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Siemens SINUMERIK Controller
Overtravel/Limit · Intermediate · 30-120 minutes
Siemens 26008 - Axis QEC: invalid fine step size
Alarm 26008 is triggered when the Quadrant Error Compensation (QEC) fine step size parameter is configured outside the valid range of 1 to 16. This parameter ($AA_QEC_FINE_STEPS) directly impacts NCK computation cycle time and must remain within specification to prevent system instability and timing violations in the control loop.
26008
Siemens 26008 - Axis QEC: invalid fine step size
Axis QEC: invalid fine step size
The fine step size for quadrant error compensation $AA_QEC_FINE_STEPS must be in the range 1 <= fine step size <= 16 because this value has an influence on the computation time of the QEC Control reaction: Alarm display.
Root Cause Summary
Alarm 26008 is triggered when the Quadrant Error Compensation (QEC) fine step size parameter is configured outside the valid range of 1 to 16. This parameter ($AA_QEC_FINE_STEPS) directly impacts NCK computation cycle time and must remain within specification to prevent system instability and timing violations in the control loop.
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
Access Siemens HMI menu: Maintenance > Parameters > Machine Data. Navigate to axis-specific QEC parameters (typically MD34000 series for Axis 1, MD35000 series for Axis 2, etc.).
- 2
Locate $AA_QEC_FINE_STEPS parameter (verify exact MD number in your system documentation, commonly MD34180 or equivalent). Verify current value is between 1 and 16 inclusive.
Do not modify without documenting original value.
- 3
If value is out of range, set to a safe intermediate value (recommend 8 for balanced performance) and confirm with Enter. Trigger MD parameter reload cycle or restart CNC.
Changes to QEC parameters require axis homing and warm restart verification.
- 4
Execute a reference move (G74 or control panel jog) on the affected axis to re-initialize QEC compensation tables and clear alarm 26008.
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