axismd.ai
Siemens SINUMERIK Controller
System · Intermediate · 30-120 minutes
Siemens 4020 - Identifier used several times in machine data
Alarm 4020 occurs when the NCK machine data configuration contains duplicate identifiers in arrays that define machine axes, Euler angles, direction vectors, interpolation parameters, or intermediate point coordinates. This violates the uniqueness constraint required by the SINUMERIK control system during machine data compilation and initialization.
4020
Siemens 4020 - Identifier used several times in machine data
Identifier used several times in machine data
When determining a name in the NCK tables (arrays) for: machine axes, Euler angles, direction vectors, normal vectors, interpolation parameters and intermediate point coordinates, an identifier has been used that already exists in the control Control reaction: NC not ready. Mode group not ready, also effective for single axes. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm.
Root Cause Summary
Alarm 4020 occurs when the NCK machine data configuration contains duplicate identifiers in arrays that define machine axes, Euler angles, direction vectors, interpolation parameters, or intermediate point coordinates. This violates the uniqueness constraint required by the SINUMERIK control system during machine data compilation and initialization.
Safety
- Only qualified personnel should diagnose and clear control alarms; follow the machine builder's safety procedures and lockout/tagout where hardware work is required.
Causes and Fixes
- 1
Navigate to Siemens HMI menu: Maintenance > Machine Data > Axis Data. Review all axis name entries (typically MD10001, MD10101, MD10201, etc. for axes X, Y, Z respectively).
Do not confuse axis numbers with axis identifiers; verify actual name strings in the MD parameters.
- 2
Check SINUMERIK source files (*.src) or compiled machine data files for duplicate axis identifier assignments. Use text search for identifier strings appearing in multiple MD10xxx entries.
- 3
Rename one of the duplicate identifiers to a unique value (e.g., change 'X_AXIS' to 'X_AXIS_PRIMARY' if duplication exists), then recompile machine data using SINUMERIK parameter editing tool.
Ensure renamed identifier matches any corresponding PLC symbol declarations in the OB data block to avoid secondary conflicts.
- 4
Power-cycle the 840D control to reload machine data tables and verify alarm 4020 clears upon startup.
Seeing Multiple Alarms?
Seeing another alarm with this one? Enter the code.
Get machine-aware diagnosis
AxisMD logs alarms against your actual machines, tracks patterns, and gives AI context your manual doesn't have.
Start freeWas this guide helpful?
Always verify with your machine manual or a certified technician before performing service procedures.