3000

Check Physical Override Controls

Inspect the machine control panel feed override rotary switch or potentiometer. Verify it's not in the 0% position and rotate through its range to check for mechanical binding.

On older SINUMERIK systems, the override pot can develop dead spots - rotate slowly and feel for mechanical resistance.

Verify HMI Override Display

Access HMI screen 'Machine' → 'Override' and check the feed override percentage display. Use the HMI controls to increase override above 0%.

Ensure machine is in a safe state before increasing feed override as motion will resume immediately.

Test Override Response

Gradually increase feed override to 10-20% and verify the alarm clears. Test override functionality through full range (0-120%) to confirm proper operation.

Access NCK Diagnostics

Navigate to HMI 'Diagnostics' → 'NCK' → 'Analog Inputs' and check the feed override input voltage reading. Normal range should be 0-10V corresponding to 0-120% override.

Document the voltage reading at different potentiometer positions to identify dead zones or erratic behavior.

Inspect Override Potentiometer Wiring

Check electrical cabinet connections to the override potentiometer, typically connected to NCK analog input module. Verify +24V supply, 0V reference, and analog signal wiring integrity.

Power down the system before checking electrical connections to prevent damage to analog input modules.

Measure Potentiometer Resistance

Disconnect potentiometer and measure resistance across terminals while rotating. Should show smooth resistance change from 0-10kΩ (typical). Replace if open circuit or erratic readings detected.

Check PLC Override Interface

Access HMI 'Diagnostics' → 'PLC' → 'Interface Signals' and examine DB31.DBD0 (feed override from PLC). Verify PLC is not writing 0% override value to NCK.

Cross-reference with machine manufacturer's PLC documentation for specific DB assignments as these can vary by machine builder.

Review Safety Interlock Status

Check machine safety system status through HMI 'Machine' → 'Safety' menu. Verify all safety doors, light curtains, and emergency stops are properly reset and not forcing override to zero.

Never bypass safety interlocks - resolve the underlying safety condition causing the override restriction.

Examine NCK Override Parameters

Access 'Commissioning' → 'Machine Data' and check MD11210 (override limits) and MD11200 (override default values). Verify these parameters allow override above 0%.

Identify Override Input Module

Locate the NCK analog input module in the electrical cabinet, typically labeled as 'Analog In' or 'AI'. Check module LED status indicators for fault conditions (red LEDs).

Consult the machine electrical drawings to identify which specific analog input channel is used for feed override - commonly AI0 or AI1.

Verify Input Signal at Module

Measure voltage at the analog input module terminals while adjusting override potentiometer. Should read 0-10V DC. If voltage is present but NCK shows 0%, suspect module failure.

Use appropriate DMM settings and ensure proper grounding when measuring analog signals to prevent module damage.

Test Module Substitution

If available, swap the analog input module with a known good spare or temporarily reassign override to a different analog input channel through machine data MD configuration.

Check Override Lock Status

Access HMI 'Machine' → 'Override' screen and look for override lock indicators or disabled controls. Check if override adjustment is grayed out or locked.

Some SINUMERIK versions have password-protected override limits - check if higher access level is required to modify override values.

Verify Operating Mode

Confirm the NCK operating mode through HMI status display. Certain modes like 'Setup' or special maintenance modes may restrict override functionality.

Changing operating modes may affect other machine functions - coordinate with production before mode changes.

Reset HMI Override Function

Perform HMI restart through 'System' → 'Restart HMI' to clear any software locks. If problem persists, check machine data MD11xxx series for override restrictions.