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FANUC Controller
Program/G-code · Intermediate · 15-30 minutes
Fanuc Alarm 218 - NOT FOUND P/Q COMMAND
Alarm 218 occurs when the G51.2 (programmable mirror image) command is issued without the required P or Q address, or when the P/Q value is outside the acceptable range (typically 0 or 1). This is a syntax error in the part program where the coordinate axis specification for mirroring is missing or incorrect.
218
Fanuc Alarm 218 - NOT FOUND P/Q COMMAND
SYSTEM ALARM 218
Fanuc alarm 218: SYSTEM ALARM 218. This alarm indicates a fault condition detected by the Fanuc control. Refer to the alarm number and name to identify the specific system or function involved.
Root Cause Summary
Alarm 218 occurs when the G51.2 (programmable mirror image) command is issued without the required P or Q address, or when the P/Q value is outside the acceptable range (typically 0 or 1). This is a syntax error in the part program where the coordinate axis specification for mirroring is missing or incorrect.
Causes and Fixes
- 1
Display the program on the CNC screen and navigate to EDIT mode. Search for the G51.2 block that triggered the alarm using the SEARCH function.
- 2
Verify the G51.2 block contains P and/or Q address. Correct syntax examples: G51.2 P1 (mirror X-axis), G51.2 Q1 (mirror Y-axis), or G51.2 P1 Q1 (mirror both axes).
- 3
Edit the program to add the missing P or Q address. Use P0/Q0 to cancel mirror on that axis, P1/Q1 to activate mirror on that axis.
- 4
Reset the alarm using RESET button, return to memory or MDI mode, and re-run the program to verify the correction.
Call a technician if:
- ·Parameter corruption suspected
- ·Repeated alarms after program correction
- ·System parameters require modification
Prevention
- Always include both P and Q parameters in G51.2 blocks
- Use normalized unit vectors for rotation axes
- Validate G51.2 syntax in program simulation before running
Common Mistakes
- Omitting Q parameter when only P is obvious
- Using excessive decimal precision in P/Q values
- Confusing G51.2 with G51 scaling parameters
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