4631

Access Diagnostics > Parameters > Machine Data via the HMI operator panel. Navigate to $MN_HANDWHEEL_INPUT and document the current slot value being requested.

Cross-reference the assigned slot number against the PROFIBUS network configuration in SINUMERIK Automation Tool (formerly NCK Tool). Check the PROFIBUS master configuration to verify how many handwheel nodes are actually configured (typically visible under Communication > PROFIBUS > Devices).

Do not assume slot numbers are sequential; verify actual configured device addresses.

If the slot number exceeds available resources, modify $MN_HANDWHEEL_INPUT to reference a valid slot number (e.g., change from slot 5 to slot 1-4). If multiple handwheels are required, ensure corresponding PROFIBUS handwheel modules are physically connected and configured in the control architecture.

Perform a complete control Power Off/Power On cycle (not a soft reset) to reload machine data and reinitialize PROFIBUS communication. Monitor the startup sequence via HMI Diagnostics > System Messages to confirm alarm 4631 no longer appears.

In SINUMERIK Automation Tool, open the PROFIBUS configuration file and navigate to the device list (typically PROFIBUS > Stations or Devices). Verify that handwheel nodes corresponding to the slot index in $MN_HANDWHEEL_INPUT are listed with valid device addresses (e.g., address 6 for handwheel slot 1).

Device addresses must match the slot index mapping defined in the control's PROFIBUS topology.

Physically inspect the PROFIBUS network cabling and handwheel modules. Confirm that the handwheel device assigned to the requested slot is connected to the PROFIBUS trunk, properly terminated, and powered on. Check LED indicators on the handwheel module for communication status (typically green indicates online).

If the handwheel module is missing, either add the hardware to the system and configure its PROFIBUS address in Automation Tool, or modify $MN_HANDWHEEL_INPUT to reference an existing configured slot. Regenerate and download the PROFIBUS configuration to the control.

Perform a PROFIBUS reinitialisation via HMI: Settings > System > PROFIBUS > Reinitialize (or equivalent menu path for your control version). This forces the NCK to rebuild the PROFIBUS device table and revalidate all handwheel slot assignments.

In HMI Diagnostics > Parameters > Machine Data, select $MN_HANDWHEEL_INPUT and verify the parameter value is a positive integer within the valid range (typically 0-3 for slots 1-4, or 1-4 depending on indexing convention). Document the data type displayed (should be 'INT' or 'DINT').

Invalid characters or non-numeric values will cause parsing errors during parameter load.

Check the SINUMERIK 840D firmware version: HMI > Diagnostics > System Information > Software Version. Cross-reference this version against Siemens documentation to confirm PROFIBUS handwheel support is available and that the maximum slot count matches your configuration.