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Check Drive Communication Status

Navigate to Diagnostics > Hardware > Drive and verify all configured drives show 'Ready' status. Check for red X marks indicating communication loss.

Use HMI function key 'Drive Status' for quick overview of all axis communication states.

Verify PROFIBUS/PROFINET Configuration

In SINAMICS Startdrive, check bus configuration matches machine data MD30xxx series parameters. Verify baud rate and station addresses.

Never change bus addresses while system is powered - always power down completely first.

Inspect Physical Bus Connections

Check PROFIBUS/PROFINET cables for damage, verify terminating resistors at bus ends, and ensure proper shield grounding at cabinet entry points.

Use SIMATIC NET tools to perform bus diagnostics and measure signal quality.

Compare Drive Parameters

Access Service > Machine data and compare current MD32xxx servo parameters against backup or commissioning documentation.

Use 'Parameter comparison' function in SINAMICS Startdrive to identify parameter deviations.

Restore Default Servo Settings

Navigate to Commissioning > Axis > Basic settings and perform 'Restore factory defaults' for affected axis, then reconfigure essential parameters.

Document current settings before restoration - this will reset all axis-specific tuning parameters.

Perform Drive Optimization

Run automatic servo optimization via Commissioning > Axis > Optimization to recalculate control parameters and verify mechanical coupling.

Ensure machine is mechanically decoupled during optimization to prevent damage from unexpected movements.

Check NCU LED Status

Examine NCU front panel LEDs - SF (System Fault) and BF (Bus Fault) indicators. Red SF LED confirms internal hardware issues.

LED patterns follow standard SIMATIC diagnostic codes - consult NCU manual for specific blink sequences.

Verify X122/X132 Connections

Power down system and inspect servo interface connector pins for corrosion, bent pins, or loose connections. Check cable continuity.

Always use proper ESD protection when handling NCU connectors - static discharge can damage interface circuits.

Test with Minimal Configuration

Disconnect all but one servo axis and attempt system startup to isolate hardware vs. configuration issues.

Use SINAMICS commissioning software to test individual drive communication bypassing NCU if possible.

Monitor Supply Voltages

Use multimeter to verify 24VDC supply stability (±5%) and check servo drive DC bus voltage via Diagnostics > Drive > Supply voltages.

Check voltage under load conditions - many supply issues only appear during axis movement.

Inspect Power Supply Connections

Verify all power supply terminals are tight, check for overheated connections, and measure voltage drop across supply cables.

Use lockout/tagout procedures - servo drives contain high voltage even when control power is off.

Check Regenerative Resistor Circuit

Verify brake resistor connections and resistance values match drive specifications. Check for overheating or damage.

Monitor DC bus voltage during rapid deceleration - excessive voltage indicates brake resistor problems.

Check Encoder Signal Quality

Navigate to Diagnostics > Drive > Encoder and monitor signal amplitude, frequency, and error counters for all feedback systems.

Use oscilloscope on encoder signals if available - look for noise, signal dropouts, or amplitude variations.

Verify Encoder Cable Routing

Inspect encoder cables for proper shielding, separation from power cables, and secure connections at motor and drive ends.

Never route encoder cables in same conduit as motor power cables - EMI will corrupt position feedback.

Test Encoder Functionality

Use Service > Encoder test function to verify position feedback accuracy and detect intermittent encoder faults.

Compare actual vs. commanded positions during slow manual movements to identify feedback errors.