SV0460 FSSB Disconnect fault in Fanuc drive

SV0460 FSSB Disconnect fault in Fanuc drive

Description

SV0460 is a communication breakdown alarm. Unlike SV0462/463 (which are transmission errors), SV0460 means the Fanuc Serial Servo Bus (FSSB) connection was established successfully at startup, but was *completely broken* during operation. The CNC essentially says, "I was talking to the drives, and suddenly they all disappeared." This stops all axes immediately.

Cause

• Power Loss at Drive: The most common cause is the control power (24V) to the servo amplifiers being cut off while the CNC remained on. (e.g., A loose 24V wire or a tripped circuit breaker for the cabinet power supply).
• Cable Pull-out: A fiber optic cable was physically yanked out of the port due to vibration or poor routing.
• Drive Death: If the first drive in the chain suffers a catastrophic power supply failure, it goes dark, breaking the optical ring for everyone downstream.

Solution

1. Check 24V Supply: Monitor the 24VDC supply to the amplifiers. Does it drop out when a solenoid fires?
2. Check Optical Cables: Ensure the optical cables have strain relief and aren't pulled tight against the connectors.
3. Isolate: If the alarm happens constantly, bypass drives one by one (if possible) to identify if a specific amplifier is shutting down spontaneously.