What causes FANUC alarm 274?

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 274?

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 274. 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 274

Fanuc 274 - Illegal command in rigid tapping

Alarm 274 occurs when the CNC detects a prohibited G-code or M-code command during a rigid tapping cycle (G84 or G74). The control cannot process certain operations while synchronized spindle-axis motion is active, such as feedrate overrides, axis moves, or incompatible modal commands that would break synchronization between spindle rotation and Z-axis position.

FANUCProgram/G-codeIntermediate5-30 minutes

274

Fanuc 274 - Illegal command in rigid tapping

ILLEGAL COMMAND IN RIGID TAPPING

Root Cause Summary

Alarm 274 occurs when the CNC detects a prohibited G-code or M-code command during a rigid tapping cycle (G84 or G74). The control cannot process certain operations while synchronized spindle-axis motion is active, such as feedrate overrides, axis moves, or incompatible modal commands that would break synchronization between spindle rotation and Z-axis position.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Review the program line where alarm occurred. Look for G84 or G74 and identify any G-codes in the same block or immediately following lines.
2
Remove or relocate prohibited commands such as G04, G10, G28, G29, G30, G31, G53, G65, or G66 that appear during the tapping cycle.
3
Ensure the rigid tap block contains only G84/G74, X, Y, Z, R, Q, P, F parameters. Use standard format: G84 Z-depth R-return F-feedrate S-speed M29 (or M3/M4).
4
Verify G80 (cancel cycle) or G00/G01 is programmed after the rigid tap operation completes to properly exit the canned cycle mode.

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