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Siemens SINUMERIK Controller
System · Intermediate · 30-120 minutes
Siemens 840D 20121 - Axis: Configuration error in compensation table
Alarm 20121 indicates invalid compensation table configuration where the axis compensation parameters violate the mandatory constraint: $AN_CEC_MAX must be greater than or equal to $AN_CEC_MIN, and $AN_CEC_STEP cannot equal zero. The NCK automatically disables the affected compensation table and requires parameter correction before re-enabling interpolatory compensation.
20121
Siemens 840D 20121 - Axis: Configuration error in compensation table
Axis: Configuration error in compensation table
Siemens SINUMERIK 840D alarm 20121: Axis: Configuration error in compensation table. 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 20121 indicates invalid compensation table configuration where the axis compensation parameters violate the mandatory constraint: $AN_CEC_MAX must be greater than or equal to $AN_CEC_MIN, and $AN_CEC_STEP cannot equal zero. The NCK automatically disables the affected compensation table and requires parameter correction before re-enabling interpolatory compensation.
Safety
- Refer to Siemens documentation
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Navigate to Diagnostics > Parameters > Machine Data > Axis-specific > Compensation Tables (MD 34700-34799 range) for the affected axis.
- 2
Verify MD 34710 ($AN_CEC_MAX) and MD 34711 ($AN_CEC_MIN) values. Confirm $AN_CEC_MAX >= $AN_CEC_MIN numerically. Swap or correct values if inverted.
Ensure units match the axis measurement system (typically mm or degrees).
- 3
Save corrected parameters using PLC menu Save > Write to ROM or use Shop Mill/Turn parameter transfer function.
- 4
Perform Warm Restart (CTRL+Warm Start) or full NCK power cycle to reload compensation table configuration and clear alarm 20121.
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