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Siemens SINUMERIK Controller
Servo/Axis · Intermediate · 30-120 minutes
Siemens 840D 6442 - Channel function not executable. No tool assigned to desired
Alarm 6442 fires when the NCK cannot locate a tool at its assigned magazine position because the PLC tool changer logic has either unloaded the tool, rejected it during a tool change cycle, or failed to confirm tool presence at the storage location. This typically occurs when a preparatory command (G-code) requests tool execution but the PLC status word indicates tool unavailability or the tool change with reject function is active.
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Siemens 840D 6442 - Channel function not executable. No tool assigned to desired
Channel function not executable. No tool assigned to desired
Siemens SINUMERIK alarm 6442: Channel function not executable. No tool assigned to desired. 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
Alarm 6442 fires when the NCK cannot locate a tool at its assigned magazine position because the PLC tool changer logic has either unloaded the tool, rejected it during a tool change cycle, or failed to confirm tool presence at the storage location. This typically occurs when a preparatory command (G-code) requests tool execution but the PLC status word indicates tool unavailability or the tool change with reject function is active.
Safety
- Refer to Siemens documentation
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Navigate to Diagnostics > PLC > Tool Changer Status and verify the current magazine location state. Check PLC data word assignment (typically DW 200-220 range) for tool presence confirmation flags.
- 2
Review the active PLC program logic block for tool change sequences. Verify that the unload command has not been triggered prematurely before the tool selection acknowledgment (PLC status = 7 'Repeat tool selection') is received.
Do NOT modify PLC logic while in AUTO mode; place CNC in JOG or EDIT mode first.
- 3
Check Machine Data MD 20070 (Tool selection confirmation time) and MD 20061 (Tool changer stroke/positioning time) to ensure timing allows PLC to complete tool load before NCK executes the preparatory command.
- 4
Verify tool magazine slot occupancy using Maintenance > Tool Management > Magazine Overview. Manually reload the required tool into the assigned location and confirm PLC acknowledgment before retrying the NC program.
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