What causes FANUC alarm 243?

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 243?

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 243. 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 243

Fanuc 243 - Speed control parameter error

Alarm 243 indicates a speed control parameter error in the part program, typically triggered by invalid G-code speed commands, out-of-range spindle speeds, or improperly formatted feed rate commands. This programming alarm occurs when the control encounters speed-related values that violate parameter limits or syntax rules during program execution or verification.

FANUCProgram/G-codeIntermediate5-30 minutes

243

Fanuc 243 - Speed control parameter error

SPEED CONTROL PARAMETER ERROR

Root Cause Summary

Alarm 243 indicates a speed control parameter error in the part program, typically triggered by invalid G-code speed commands, out-of-range spindle speeds, or improperly formatted feed rate commands. This programming alarm occurs when the control encounters speed-related values that violate parameter limits or syntax rules during program execution or verification.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Identify the program line number where alarm occurred and examine the S-code command at or immediately before that line.
2
Check parameter 3741 (maximum spindle speed) and verify the S-code value does not exceed this limit. Also verify parameter 3772 for gear-specific speed limits if applicable.
3
Verify S-code format is correct (integer value only unless constant surface speed mode is active). Remove any decimal points from direct spindle speed commands.
4
If using G96 (constant surface speed), verify G97 is commanded before returning to direct RPM mode, and that the S-code contains appropriate values for each mode.

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