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FANUC Controller
Servo/Axis · Intermediate · 5-30 minutes
Fanuc 477 - Fssb optical fiber error
Alarm 477 indicates a communication failure on the FSSB optical fiber network between the CNC control and servo amplifiers. This is typically caused by damaged fiber optic cables, contaminated or loose connectors, or failed optical transmission modules in the amplifiers or control unit.
477
Fanuc 477 - Fssb optical fiber error
FSSB OPTICAL FIBER ERROR
An FSSB (Fanuc Serial Servo Bus) error has been detected related to fssb optical fiber error. The serial bus communication between the CNC and servo amplifiers is affected.
Root Cause Summary
Alarm 477 indicates a communication failure on the FSSB optical fiber network between the CNC control and servo amplifiers. This is typically caused by damaged fiber optic cables, contaminated or loose connectors, or failed optical transmission modules in the amplifiers or control unit.
Safety
- Verify corrected program or parameters before resuming machining
Causes and Fixes
- 1
Power down the machine and visually inspect all orange fiber optic cables between CNC and amplifiers for physical damage, kinks, or pinch points.
Never look directly into fiber optic cable ends - laser light can damage eyes
- 2
Check that all fiber optic connectors are fully seated and locking tabs are engaged at both CNC and amplifier ends.
- 3
Verify fiber cables are not bent tighter than 30mm radius and are properly routed away from sharp edges and moving components.
- 4
Swap the suspected fiber cable with a known good spare and power up to test if alarm clears.
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