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FANUC Controller
Program/G-code · Intermediate · 5-30 minutes
Fanuc 377 - Illegal command in scaling
Alarm 377 occurs when the control detects an incompatible G-code command while scaling (G50/G51) is active in the part program. Certain commands like canned cycles, reference point returns, and some coordinate system commands cannot be executed when scaling mode is enabled. This is a programming error that requires modification of the NC program sequence.
377
Fanuc 377 - Illegal command in scaling
ILLEGAL COMMAND IN SCALING
Fanuc PS program alarm 377: ILLEGAL COMMAND IN SCALING. This alarm is triggered by an illegal or incorrectly formatted command in the part program, or a programming condition that the Fanuc control cannot execute.
Root Cause Summary
Alarm 377 occurs when the control detects an incompatible G-code command while scaling (G50/G51) is active in the part program. Certain commands like canned cycles, reference point returns, and some coordinate system commands cannot be executed when scaling mode is enabled. This is a programming error that requires modification of the NC program sequence.
Safety
- Verify corrected program or parameters before resuming machining
Causes and Fixes
- 1
Search the program for G51 (scaling ON) commands and identify all active scaling blocks.
- 2
Locate any canned cycle commands (G73, G74, G76, G80-G89) that occur between G51 and G50 (scaling OFF).
- 3
Insert G50 (cancel scaling) before the canned cycle block, then reactivate G51 after the canned cycle completes if scaling is still needed.
- 4
Verify program syntax and test run in single block mode to confirm alarm is cleared.
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