16600

Verify spindle is configured for speed control by checking MD 31500 (spindle type) and MD 31501 (spindle characteristic curve). Confirm spindle encoder feedback is enabled and MD 31502 (actual value feedback type) is set to encoder input.

If spindle type is set to stepper or open-loop mode, M40 automatic gear change will fail.

Check if an M5, M3 without speed ramp completion, or M4 command precedes the programmed speed that triggers alarm 16600. The spindle must reach steady-state speed control before M40 can execute.

Verify PLC interface signals for spindle gear stage request (typically SPA_GEAR_STAGE or equivalent via NCK-PLC handshake) are not blocked by safety interlocks or PLC program logic. Monitor diagnostic data via SIEMENS HMI Diagnostics > Spindle > Gear Stage Information.

Review the NC block %2 that triggered the alarm and extract the programmed spindle speed (S value). Cross-reference with MD 31521 (gear stage 1 max speed), MD 31522 (gear stage 2 max speed), etc., to confirm speed is achievable.

Check MD 31520 (number of gear stages) to ensure all required gear stages are configured. Verify no speed range gaps exist between consecutive gear stages where the programmed speed could fall between max of stage N and min of stage N+1.

If speed ranges overlap correctly and speed is still out of range, the machine spindle hardware cannot achieve the requested speed.

Inspect the machine parameter table in Siemens HMI under Diagnostics > Machine Data > Spindle to visualize all configured gear stage speed ranges graphically. Adjust MD 31521-31525 or reprogram the NC block with an achievable speed value.

Access the spindle control PLC program logic via STEP 7 or Siemens diagnostic interface. Search for the gear stage change request handler (typically labeled M_GEAR_CHANGE or GEARCHANGE_REQUEST block) and identify all conditional statements that gate the change.

Modifying PLC interlocks without authorization may violate machine safety certification.

Check machine status flags: verify operating mode is AUTO (not MANUAL), spindle load is below MD 31530, spindle speed is stable and within transition window (typically below 80% of current stage max), and all safety signals (e-stop, door, coolant) are normal.

Monitor NCK diagnostic counters via Siemens HMI Diagnostics > Spindle > Gear Change Attempts to see if PLC is rejecting requests. If counter increments but gear stage does not change, PLC interlock is active. Contact machine builder to confirm interlock requirements and disable if safe to do so.