solution Check LEDs: Look at the Scale Interface Unit (...

SV0494 DCS: VRDY ON (Safety Mismatch) fault in Fanuc drive Description SV0494 is a critical alarm specific to machines equipped with Dual Check Safety (DCS) . DCS is a redundant safety system where the CNC monitors safety signals through two independent channels (Path A and Path B). SV0494 occurs when the redundant check for the "Velocity Ready" (VRDY) signal fails. The CNC commanded the Safe Torque Off (STO) function to engage (shutting down power to the motor), but one of the two safety channels reported that the drive was still active. This is a "Safety Cross-Check" failure. Cause Welded Contactor: The Safety Contactor (MCC) has welded contacts. One channel sees it closed, while the software commanded it open. STO Timing: The "Safe Torque Off" wiring to the drive (STO1 and STO2 signals) did not drop out simultaneously...

SP9051 (Alarm 51) Spindle DC Link Undervoltage fault in Fanuc drive Description SP9051 (Alarm 51) is the Spindle Amplifier's specific version of a DC Link Undervoltage. While the PSM usually manages the bus, the Spindle drive monitors the DC level locally. If the voltage drops below a critical threshold (e.g., 200V DC) while the spindle is idle or running, Alarm 51 triggers. It differs from Input Undervoltage (Alarm 10) as it focuses on the stored DC energy available for the inverter. Cause Momentary Power Loss: A micro-cut in the facility power supply that wasn't long enough to shut off the CNC but was deep enough to drain the capacitors. Loose Bus Bars: High resistance on the DC link connection between PSM and Spindle Drive. Charging Circuit: The PSM failed to fully pre-charge the bus. ...

SV0363 Clock Error (Pulsecoder) fault in Fanuc drive Description SV0363 is a hardware health alarm for the Built-in Absolute Pulse Coder. The encoder contains an internal clock oscillator (crystal) that synchronizes the position counting and serial data transmission. If this internal clock frequency drifts or stops due to component failure, the drive detects that the timing of the incoming data packets is erratic and triggers SV0363. Cause Hardware Failure: The crystal oscillator inside the encoder cap has shattered due to mechanical shock or vibration. Thermal Drift: Extreme heat has caused the oscillator to drift outside of its frequency tolerance. Noise: Extremely high-frequency EMI can sometimes disrupt the clock signal line, though this is rare. Solution ...

SP9013 (Alarm 13) Spindle CPU Data Memory Error fault in Fanuc drive Description SP9013 (Alarm 13) is a "Death Screen" for the Spindle Amplifier. It indicates that the internal CPU on the spindle drive's control board attempted to read/write to its own RAM or EEPROM and failed. This is a checksum error or a hardware read failure. The drive's "Brain" is effectively corrupted and cannot run the software required to control the motor. Cause Board Aging: The solder joints on the memory chips have cracked due to thermal cycling over 15-20 years. Power Surge: A voltage spike entered the 24V control power line and damaged the logic chips. Contamination: Conductive dust or coolant mist has bridged pins on the control PCB. Solution ...

SV0459 Hi-Speed 1-Rev Signal (Sep. Detector) fault in Fanuc drive Description SV0459 is the "External Scale" version of the 1-Rev Signal Error. It appears when using a linear scale or external rotary encoder for positioning. The CNC needs to see the "Reference Mark" (Z-pulse) from the scale to establish the absolute grid. SV0459 triggers if the reading head passes the reference mark location but fails to detect the pulse, or detects it at an improper width/interval. Cause Dirty Scale: The specific location on the glass scale where the reference mark is etched is dirty or scratched. Alignment: The read-head is slightly twisted (yaw/pitch angle), making it unable to focus on the fine reference mark grating. Speed: Attempting to reference the machine at a speed faster than the scale can process the Z-pul...

SV0415 Motion Range Exceeded (Soft Shift) fault in Fanuc drive Description SV0415 is a sophisticated soft-limit alarm. Unlike SV0403 (which triggers when you hit a static wall), SV0415 triggers based on a calculation of "Excess Shift." It determines that the commanded move combined with the current error and velocity would push the axis beyond the safe movable range or "stroke limit check" during high-speed operation. It essentially predicts a crash into the soft limit before it physically happens. Cause Erratic Speed: A sudden spike in velocity command causing the "stopping distance" calculation to exceed the remaining travel distance. Parameter Setting: The "Excess Shift" threshold parameter (1829 or similar) is set too tight for the rapid rate of the machine. Noise: Noise on the...

SP9037 (Alarm 37) Speed Detector Parameter Error fault in Fanuc drive Description SP9037 (Alarm 37) is a configuration alarm on the Spindle Drive. It indicates a conflict in the parameter settings regarding the speed feedback device. The drive has parameters defining the number of pulses per revolution and the number of gear teeth (if using a magnetic sensor). If the drive detects signals that contradict these settings (e.g., receiving 128 pulses when it expects 256), Alarm 37 prevents rotation. Cause Parameter Entry: Someone manually changed the spindle parameters (4000 series) and entered the wrong value for the sensor type. Gear Shift: The machine shifted gears (High/Low), but the proximity switch confirming the gear shift failed. The drive is using "Low Gear" parameters while the spindle is mechanically in "High Gear." ...

SV0381 Abnormal Phase (Separate Detector) fault in Fanuc drive Description SV0381 is a startup phase check for external linear scales. When the system powers on, it reads the immediate state of the A and B phase signals. If both signals are high or low in a way that suggests a broken wire or short circuit (e.g., A and /A are both High), SV0381 is triggered immediately. It differs from SV0384 (Running Phase Error) as this is a static electrical check. Cause Wiring Short: The cable has been crushed, shorting the A+ wire to the A- wire. Unplugged: The connector is physically disconnected. Wrong Pinout: A new cable was made, but the soldering pinout does not match the Fanuc standard for that specific feedback card. Solution ...

SV0464 FSSB CRC Error (Optical Noise) fault in Fanuc drive Description SV0464 is a specific Cyclic Redundancy Check (CRC) error for the FSSB optical ring. It indicates that data is flowing through the fiber optic cables, but the integrity of the data is compromised. Bit errors are occurring during transmission. This is typically an "Analog" failure of the optical system—the light is getting through, but it is too dim or too distorted to be read accurately. Cause Kinked Cable: Fiber optic cables have a minimum bend radius. If a cable is zip-tied too tightly or bent at a sharp 90-degree angle, the light refracts out of the core, weakening the signal. Dust on Lens: The optical transmitter/receiver ports on the drive are covered in dust. Loose Plug: The connector is not fully clicked into the socket. ...

SP9024 (Alarm 24) Serial Transfer Error (Spindle) fault in Fanuc drive Description SP9024 (Alarm 24) indicates a breakdown in the serial communication specifically between the CNC and the Spindle Amplifier. Unlike FSSB (Optical), older or non-optical spindle drives use an electrical serial cable. This alarm means the "Heartbeat" signal from the CNC to the Spindle drive has stopped. The spindle drive shuts down because it is no longer receiving commands. Cause Cable Failure: The electrical serial cable (often a customized Honda connector cable) is broken or has a loose shield. CNC Lockup: The Main CPU of the CNC has frozen or crashed, stopping the data stream. I/O Link Module: If the spindle is connected via I/O Link, the interface module may have failed. Soluti...