What causes FANUC alarm 396?

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 396?

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 396. 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 396

Fanuc 396 - Smooth interpolation data error

Alarm 396 occurs when the smooth interpolation (AI/Nano smoothing) function encounters invalid programming data or parameter conflicts. This typically happens when G05.1 Q1 mode is active but the programmed moves contain incompatible commands, sharp direction changes, or geometry that violates smoothing constraints.

FANUCProgram/G-codeIntermediate5-30 minutes

396

Fanuc 396 - Smooth interpolation data error

SMOOTH INTERPOLATION DATA ERROR

Root Cause Summary

Alarm 396 occurs when the smooth interpolation (AI/Nano smoothing) function encounters invalid programming data or parameter conflicts. This typically happens when G05.1 Q1 mode is active but the programmed moves contain incompatible commands, sharp direction changes, or geometry that violates smoothing constraints.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Locate the N-block number displayed with the alarm in the program and review the programmed moves in that section.
2
Check if G05.1 Q1 is active and verify no G00 rapid moves, G02/G03 arcs with extreme radius changes, or coordinate system changes (G54-G59) exist within the smoothing section.
3
Verify tool radius compensation (G41/G42) is not being turned on or off during smooth interpolation—activate compensation before G05.1 Q1 and deactivate after G05.1 Q0.
4
If mixed move types exist, separate them into distinct sections with G05.1 Q0 to disable smoothing, execute the problematic move, then re-enable with G05.1 Q1.

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