What causes FANUC alarm 487?

FSSB optical fiber cable damaged, dirty, or disconnected. Servo amplifier incompatible with the configured FSSB parameters. Parameter mismatch between configured and detected FSSB axis/amplifier count. Power cycle needed after FSSB parameter change. Servo amplifier hardware failure on the FSSB chain.

How do I fix FANUC alarm 487?

1. Check all FSSB optical fiber cables for damage, contamination, or loose connections. 2. Review FSSB-related parameters (1023, 1936 series) for correct axis-to-amplifier mapping. 3. Count the servo amplifiers in the chain and verify the count matches the parameter setting. 4. Power cycle completely — some FSSB errors only clear on a full power cycle. 5. Check individual amplifier fault codes if a specific amplifier is causing the issue.

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FANUC Controller

Spindle · Intermediate · 5-30 minutes

Alarm 487

Fanuc 487 - Fssb spindle mismatch

Alarm 487 indicates a mismatch between the spindle configuration stored in the CNC parameters and the actual spindle amplifier detected on the FSSB (Fanuc Serial Servo Bus). This typically occurs after amplifier replacement, parameter changes, or when the wrong amplifier model is connected to the spindle axis position on the FSSB network.

FANUCSpindleIntermediate5-30 minutes

487

Fanuc 487 - Fssb spindle mismatch

FSSB SPINDLE MISMATCH

Root Cause Summary

Alarm 487 indicates a mismatch between the spindle configuration stored in the CNC parameters and the actual spindle amplifier detected on the FSSB (Fanuc Serial Servo Bus). This typically occurs after amplifier replacement, parameter changes, or when the wrong amplifier model is connected to the spindle axis position on the FSSB network.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Access parameter 4131 and verify the spindle amplifier type code matches the physical amplifier model installed (check amplifier nameplate for model number).
2
Check parameter 4030#0 and related spindle serial number parameters - if amplifier was replaced, these may need to be cleared or updated to match new amplifier.
Set parameter write enable (PWE) to 1 before making changes - incorrect parameters can damage equipment
3
Power cycle the complete system (CNC and all amplifiers) after parameter corrections to force FSSB re-initialization and device detection.
4
If alarm persists, perform FSSB device configuration reset by setting parameter 8151 to match the actual connected devices, then power cycle again.

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