What causes FANUC alarm 186?

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 186?

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 186. 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 186

Fanuc 186 - Cylindrical interpolation illegal axis

Alarm 186 occurs when the cylindrical interpolation command (G07.1) is programmed with axis combinations that are not permitted or when required axes are missing. The control expects a specific rotary axis paired with two linear axes where one linear axis represents the radius vector, and the axis configuration does not match the parameter settings or geometric requirements for cylindrical interpolation.

FANUCProgram/G-codeIntermediate5-30 minutes

186

Fanuc 186 - Cylindrical interpolation illegal axis

CYLINDRICAL INTERPOLATION ILLEGAL AXIS

Root Cause Summary

Alarm 186 occurs when the cylindrical interpolation command (G07.1) is programmed with axis combinations that are not permitted or when required axes are missing. The control expects a specific rotary axis paired with two linear axes where one linear axis represents the radius vector, and the axis configuration does not match the parameter settings or geometric requirements for cylindrical interpolation.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Review the G07.1 command line in your program and verify the axis designations (e.g., G07.1 C_ _ _). Typical format is G07.1 followed by rotary axis designation and coordinate system.
2
Check parameter 1022 to verify which axis is designated as the rotary axis for cylindrical interpolation. Ensure your program uses the same axis letter.
3
Verify that the two linear axes specified form a valid plane perpendicular to the rotary axis (e.g., if C is rotary around Z, then X and Z should be specified, not Y and Z).
4
Correct the G07.1 command to match the machine configuration. Example: G07.1 C for C-axis cylindrical interpolation, then verify subsequent motion commands use valid axis combinations.
Test program in single block mode after corrections to verify proper axis movement.

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