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FANUC Controller
Program/G-code · Intermediate · 30-60 minutes
Fanuc Alarm 5302 - ILLEGAL COMMAND IN G68 MODE
Fanuc alarm 5302 occurs when the CNC detects a G-code command that is prohibited during coordinate rotation mode (G68). Commands such as tool radius compensation (G41/G42), canned cycles, coordinate system selection (G54-G59), or certain work coordinate changes cannot be executed while G68 is active. This is a program structure error requiring G-code modification.
5302
Fanuc Alarm 5302 - ILLEGAL COMMAND IN G68 MODE
SYSTEM ALARM 5302
Fanuc alarm 5302: SYSTEM ALARM 5302. 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
Fanuc alarm 5302 occurs when the CNC detects a G-code command that is prohibited during coordinate rotation mode (G68). Commands such as tool radius compensation (G41/G42), canned cycles, coordinate system selection (G54-G59), or certain work coordinate changes cannot be executed while G68 is active. This is a program structure error requiring G-code modification.
Causes and Fixes
- 1
Review the program line immediately before alarm occurrence. Press SYSTEM > ALARM to view alarm history with program sequence number and identify the exact G-code block.
- 2
Search the program for G41 or G42 commands that appear after G68 and before G69 (rotation cancel). Verify no compensation offset numbers (D codes) are called in rotation mode.
- 3
Restructure program to cancel G68 with G69 before enabling G41/G42, or activate compensation before entering G68 mode. Ensure G40 (compensation cancel) is active before any G68 call if reordering is not possible.
Changing compensation sequence may affect tool path. Verify with graphics simulation before running.
- 4
Check parameter 5006 bit 3 (OFC) which affects offset behavior during rotation. Setting should typically be 0 for standard operation. Access via SYSTEM > PARAM > [5006] > [BIT].
Call a technician if:
- ·Parameter modifications required beyond standard G-code restrictions
- ·Machine-specific coordinate transformation limitations
Prevention
- Always cancel G68 with G69 before using restricted commands
- Structure programs with coordinate transformations at the beginning
- Use program simulation to verify G68 compatibility before running
Common Mistakes
- Forgetting to cancel G68 before canned cycles
- Attempting to change work coordinates during rotation
- Mixing multiple coordinate transformation functions
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