What causes FANUC alarm 256?

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 256?

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 256. 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 256

Fanuc 256 - Tool life management not ready

Alarm 256 occurs when a T-code (tool call) is executed before the tool life management system is properly initialized or when tool group data is missing/corrupted. This typically happens when tool life management parameters are enabled but the control hasn't registered the tools in a group, or the tool offset number doesn't correspond to a registered tool group.

FANUCProgram/G-codeIntermediate5-30 minutes

256

Fanuc 256 - Tool life management not ready

TOOL LIFE MANAGEMENT NOT READY

Root Cause Summary

Alarm 256 occurs when a T-code (tool call) is executed before the tool life management system is properly initialized or when tool group data is missing/corrupted. This typically happens when tool life management parameters are enabled but the control hasn't registered the tools in a group, or the tool offset number doesn't correspond to a registered tool group.

Safety

Verify corrected program or parameters before resuming machining

Causes and Fixes

1
Access the Tool Life Management screen on the control (typically OFFSET/SETTING button, then select TOOL LIFE MANAGEMENT or similar menu).
2
Verify that tool groups are defined and that the specific tool number being called in the program (check the T-code at alarm line) is registered in a tool group.
3
If the tool is missing, add it to an appropriate tool group with correct tool number, H-offset number, and life count values.
4
Reset the alarm, return to program start or the appropriate sequence number, and restart the program in memory mode to verify the fix.

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