The "Waiting for NCK connection" message on a Sinumerik 810D is a common startup error indicating that the Human Machine Interface (HMI) cannot communicate with the Numeric Control Kernel (NCK). This often occurs after a long power-down, a battery failure, or corrupted data. Troubleshooting the "Waiting for NCK Connection" Error 1. Immediate Hardware Check
Before diving into software resets, inspect the CCU (Compact Control Unit) card behind the machine panel:
7-Segment Display: A healthy unit typically shows a "6" with a flashing decimal point once fully booted.
LED Status: Check the lights. If the SF (System Fault), PS (PLC STOP), or PF (PLC Fault) LEDs are lit red, the PLC is likely in a stop state or has corrupted data.
Cabling: Ensure the MPI/Profibus cables and connectors are secure and that any "On/Off" termination switches are correctly set. 2. Power Cycle and Warm Restart
Sometimes a simple power cycle can resolve temporary communication glitches. If that fails, a warm restart via the manufacturer setup menu may re-establish the connection. 3. Addressing Data Loss (Most Common Cause)
If the machine was powered off for an extended period, the internal battery may have failed, leading to the loss of the NC and PLC memory.
Check the Battery: If it’s dead, replace it first to prevent recurring data loss. sinumerik 810d waiting for nck connection
Verify Backups: Ensure you have latest .ARC backup files (NC and PLC archives) before proceeding with a reset. 4. NCK and PLC General Reset Sinumerik 810D - Waiting for response from nck - SiePortal
Based on two decades of field service reports, there are five primary reasons for the 840D/810D waiting for NCK connection fault.
Author: Technical Service Report
System: Siemens SINUMERIK 810D
Error Message: "Waiting for NCK Connection" / "Waiting for connection to NCK"
Look at the main drive/CNC unit (usually the large module on the left of the electrical cabinet).
"Waiting for NCK Connection" is a message that tests the patience of a machinist. It turns a precision tool into a paperweight. However, 90% of the time, the root cause is simple: power fluctuation or a loose cable.
Start with the multimeter before you start ordering expensive boards. In the digital age of manufacturing, sometimes the most complex computer error is solved by simply tightening a screw on a power supply.
The "Waiting for NCK Connection" error on a Sinumerik 810D generally indicates a communication failure between the HMI (Human Machine Interface) and the NCK (Numerical Control Kernel). This is often caused by data loss due to a dead battery, a hardware failure in the CCU (Compact Control Unit), or corrupted software. Common Solutions & Troubleshooting Steps Check the CCU LEDs and 7-Segment Display: Inspect the CCU card behind the back panel. The "Waiting for NCK connection" message on a
A normal, ready state typically shows a "6" on the 7-segment display and two green LEDs lit.
If you see red LEDs like SF (System Fault), PS, or PF, it indicates a hardware or software error.
Battery Replacement: This is a frequent cause if the machine has been powered down for a long time. If the battery dies, the NCK and PLC data stored in SRAM are lost, causing the connection failure. Perform an NCK/PLC Reset and Restore:
Perform a "Clear" or "Reset" of both the NCK and PLC memory.
Set the rotary switch S4 to position "2" (STOP) to facilitate loading.
Reload the machine-specific NC and PLC archives (.ARC files) using a tool like SinuCom PCIN or via the HMI service screen.
Check Cables and Settings: Ensure the MPI cable and connectors are secure. Verify that the HMI settings for the operator panel match the machine's expected NCK address (standard is usually 13). Primary Culprits: Why Does the Error Occur
Hardware Replacement: If memory clears and restores do not work, the CCU board itself may be defective and require replacement. Documentation & Tools Sinumerik 810D - Waiting for response from nck - SiePortal
The message "Waiting for NCK Connection" (or Alarm 120202) on a Sinumerik 810D indicates that the Human-Machine Interface (HMI) cannot communicate with the Numerical Control Kernel (NCK). This is most frequently caused by a loss of internal memory data on the Compact Control Unit (CCU) due to a dead backup battery or an extended period of machine power-down. Common Causes
Data Loss: Battery failure often causes the CCU to lose its NCK and PLC parameters, leaving it unable to boot into a functional state.
Hardware Issues: Loose data cables (MPI/Profibus), poorly seated cards, or a faulty CCU or PCU (Power Control Unit).
Communication Errors: Incorrect node addresses or faulty transmission rates on the bus. Standard Troubleshooting Procedure
Before proceeding, ensure you have a valid NC/PLC archive backup (usually an .ARC file). Sinumerik 810D - Waiting for response from nck - SiePortal
SHIFT + ALARM CANCEL while booting HMI → enter password EVENING → NCK reset.If the battery failed, your machine is "forgetting" who it is.
.ARC or .ARD file). You cannot hand-type these parameters.Machine: DMU 50 with 810D
Symptom: "Waiting for NCK connection" after power failure.
Diagnosis: NCU SF red flashing; PLC stop due to lost program.
Solution: Reload PLC program via memory card, then power cycle → connection restored. Time: 20 minutes.