4621

Access Siemens HMI or SINUMERIK Operate menu and navigate to Diagnostics > System Information to confirm control system type (802D vs 840D). Note the current system architecture.

Using Siemens SINUMERIK engineering software (e.g., ShopMill, ShopTurn configuration module) or direct NCK parameter editor, locate machine data parameter $MN_HANDWHEEL_INPUT. Check the numeric value assigned—it should be 1 or 2 for 802D systems only.

Do not modify parameters while CNC is in automatic mode or cycle execution.

If the value is 3 or higher, reduce $MN_HANDWHEEL_INPUT to either 1 or 2. If multiple handwheel functions are required, consider implementing handwheel selector logic via PLC instead of direct NCK mapping.

Save modified machine data and trigger NCK restart via HMI (power cycle or soft reset) to reload $MN_HANDWHEEL_INPUT validation. Verify alarm 4621 no longer appears in Diagnostics > Alarms.

Open the machine data file (typically in NCK directory or via HMI System > Machine Data editor) and locate $MN_HANDWHEEL_INPUT entry. Verify the parameter value is a positive integer (1 or 2 only for 802D).

Check for any leading/trailing spaces, special characters, or decimal points in the parameter value. The correct syntax is: $MN_HANDWHEEL_INPUT = 1 or $MN_HANDWHEEL_INPUT = 2

If syntax errors are found, correct the parameter entry to valid integer format. If uncertain of correct syntax, reference the 802D parameter list documentation (Part no. 6FC5397-xP for your software version).

Perform an NCK cold restart (power off, wait 10 seconds, power on) to force machine data re-parsing. Monitor alarm log to confirm 4621 is cleared.

Review machine commissioning documentation or parameter backup files to determine if this machine was originally configured for 840D. Check part numbers on the control module and compare against Siemens hardware specifications.

If 840D parameters were migrated to 802D, use the Siemens parameter converter tool or manually review all $MN_HANDWHEEL_* and $MN_*_INPUT parameters in the machine data file to ensure 802D compliance (handwheel indices 1–2 only).

Modify $MN_HANDWHEEL_INPUT and any secondary handwheel parameters to values supported by 802D. If more than 2 handwheel inputs are functionally required, consult with machine builder to determine if PLC-based multiplexing or hardware upgrade is feasible.

Save corrected machine data and perform full NCK initialization (clear old parameter cache if needed). Restart control and verify alarm 4621 does not reappear during boot sequence.