16748

Retrieve the active gear stage speed limits from Siemens HMI: Diagnostics > Spindle > Gear Stage Parameters. Note the Min/Max RPM values (typically stored in MD20140 for stage 1, MD20141 for stage 2).

Do not assume speed ranges from machine nameplate; verify parameterized values in the control.

Review the NC program block triggering alarm 16748 (shown in block %2). Confirm the S-value and compare against the gear stage range identified in step 1.

Modify the NC program: insert a separate G331 block *before* the speed change to pre-select the correct gear stage, then command the S-value in the following block. Example: G331 (gear 2) / G0 / S1500 M3 (speed within stage 2 range).

Ensure MD20070 (base frequency) matches the spindle motor nameplate to avoid cascading speed calculation errors.

Verify tapping cycle parameters in SD43310/SD43320 (tapping spindle offset/dwell). Re-test the program and monitor actual spindle speed via Diagnostics > Spindle > Actual Speed.

Access machine data via HMI > Parameterization > Spindle. Pull MD20050 (spindle max speed), MD20070 (base frequency), MD20140, and MD20141 into a diagnostic log.

Requires service-level access (Siemens service login); standard operator cannot modify these without proper authorization.

Cross-reference the retrieved MD values against the spindle motor nameplate and gearbox reduction ratio (typically 1:1 for stage 1, 1:2 for stage 2 on common tapping heads). Validate that MD20140 and MD20141 reflect actual capability.

If ranges are incorrect, correct MD20140/MD20141 using Parameterization menu. Ensure lower speed stage has lower max RPM than higher stage (e.g., Stage 1: 0–1200 RPM, Stage 2: 1200–3000 RPM).

Apply changes offline; perform spindle zero-speed verification (G04 P1 M5) before resuming tapping cycles.

Review the NC program sequence leading to G331. Ensure M19 (spindle orientation) or G04 (dwell) is executed *before* G331 to allow spindle speed to stabilize.

Tapping on SINUMERIK typically requires G331 + M3/M4 + wait-for-spindle M25 in the same block or immediately following.

Check SD43300 (tapping mode) and SD43310 (spindle speed offset) settings. Confirm tapping mode is enabled (SD43300 = 1) and offset is within ±20% of programmed speed per Siemens manual.

Verify spindle feedback encoder (MD20062 encoder pulses per spindle turn) is correctly parameterized. Run test cycle at reduced feedrate (20%) and monitor Diagnostics > Spindle > Sync Error; acceptable range is typically ≤2% slip.