What causes FANUC alarm 241?

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 241?

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 241. 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 241

Fanuc 241 - Illegal command in speed control

Alarm 241 occurs when the CNC encounters a command that is not permitted during constant surface speed (G96) or spindle speed control modes. This is most commonly caused by attempting to perform threading, tapping, or rigid tapping operations while G96 (CSS) is active, or using incompatible G-codes in speed-controlled modes.

FANUCProgram/G-codeIntermediate5-30 minutes

241

Fanuc 241 - Illegal command in speed control

ILLEGAL COMMAND IN SPEED CONTROL

Root Cause Summary

Alarm 241 occurs when the CNC encounters a command that is not permitted during constant surface speed (G96) or spindle speed control modes. This is most commonly caused by attempting to perform threading, tapping, or rigid tapping operations while G96 (CSS) is active, or using incompatible G-codes in speed-controlled modes.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Review the program line where the alarm occurs and identify if G32, G76, G92, G84, G88, or G74 is being commanded.
2
Check preceding program blocks to verify if G96 (CSS mode) is currently active without being cancelled.
3
Insert G97 S____ (constant RPM mode with specific speed) before any threading or tapping cycle to cancel CSS mode.
Ensure the S value specified is appropriate for the tool and material to prevent tool breakage or poor surface finish.
4
After the threading or tapping operation completes, G96 can be reactivated if needed for subsequent turning operations.

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