What causes FANUC alarm 399?

Part program contains an illegal G-code or M-code combination for this alarm type. Missing or incorrect address word in the program block. Axis or parameter value out of range for the commanded function. Required option not enabled on this CNC for the commanded function. Conflict between active modal states and the commanded function.

How do I fix FANUC alarm 399?

1. Note the block number shown on the alarm screen and locate that block in the program. 2. Review the command in that block against the Fanuc programming manual for alarm 399. 3. Check for missing address words, incorrect values, or conflicting G-code combinations. 4. Verify any required CNC options are enabled if using advanced functions. 5. Correct the program and verify the fix before restarting machining.

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FANUC Controller

Program/G-code · Intermediate · 5-30 minutes

Alarm 399

Fanuc 399 - Smooth interpolation not ready

Alarm 399 occurs when smooth interpolation (G05.1 Q1) is commanded but the required conditions are not met. This typically happens when AI contour control or nano smoothing features are enabled without proper parameter settings, incorrect option configuration, or when the control software version doesn't support the commanded smoothing mode.

FANUCProgram/G-codeIntermediate5-30 minutes

399

Fanuc 399 - Smooth interpolation not ready

SMOOTH INTERPOLATION NOT READY

Root Cause Summary

Alarm 399 occurs when smooth interpolation (G05.1 Q1) is commanded but the required conditions are not met. This typically happens when AI contour control or nano smoothing features are enabled without proper parameter settings, incorrect option configuration, or when the control software version doesn't support the commanded smoothing mode.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Check if AI contour control/nano smoothing option is installed by reviewing the control's option list (press SYSTEM > PARAMETER > check bit settings for smooth interpolation options).
2
Verify parameter 19650 (AI advanced preview control) and related smooth interpolation parameters (19600-19699 series) are properly configured per Fanuc documentation.
Parameter changes require control restart and may affect machining performance.
3
Confirm parameter 1610#6 (AI contour control enable) is set to 1 if using AI nano smoothing features.
4
If option is not installed, remove G05.1 Q1 commands from program or contact Fanuc distributor for option enablement.

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