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Access Siemens SINUMERIK 840D NCK parameters via HMI: Navigate to Diagnostics > Parameters > Machine Data > select channel and axis. Locate MD 62128 and MD 62129 for the affected axis reported in %2.

Review the current threshold values against the machine's mechanical design specification. Typical safe ranges for rod-guide angle monitoring are ±5-15 degrees; verify with machine builder documentation.

Modification of angle limits requires full machine re-qualification and should not be done without engineering approval.

Increase MD 62128 (lower limit) if minus sign is present, or decrease MD 62129 (upper limit) if plus sign is present, in small increments (0.5-1.0 degree steps) and re-test.

After parameter adjustment, perform a machine zero-point calibration cycle and execute a test contour at reduced feed rate to validate that the alarm no longer occurs.

Immediately stop operation and inspect the affected axis (%2) mechanical components: check rod parallelism to linear guides using a dial indicator at multiple points along the travel range (front, middle, rear).

Continued operation with mechanical misalignment can cause rapid wear and spindle damage.

Measure spindle runout (TIR) at the tool interface if the alarm involves a rotary axis coupled to linear motion. Compare against machine specification (typically <0.005 inch or 0.1mm TIR). Excessive runout indicates bearing wear or spindle imbalance.

Check preload on rod bearing blocks and verify that all mounting bolts connecting the rod assembly to the machine frame are torqued to specification. Loose mechanical connections allow deflection that violates angle thresholds.

If mechanical inspection reveals misalignment >0.5mm, perform realignment/re-squaring of the rod and guides. If alignment is acceptable, contact Siemens field service for servo parameter diagnostics and potential servo gain (MD 36100 series) adjustment.

Access the servo parameter set for the affected axis via HMI: Diagnostics > Parameters > Machine Data > Servo > select axis. Review MD 36010 (proportional gain), MD 36020 (integral gain), and MD 36030 (derivative gain) values.

Compare current servo gains against the commissioning baseline or machine builder's reference values. If gains have been manually increased (often done to compensate for wear), this is a common cause of instability.

Do not modify servo gains on a live production machine without documented commissioning procedure.

Execute a servo tuning test by moving the affected axis at low feed rate (10-20% of rated speed) and monitor the servo error display (Diagnostics > Axis > Actual/Setpoint position deviation). If error oscillates, reduce proportional gain (MD 36010) by 5-10% and re-test.

If oscillation persists, contact Siemens support with servo tuning logs (capture via HMI trace function or oscilloscope data) and complete machine documentation to perform formal gain optimization.