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Siemens SINUMERIK Controller
Overtravel/Limit · Intermediate · 30-120 minutes
Siemens 26009 - Axis QEC: memory overflow
Alarm 26009 fires when the QuickErrorCompensation (QEC) memory buffer overflows due to excessive characteristic curve points exceeding MD $MA_MM_QEC_MAX_POINTS. This occurs when the product of coarse and fine interpolation steps, optionally doubled for direction-dependent characteristics, exceeds the NCK allocated memory for QEC lookup tables.
26009
Siemens 26009 - Axis QEC: memory overflow
Axis QEC: memory overflow
The product of the data $AA_QEC_COARSE_STEPS+1 and $AA_QEC_FINE_STEPS must not exceed the maximum number of the characteristic curve points (MD38010 $MA_MM_QEC_MAX_POINTS). With a direction- dependent characteristic, this criterion applies to 2 * ($AA_QEC_COARSE_STEPS+1) * $AA_QEC_FINE_STEPS! Control reaction: Alarm display.
Root Cause Summary
Alarm 26009 fires when the QuickErrorCompensation (QEC) memory buffer overflows due to excessive characteristic curve points exceeding MD $MA_MM_QEC_MAX_POINTS. This occurs when the product of coarse and fine interpolation steps, optionally doubled for direction-dependent characteristics, exceeds the NCK allocated memory for QEC lookup tables.
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
Navigate to Diagnostics > Parameters > Machine Data (MD) on the SINUMERIK 840D HMI. Query MD $MA_MM_QEC_MAX_POINTS to determine the maximum allowed characteristic points for your system (typically 16384 or 32768 depending on NCK memory configuration).
- 2
Check axis-specific MD $AA_QEC_COARSE_STEPS and $AA_QEC_FINE_STEPS values. Calculate: ($AA_QEC_COARSE_STEPS+1) × $AA_QEC_FINE_STEPS. If MD $AA_QEC_DIRECTION_DEPENDENT is set to 1, double this product. Compare against $MA_MM_QEC_MAX_POINTS.
If direction-dependent QEC is active, memory requirement doubles—verify via MD $AA_QEC_DIRECTION_DEPENDENT = 0 or 1.
- 3
Reduce either $AA_QEC_COARSE_STEPS or $AA_QEC_FINE_STEPS to lower the total characteristic point count. For example, decrease $AA_QEC_FINE_STEPS from 16 to 8, recalculating the product to remain below $MA_MM_QEC_MAX_POINTS.
- 4
If direction-dependent compensation is not essential, set MD $AA_QEC_DIRECTION_DEPENDENT = 0 to halve memory consumption. Recompile and transfer the QEC characteristic curve data ($AA_QEC_POLY_COEFF array) to the NCK, then reset the axis alarm.
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