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Siemens SINUMERIK Controller
Tool Changer · Intermediate · 30-120 minutes
Siemens 840D 6401 - Channel tool change not possible: Empty location for tool on
SINUMERIK 6401 fires when the NCK cannot allocate a free tool magazine location for the requested tool during an automatic tool change. This occurs because all suitable locations are occupied, disabled, reserved, or physically incompatible with the tool geometry being loaded.
6401
Siemens 840D 6401 - Channel tool change not possible: Empty location for tool on
Channel tool change not possible: Empty location for tool on
Siemens SINUMERIK alarm 6401: Channel tool change not possible: Empty location for tool on. This alarm indicates a fault or error condition on the SINUMERIK 840D control. Refer to the Siemens SINUMERIK alarm documentation for the complete description and remedy.
Root Cause Summary
SINUMERIK 6401 fires when the NCK cannot allocate a free tool magazine location for the requested tool during an automatic tool change. This occurs because all suitable locations are occupied, disabled, reserved, or physically incompatible with the tool geometry being loaded.
Safety
- Refer to Siemens documentation
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Access Diagnostics > Tool Management > Tool Magazine Status in SINUMERIK HMI. Verify location occupation map matches physical magazine state. Check each location's status bits: free/occupied, enabled/disabled, reserved/available.
Do not manually manipulate tool magazine while diagnostics are running.
- 2
Review MD 20070 (tool magazine max locations) and MD 20071 (location enable/disable mask). Verify disabled locations are intentional. If locations are incorrectly disabled, edit via Parameterization > Tool Management > Magazine Configuration and reload via LOAD TOOL MAGAZINE CONFIGURATION.
Changing MD 20070/20071 requires NCK reset (warm restart). Backup existing configuration first.
- 3
In PLC program (OB_TOOLCHANGE or equivalent), verify tool reservation logic in SD 51100-51199 (tool status data) is not indefinitely holding location reservations. Check for orphaned reservations from interrupted tool changes. Clear stale reservations via PLC interface or manual magazine edit.
- 4
Verify tool preset data (T-numbers mapped to magazine locations) in Machine Data > Tool Data or via TOOL.DEF file. Remove duplicate tool assignments that may reference same location. Use Tools > Check Tool Data Consistency utility.
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