What causes FANUC alarm 146?

Cutter compensation (G41 or G42) is still active when trying to enter or exit polar coordinate interpolation mode with G12.1 or G13.1. An illegal G-code such as G02 or G03 circular interpolation was programmed directly in polar coordinate interpolation mode without proper setup. G12.1 or G13.1 was commanded while a G-code from a group that conflicts with polar coordinate interpolation was still active. Canned cycle G-codes or other modal G-codes incompatible with polar coordinate interpolation were called while G12.1 was active. Programmer forgot to cancel cutter comp with G40 before the G13.1 cancel block, causing the control to reject the mode change.

How do I fix FANUC alarm 146?

1. Open the part program and locate the G12.1 and G13.1 blocks. Check that G40 is active before both the G12.1 start block and the G13.1 cancel block, not G41 or G42. 2. Scan all G-code blocks between G12.1 and G13.1 and remove or replace any G-codes that are not supported in polar coordinate interpolation mode, such as canned cycles or conflicting group codes. 3. Verify that cutter compensation is fully canceled with G40 before entering polar coordinate interpolation. Add a G40 block on the line immediately before G12.1 if it is missing. 4. Check the Fanuc parameter settings or programming manual for your specific control model to confirm which G-codes are permitted inside polar coordinate interpolation mode, as this can vary by software version. 5. After making corrections, run the program in single block mode from the beginning to step through the polar coordinate section and confirm no further alarms trigger before running at full speed.

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FANUC Controller

Program/G-code · Intermediate · 15-30 minutes

Alarm 146

Fanuc Alarm 146 - ILLEGAL USE OF G-CODE

Alarm 146 occurs when attempting to enter or exit polar coordinate interpolation mode (G12.1/G13.1) without G40 (cutter compensation cancel) active, or when an incompatible G-code is commanded during polar coordinate interpolation. The control enforces strict modal group restrictions to prevent calculation errors in the polar transformation.

FANUCProgram/G-codeIntermediate15-30 minutes

146

Fanuc Alarm 146 - ILLEGAL USE OF G-CODE

PROGRAM ALARM 146

Root Cause Summary

Alarm 146 occurs when attempting to enter or exit polar coordinate interpolation mode (G12.1/G13.1) without G40 (cutter compensation cancel) active, or when an incompatible G-code is commanded during polar coordinate interpolation. The control enforces strict modal group restrictions to prevent calculation errors in the polar transformation.

Causes and Fixes

1
Check program line immediately before G12.1 or G13.1 command. Verify G40 is commanded on the same line or in a previous block after any G41/G42 usage.
2
Review cutter compensation history in program. Access SYSTEM > CURRENT screen and verify G40 is displayed in the modal G-code list (G00 group) before the alarm block.
3
Modify program to explicitly command G40 before G12.1 (polar ON) or G13.1 (polar cancel). Format: N10 G40; N20 G12.1 (or G13.1).
Ensure G40 move completes with sufficient clearance before entering polar mode to avoid tool collision
4
Reset alarm (RESET key), return to program start or safe line, and restart cycle after program correction.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter 1290 changes required
·Persistent alarms after program corrections
·Custom macro interference suspected

Prevention

Always use G40 before G15/G16 commands
Avoid canned cycles in polar interpolation mode
Structure programs with clear modal state transitions
Test polar interpolation sections separately

Common Mistakes

Forgetting G40 before polar commands
Using G41/G42 within polar sections
Mixing canned cycles with polar interpolation
Not understanding modal state inheritance

Related Alarms

144 145 147 010

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