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FANUC Controller
Program/G-code · Basic · 5-15 minutes
Fanuc Alarm 081 - OFFSET NUMBER NOT FOUND IN G37
Fanuc Alarm 081 occurs when a G37 (automatic tool length measurement) command is executed without a valid H-code offset number in the same block or modal state. The control requires an H-code to specify which tool offset register will store the measured tool length value. This is a programming error rather than a machine or parameter issue.
081
Fanuc Alarm 081 - OFFSET NUMBER NOT FOUND IN G37
Arc Center Error
Fanuc program alarm 081: Arc Center Error. The part program contains an error or illegal condition that the Fanuc control cannot execute. Correct the program to clear this alarm.
Root Cause Summary
Fanuc Alarm 081 occurs when a G37 (automatic tool length measurement) command is executed without a valid H-code offset number in the same block or modal state. The control requires an H-code to specify which tool offset register will store the measured tool length value. This is a programming error rather than a machine or parameter issue.
Safety
- Verify arc before running
- Verify arc toolpath before executing program
- Ensure the machine is in a safe state before running any diagnostic tests. Stop the spindle and disable the feed hold.
- Be aware of potential collision hazards during dry runs. Keep a hand on the feed hold button.
- If adjusting machine parameters, consult the machine's documentation and proceed with caution. Incorrect parameter settings can damage the machine.
- Electrical Hazard: Power must be disconnected before working on any internal components. Only qualified personnel should perform electrical troubleshooting.
- Mechanical Hazard: Ensure all guards and safety devices are in place before operating the machine.
- Verify the arc and program before running to prevent machine damage or injury.
- Always ensure the machine is powered down and locked out during troubleshooting.
Causes and Fixes
- 1
Review the program block containing G37. Verify that an H-code is specified in the format: G37 Z__ H__ (example: G37 Z-100.0 H01). The H-code must be in the same block as G37.
- 2
Check the offset range capacity via OFFSET > GEOM screen. Verify the H-code number specified does not exceed the maximum tool offset number available (typically limited by parameter 13210 or 13211 for geometry offsets).
- 3
Edit the program to include the correct H-code: Example format - G91 G37 Z-100.0 H01; where H01 specifies offset #1 will store the measured value.
- 4
Reset the alarm, return to program start or safe position, and re-execute the corrected G37 block with proper H-code specification.
Ensure the tool is positioned safely above the measurement surface before executing G37 to prevent tool or probe damage.
Call a technician if:
- ·Parameter changes don't resolve the issue
- ·Alarm persists across multiple different arc programs
- ·Suspected encoder or feedback system problems
Prevention
- Always verify arc geometry with CAM software before posting
- Use consistent arc programming format throughout programs
- Regularly backup and verify critical parameters like 3410 and 3405
Common Mistakes
- Mixing R and I,J,K formats in same block
- Programming arcs with end points exactly 2R apart (creates ambiguous center)
- Forgetting to account for work coordinate transformations in arc calculations
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