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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 ...