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Siemens SINUMERIK Controller
Spindle · Intermediate · 30-120 minutes
Siemens 840D 20201 - Channel spindle no tool assigned
Alarm 20201 fires when a fine tool compensation (FTC) command is executed on a spindle that has no active tool assignment in the Tool Management System. The NCK cannot apply tool-specific compensation data without a valid spindle/tool relationship established through M6 tool change or equivalent assignment mechanism.
20201
Siemens 840D 20201 - Channel spindle no tool assigned
Channel spindle no tool assigned
Siemens SINUMERIK 840D alarm 20201: Channel spindle no tool assigned. This alarm indicates a program or channel-level error on the SINUMERIK control. The part program or machine function cannot be executed as commanded.
Root Cause Summary
Alarm 20201 fires when a fine tool compensation (FTC) command is executed on a spindle that has no active tool assignment in the Tool Management System. The NCK cannot apply tool-specific compensation data without a valid spindle/tool relationship established through M6 tool change or equivalent assignment mechanism.
Safety
- Refer to Siemens documentation
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Verify M6 or equivalent tool change command precedes any fine tool compensation calls in the NC program. Check program sequence in MDI or manual mode.
- 2
In HMI > Diagnostics > Channel > [Channel#] > Tool Management, confirm tool assignment status shows an active tool number (not 'T0' or empty). If empty, manually execute M6 T[number] M3 S[rpm].
- 3
Verify Tool Table data exists: Menu > Parameters > Machine > Tool Data (MD 32200-32299 range) contains entries matching the tool numbers called in M6 commands.
- 4
If using automated tool changers, check PLC program block FB 'Tool Change' activation and confirm M6 completion handshake signal returns to NCK before FTC execution.
Incomplete M6 cycle handshake will leave spindle/tool assignment incomplete
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