020

Review the G02 or G03 block shown in the alarm display on the CNC screen. Note the current position coordinates and the commanded endpoint coordinates (X, Y, Z values).

Check parameter 3410 (arc radius tolerance) via SYSTEM > PARAM > search for parameter number 3410. Verify the tolerance value - typical values are 500 (0.5mm metric) or 20 (0.020 inch). Lower values make the system more sensitive to radius errors.

Calculate the actual radius discrepancy: measure distance from start point to arc center using IJK values, then measure distance from arc center to endpoint. If difference exceeds parameter 3410 setting, the alarm is correct.

Correct the program by recalculating IJK values or R-word specification, or adjust endpoint coordinates. If the error is within acceptable manufacturing tolerance, temporarily increase parameter 3410 value after management approval.

Increasing parameter 3410 reduces geometric accuracy checking. Document any parameter changes and verify part quality after modification.

Identify whether the arc uses IJK format (incremental center point) or R format (radius value). Press RESET to clear alarm, then use EDIT or MEM mode to view the exact G02/G03 command block causing the alarm.

For IJK format: verify I, J, K values represent the incremental distance from arc START point to arc center, not absolute coordinates. For R format: verify R value is positive for arcs ≤180° and negative for arcs >180°.

Use graphic simulation if available (depending on CNC model: press MENU OFFSET > GRAPHIC or use ladder diagram GP.DISP function) to visualize the programmed toolpath and identify the geometric impossibility.

Correct the program using proper arc calculation formulas or regenerate the program from CAM system with verified post-processor. Re-verify using dry run with single block mode.

Always perform dry run with Z-axis raised or in simulation mode before running corrected arc commands to prevent collision.

Check if G68 (coordinate rotation), G51 (scaling), or cutter compensation (G41/G42) is active before the arc command. Navigate to POSITION > screen and verify WORK coordinate display matches expected values.

Review parameter 3450 (bit 0 - IJK incremental from start point of arc) to verify system is interpreting IJK values correctly. Check parameter 1004 for decimal point input setting consistency with program format.

Insert a G90 absolute positioning command or re-establish work coordinates with G54-G59 before the problematic arc block to eliminate accumulated incremental errors.

If using coordinate transformation, cancel transformations (G50, G69, G40) before the arc block, or increase parameter 3410 slightly to accommodate transformation-related rounding errors while maintaining acceptable geometric accuracy.

Verify that canceling coordinate transformations does not affect other portions of the program. Review entire program logic before implementation.