6423

Access Siemens SINUMERIK Operate > Diagnosis > Machine Data and navigate to MD 37100 (Magazine: max. number of locations). Record the configured maximum slot number.

Do not modify machine data while spindle is rotating or tool change is in progress.

Cross-reference the alarm parameters: note the requested location %2 from the alarm message and compare against the MD 37100 value. Verify that the tool offset record in the tool table (Operate > Tool Management > Tool Offsets) does not contain an invalid magazine location reference.

If the tool table entry is incorrect, edit the tool record via Operate > Tool Management and set the magazine location to a valid slot within the range 1 to MD 37100. Save and activate the new tool data via Shift+F4 in the Tool Management module.

Execute an M06 tool change command or use the MMC Manual Tool Change dialog to confirm the servo motion succeeds. If alarm persists, verify magazine initialization by running POWER UP in Diagnostics to reset the tool changer homing.

Manual tool change in Operate mode requires spindle stop and appropriate safety interlock verification.

Open Diagnostics > Parameters > Machine Data and verify MD 37000 (Magazine type: 1=ATC drum, 2=linear, 3=matrix) matches the physical magazine on the machine. Cross-check MD 37010 (Magazine assignment to active spindle) confirms the tool changer is assigned to the working spindle channel.

In Tool Management, confirm that all tool records reference the correct magazine ID in the 'Magazine' field. Tools assigned to a non-existent or disabled magazine will trigger 6423. Delete or reassign any orphaned tool entries.

Perform a cold restart (Siemens NC Stop, then Power Cycle NCU) to reload machine data and reinitialize the magazine geometry. This ensures the NCK re-validates all MD parameters before the next tool change.

Power cycle will interrupt any running program; ensure the machine is in a safe state before restart.

After restart, manually jog the magazine to confirm physical functionality (use Operate > Manual > Jog, or PLC direct control via diagnostic panel). Execute a simple M06 to verify the servo motion completes without alarm 6423.

Access Diagnostics > PLC > Monitoring and search for the tool change function block (typically 'TOOL_CHANGE' or 'ATC_MOVE' in the PLC program). Inspect the input parameters, especially the location slot number being passed to the NCK. Compare against the magazine capacity defined in MD 37100.

Do not modify running PLC code without proper authorization; use breakpoints and online diagnostics instead.

Enable detailed logging in Diagnostics > Trace > System Trace and set filter to 'Tool Change Commands' and 'Servo Errors'. Run a manual tool change command and capture the trace output. Review the exact location value %2 sent to the NCK—this will confirm whether the PLC is generating an invalid request.

If the PLC logic is faulty, contact the machine OEM or reprogramming specialist to correct the tool selection algorithm. Alternatively, if the MMC input dialog is the source, verify that dropdown lists in the Tool Change dialog are correctly populated from the tool table and bound to valid magazine slots.