What causes FANUC alarm 250?

Peripheral system (hydraulic, coolant, auxiliary) component fault or sensor indicating an out-of-limit condition. PMC input signal from the affected peripheral device not in the expected state. Fluid level, pressure, or temperature outside acceptable limits. Mechanical fault in the peripheral system mechanism. Wiring or sensor fault on the peripheral system I/O.

How do I fix FANUC alarm 250?

1. Identify the specific peripheral system indicated by the alarm name. 2. Check the fluid level, pressure, and temperature for the relevant system. 3. Inspect the relevant mechanism for mechanical faults or obstructions. 4. Check the PMC input signals for the peripheral system in the Fanuc PMC monitor. 5. Consult the machine tool builder documentation for alarm 250 specific remedy.

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FANUC Controller

Probing · Intermediate · 15-30 minutes

Alarm 250

Fanuc Alarm 250 - Touch Probe Error

Fanuc Alarm 250 occurs when the part program contains a Z-axis movement command in the same program block as the M06 tool change command. This violates the standard tool change protocol where M06 must be executed independently to ensure safe and proper tool changing sequence.

FANUCProbingIntermediate15-30 minutes

250

Fanuc Alarm 250 - Touch Probe Error

Probe Alarm

Root Cause Summary

Fanuc Alarm 250 occurs when the part program contains a Z-axis movement command in the same program block as the M06 tool change command. This violates the standard tool change protocol where M06 must be executed independently to ensure safe and proper tool changing sequence.

Safety

Probing disabled

Causes and Fixes

1
Review the program block that triggered the alarm. Look for any block containing M06 with G00, G01, G43, or any Z-axis coordinate in the same line.
2
Separate the Z-axis positioning move into a previous block. Place M06 (with T-code if required) in its own dedicated block. Example: Change 'G00 Z100. M06 T02' to two blocks: 'G00 Z100.' then 'M06 T02'.
3
Check parameter 5010 (Tool change position parameter) and 5011-5013 (ATC position coordinates). Verify the machine is programmed to move to tool change position automatically via parameters, not via explicit Z commands.
4
Reset the alarm, return to safe position, and restart the program from the corrected block. Verify tool change sequence completes without alarm.
Always ensure spindle is stopped and clear of workpiece before executing tool change commands.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter changes required beyond programming
·ATC mechanical issues discovered
·Persistent alarms after program corrections

Prevention

Always separate Z-axis moves and M06 commands into different NC blocks
Configure CAM post-processor with proper FANUC tool change templates
Use standard tool change sequences: G00 Z[safe] then M06 T[tool]

Common Mistakes

Combining rapid Z moves with M06 in single block
Using generic post-processors not optimized for FANUC
Modifying working programs without understanding tool change sequence requirements

Related Alarms

078 079 090 091

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