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Siemens SINUMERIK Controller
Program/G-code · Intermediate · 30-120 minutes
Siemens 61709 - Cutting edge radius too small
Alarm 61709 indicates the NCK contour calculation engine exceeded its time budget while processing a CNC program block, typically during CYCLE950 execution. This occurs when the interpolation and geometry computation cannot complete within the configured cycle time, causing the real-time kernel to force a timeout exception.
61709
Siemens 61709 - Cutting edge radius too small
Cutting edge radius too small
Control reaction: Interpreter stop NC Start disable in this channel. Interface signals are set. Alarm display.
Root Cause Summary
Alarm 61709 indicates the NCK contour calculation engine exceeded its time budget while processing a CNC program block, typically during CYCLE950 execution. This occurs when the interpolation and geometry computation cannot complete within the configured cycle time, causing the real-time kernel to force a timeout exception.
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 Diagnostics > NCK > IPO menu and verify cycle time parameter MD10020 (IPO cycle time in milliseconds). Standard values are 8ms or 16ms. Document current setting.
- 2
Check CYCLE950 program block complexity: verify spline order (MD31010, MD31011), tool radius compensation mode (MD20210), and feed rate. Reduce spline degree or segment complexity if excessive.
Decreasing IPO cycle time below hardware capability (MD10021) may cause system instability.
- 3
Monitor actual NCK load via Diagnostics > System Load indicator. If consistently >85%, reduce concurrent axis motion or offload geometry pre-computation to CAM.
- 4
Review ServiceData SD43325 (Contour calculation timeout threshold) if available on your firmware version; increase conservatively by 10-20% only if justified by part complexity.
Excessive increases mask underlying performance issues and reduce real-time responsiveness.
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