61907

Check the NC program block syntax. Verify CYCLE73/74/75 call includes center point definition: either CC X... Y... Z... (absolute) or G02/G03 with I... J... K... (incremental offsets from start point).

Do not use radius format (R parameter) alone in circular cycles on SINUMERIK 840D; always specify I, J, K or use CC command.

Enable program trace (Diagnostics → Program Trace) and single-step to the failing block. Inspect the interpolator input buffer to confirm center coordinates are present before cycle execution.

Recalculate I, J, K offsets: I and J are incremental distances from start point to center in the XY plane; K is the Z offset. Verify mathematical correctness using the part geometry.

Re-test the corrected NC block with single-cycle execution (MDI mode) before rerunning the full program.

Access the cycle definition file (typically in /prog/cycle/ directory on the control). Locate the formal parameter list for CYCLE73, CYCLE74, or CYCLE75 and identify which parameters define center point.

In the calling NC program, verify all required center point parameters are explicitly assigned with non-zero numeric values before CYCLE call. Example: CYCLE73(X=50, Y=30, Z=0, ...) where X and Y define the center.

Check MD 28040 (CycleFileDir) to confirm the correct cycle path is configured.

If using variable assignment, confirm variables are initialized upstream in the program using assignment statements (e.g., _CC_X=50;) and not left to default (typically 0).

Verify no global reset or variable clear operations between cycle definition and cycle call are erasing center point variables.

Confirm the correct plane is active: insert G17 (XY plane) before CYCLE73/74/75 if the arc lies in XY; use G18 for ZX or G19 for YZ. Verify this matches the part print and toolpath geometry.

Check machine-specific axis naming in Parameters → Machine Data (MD): review MD 30330 (AxisName_1/2/3) to ensure axes are named X, Y, Z and not custom names (e.g., A, B, C) that the cycle does not recognize.

Mismatched axis names between cycle macro and actual hardware will cause center point coordinates to be assigned to wrong physical axes.

In the NC program, explicitly state the plane before the cycle: e.g., 'G17; CYCLE73(...);' at program start or immediately before the failing cycle block.

If custom axis remapping is in use, verify the CYCLE source code uses MD-based axis references or symbolic axis names, not hardcoded numeric indices.