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Calculate Arc Geometry

Measure the distance from start point to center (I/J/K) and end point to center - these radii must be identical within the control's tolerance (typically 0.0002").

Use CAM software's arc verification tools or manual trigonometric calculations to validate geometry before posting code.

Check Parameter 33 Arc Tolerance

Access SETTING > PARAMETERS > enter 33 > verify arc tolerance setting (default 0.0002). Increase slightly if dealing with imported geometry from CAD systems.

Increasing arc tolerance beyond 0.001" may affect part accuracy and surface finish.

Reprogram Arc Command

Edit the G02/G03 line with corrected I/J/K values or convert to R-format (G02 X__ Y__ R__) to let the control calculate the center point automatically.

Verify with Graphics

Use GRAPHICS mode to visually verify the arc path before running the program - invalid arcs will show as straight lines or erratic paths.

Calculate Minimum Radius

Measure the straight-line distance between arc start and end points - the R value must be at least half this distance for a valid arc solution.

For 180-degree arcs, R equals exactly half the chord length; for smaller arcs, R must be proportionally larger.

Check for Ambiguous Arc Solutions

When R value allows both major and minor arc solutions, specify the intended path: use positive R for minor arc (<180°) or negative R for major arc (>180°).

Ambiguous R values can cause the control to select the wrong arc direction, potentially causing crashes.

Convert to I/J/K Format

If R-format continues to cause issues, convert to I/J/K incremental center point format for explicit arc definition and better control reliability.

Check Active Scaling

Press CURRENT COMMANDS to verify if G51 scaling is active - scaling factors applied to arc centers can create invalid geometry ratios.

Arc centers (I/J/K) are scaled differently than endpoints, often causing radius mismatches in scaled programs.

Verify Work Coordinate Systems

Check WORK OFFSETS display for active G54-G59 values - large offset values combined with arc commands can exceed the control's calculation range.

Work offsets beyond ±99999.9999 can cause computational overflow in arc calculations.

Cancel Scaling and Test

Program G50 to cancel scaling, then test the arc command - if successful, the issue is scale-related and requires arc parameter adjustment.

Adjust Arc Programming

Reprogram arcs with scaling considerations or move arc commands outside of scaled program sections to avoid geometric conflicts.

Verify Active Plane

Check CURRENT COMMANDS display for active plane: G17 (XY), G18 (XZ), or G19 (YZ) - ensure it matches the intended arc plane.

G17 uses I/J, G18 uses I/K, G19 uses J/K - using wrong parameters for the active plane triggers this alarm.

Match Parameters to Plane

Correct the arc parameters: G17 plane uses I (X-axis) and J (Y-axis), G18 uses I (X-axis) and K (Z-axis), G19 uses J (Y-axis) and K (Z-axis).

Program Explicit Plane Selection

Add the correct G17, G18, or G19 command before the arc move to ensure proper plane selection and parameter interpretation.