16673

Access Siemens HMI menu: Diagnostics > Alarms > Search 16673 to confirm channel, block number, and leading axis/spindle name listed in the alarm.

Navigate to NCK Parameters menu and locate MD18452 (COUP_MAX_NUMBER_OF_CP). Document the current value—this is the limit that was exceeded.

Review the NC program block referenced in the alarm (Channel %1, Block %2) to count all active COUPLE or COUPLE_AR commands targeting the spindle or axis named in %3.

Use SINUMERIK Editor or the integrated program viewer to inspect the exact coupling commands in context.

Increase MD18452 to a value equal to or greater than the total number of coupling points required. Typical range is 1–4 per spindle. Recompile the program and retry.

Verify with machine OEM that increasing this parameter does not exceed NCK memory constraints or real-time performance budgets.

Inspect the alarm block in the NC program and search for all COUPLE, COUPLE_AR, and UNCOUPLE commands in the surrounding block range (±10 blocks).

Verify that UNCOUPLE commands are executed before new COUPLE commands in the same spindle/axis control sequence. Check MD18452 semantics in Siemens SINUMERIK 840D/840DE/828D documentation for coupling lifecycle rules.

Refactor the NC program to serialize coupling activations: fully decouple the previous master–slave relationship before activating a new coupling point on the same spindle.

Ensure sufficient dwell time (G04 / WAITFOR) between UNCOUPLE and subsequent COUPLE commands to allow NCK state synchronization.

Re-test the program block. Monitor the Diagnostics > Coupling Status screen to confirm active coupling count remains ≤ MD18452.

Verify the spindle assignment in the alarm (%3) and confirm which axis group (primary/AXG1/AXG2) it belongs to via NCK Parameters > Axis Assignment or Siemens Automation Tool.

Check if SPCON (spindle coupling) commands are active in the program and whether they are generating implicit coupling points in addition to explicit COUPLE commands. Review the program for both explicit and implicit master–slave relationships.

Cross-reference MD18452 with MD18450 (COUP_MAX_NUMBER_PER_AXIS_GROUP) and MD18451 (COUP_MAX_NUMBER_OF_AXES). Ensure the spindle's allocation does not conflict with other axes in its group.

Contact machine OEM or Siemens to confirm correct coupling budget allocation if multiple spindles are synchronized in the same axis group.

Adjust MD18452 or redistribute spindle coupling logic across multiple cycles to reduce simultaneous coupling activation count. Retest with Diagnostics > NCK Status to monitor active coupling points in real time.