What causes FANUC alarm 181?

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 181?

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 181. 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 181

Fanuc 181 - Illegal command in tool measurement

Alarm 181 occurs when the control detects an invalid G-code, M-code, or parameter during a tool measurement cycle or skip signal operation. This is most commonly caused by using incompatible commands during G31 skip function, incorrect syntax in measurement macros, or attempting tool measurement operations without proper hardware/parameter configuration.

FANUCProgram/G-codeIntermediate5-30 minutes

181

Fanuc 181 - Illegal command in tool measurement

ILLEGAL COMMAND IN TOOL MEASUREMENT

Root Cause Summary

Alarm 181 occurs when the control detects an invalid G-code, M-code, or parameter during a tool measurement cycle or skip signal operation. This is most commonly caused by using incompatible commands during G31 skip function, incorrect syntax in measurement macros, or attempting tool measurement operations without proper hardware/parameter configuration.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Review the program line number shown with the alarm. Identify the active G31 or tool measurement block and the command that triggered the alarm.
2
Check for illegal commands within or immediately after G31 blocks: M06, G52, G54-G59, G68, G51, G50.1, or M-codes that affect spindle/coolant during measurement.
3
Restructure the program to execute the incompatible command before initiating G31 or after the measurement cycle is complete and cancelled with G80 or G40.
4
Verify that G31 is followed by a linear move command (G01 or G00) with appropriate feedrate and that skip signal macro variables are correctly referenced.

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