What causes FANUC alarm 328?

G41 or G42 tool nose radius compensation is specified on the wrong side of the part profile relative to the cutting direction in a G71 or G72 cycle. The finish profile defined in the G71 or G72 cycle moves in a direction that conflicts with the active G41/G42 compensation command. G71 used for outer diameter turning but G42 specified instead of G41, or vice versa, causing the blank side to be on the wrong side. G72 face turning cycle has the compensation direction swapped relative to the actual tool approach and profile direction. The start point of the profile sequence is positioned incorrectly, causing the control to detect an invalid blank side relationship with the compensation direction.

How do I fix FANUC alarm 328?

1. Identify whether you are running a G71 OD/ID roughing cycle or G72 face roughing cycle, then check which G41 or G42 command is active in the finish profile block sequence. 2. For G71 OD turning, the tool typically cuts from right to left and the compensation should be G42. For G71 ID boring, it is usually G41. Verify your setup matches this logic. 3. For G72 face turning, the tool cuts in the Z axis direction. Check that G41 or G42 matches the actual side of the material being removed relative to the tool path direction. 4. Review the starting point coordinates of the profile definition blocks called by the G71 or G72 cycle. The profile start point must be positioned so the blank side is clearly on the correct side of the tool path. 5. Temporarily remove G41 or G42 from the finish profile and run a dry cycle to verify the profile shape is correct, then re-add the correct compensation command based on the confirmed cutting direction. 6. Check the Fanuc parameter settings for the G71 or G72 cycle type if using Format B programming, as different parameter settings affect how the control interprets the blank side and compensation direction.

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FANUC Controller

Program/G-code · Intermediate · 20-45 minutes

Alarm 328

Fanuc Alarm 328 - ILLEGAL WORK POSITION IN TOOL NOSE RADIUS COMPENSATION

Fanuc Alarm 328 occurs when the tool nose radius compensation direction (G41/G42) is incorrectly specified relative to the workpiece geometry in roughing cycles G71 or G72. The CNC detects that the compensation side would cause the tool to cut into the finished part profile rather than away from it during the multiple repetitive cycle. This is a program logic error where the cutter compensation direction conflicts with the cutting pattern direction.

FANUCProgram/G-codeIntermediate20-45 minutes

328

Fanuc Alarm 328 - ILLEGAL WORK POSITION IN TOOL NOSE RADIUS COMPENSATION

FANUC ALARM 328

Root Cause Summary

Fanuc Alarm 328 occurs when the tool nose radius compensation direction (G41/G42) is incorrectly specified relative to the workpiece geometry in roughing cycles G71 or G72. The CNC detects that the compensation side would cause the tool to cut into the finished part profile rather than away from it during the multiple repetitive cycle. This is a program logic error where the cutter compensation direction conflicts with the cutting pattern direction.

Causes and Fixes

1
Review the G71 or G72 block and identify whether G41 or G42 is active. For external turning with G71, verify tool approach direction and finished profile geometry to determine correct compensation side.
2
Check the finish profile geometry (P and Q address blocks in G71/G72). Trace the programmed path direction and verify the tool nose radius compensation keeps the tool on the material removal side, not between stock and finish contour.
3
Swap G41 to G42 or vice versa in the cycle call block, or cancel compensation with G40 before the cycle if tool nose radius compensation is not required for roughing operations.
4
Re-execute the program in single block mode (SINGLE BLOCK key ON) to verify the alarm clears and tool path is correct. Monitor CURRENT COMMANDS screen (POS > PROGRAM) to confirm G41/G42 status.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter changes required beyond standard tool compensation
·Persistent alarm after correcting obvious programming errors
·Custom macro interference suspected

Prevention

Always establish tool nose compensation before entering canned cycles
Use consistent compensation direction throughout roughing operations
Verify tool nose radius and direction parameters match physical tools
Test new programs in single block mode to catch compensation errors early

Common Mistakes

Using G41 instead of G42 for external turning with G71
Leaving compensation active from previous operations
Setting incorrect tool nose direction parameter
Programming compensation changes within P-Q sequences

Related Alarms

327 329 330 331

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