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In SINUMERIK program, verify CYCLE950 contour definition has no duplicate points or collinear segments. Use G00/G01/G02/G03 blocks with unambiguous XY coordinates. Check that contour is completely closed (last point = first point or implicit closure).

Do not mix incompatible interpolation modes; ensure all contour segments use consistent plane definition (G17/G18/G19).

Review contour path in NCK Diagnostics menu: Monitoring > Block Display. Manually step through CYCLE950 blocks and confirm each segment has measurable length and distinct start/end points.

Redraw contour in CAM software ensuring clockwise or counter-clockwise consistency. Export and re-post CNC code, verifying no zero-length moves (G00 X10 Y10 / G00 X10 Y10) exist in contour definition.

Test simplified contour (rectangle or circle) with CYCLE950 to isolate whether issue is geometry-specific or parameter-related.

Access NC Parameter screen and review CYCLE950 call statement. Verify RO (roughing overlap) is positive and ≤ tool radius. Confirm DP (depth increment) is positive. Check CDIR parameter: 1=clockwise, 2=counter-clockwise. Ensure CDIR matches actual contour direction.

Setting CDIR opposite to actual contour winding will cause direction ambiguity errors.

In Diagnostics > Machine Data menu, navigate to MD20060 (TOFFON behavior). Set to 1 (dynamic TRC) if using tool radius compensation with CYCLE950. Verify MD20062 (TRC ramp type) is configured for your control version (typically 1 or 2).

Check contour plane definition in CYCLE950 call: plane must match active G17/G18/G19 setting. Confirm tool axis assignment in Machine Data MD20090 (tool axis vector) matches cycle expectation.

Simplify CYCLE950 parameters: set SDIS=0 (no safety distance), use minimal RO/DP values, explicitly define CDIR. Re-test to isolate parameter interaction.

Note the alarm block reference %1 (channel) and %2 (block number). Use Diagnostics > Alarms > Message Detail to view full block context. Cross-reference with source CNC program to identify exact CYCLE950 call line.

Block number in alarm refers to NCK internal block counter, not program line number.

Export CNC program and check for floating-point coordinate values with excessive decimal precision (>5 decimals after rounding). Round all XY contour coordinates to machine resolution (typically 0.001mm). Re-post code.

If contour uses splines or complex arcs, verify arc center points (I, J, K) are explicitly defined and within tolerance. For splines, confirm knot vector is monotonically increasing. Use CAM post-processor G-code validation tool.

If issue persists, check Siemens Service Bulletins for 840D firmware version (Diagnostics > System Info > SW version). Update to latest patch level for SINUMERIK 840D/FM. Clear NCK memory and reload program.