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FANUC Controller
Program/G-code · Intermediate · 15-30 minutes
Fanuc Alarm 163 - ILLEGAL COMMAND IN G68/G69
Alarm 163 occurs on T-series (lathe) systems during balance cut or two-path control when G68 (coordinate system rotation) or G69 (coordinate system rotation cancel) is commanded in only one path instead of both paths simultaneously. Both the main and sub spindle paths must execute G68/G69 together during balanced cutting operations to maintain synchronization.
Fanuc Alarm 163 - ILLEGAL COMMAND IN G68/G69
SYSTEM ALARM 163
Fanuc alarm 163: SYSTEM ALARM 163. 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 163 occurs on T-series (lathe) systems during balance cut or two-path control when G68 (coordinate system rotation) or G69 (coordinate system rotation cancel) is commanded in only one path instead of both paths simultaneously. Both the main and sub spindle paths must execute G68/G69 together during balanced cutting operations to maintain synchronization.
Causes and Fixes
Review the NC program at the alarm occurrence block. Check if G68 or G69 appears in only Path 1 or Path 2 program sections without the corresponding command in the other path.
Verify balance cut mode status by checking parameter 14701 (balance cut enable) and reviewing the program for M-codes that activate two-path control (typically M300-M399 range, machine-specific).
Modify the program to command G68 or G69 in both paths at the same sequence number using synchronized block format (e.g., N100 in both Path 1 and Path 2), or use wait codes (M200/M201 or similar) to ensure simultaneous execution.
Ensure both paths use identical G68 rotation center coordinates and rotation angles to prevent collision between synchronized tools.
If coordinate rotation is not required during balance cut, remove G68/G69 from the balance cut section and reposition before or after the two-path control is deactivated.
Call a technician if:
Prevention
Common Mistakes
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