SINUMERIK 840D sl alarm 25050 during contouring, what to check?
I'm getting alarm 25050 on my SINUMERIK 840D sl during contouring moves. It happens at the same spot every time. What should I check first?
Alarm 25050, "Axis contour monitoring," on a SINUMERIK 840D sl indicates that an axis's actual position deviates from the expected position by more than the defined contour tolerance (MD36400). This typically occurs during contouring, cutting, or rapid moves with high acceleration, or when encountering an obstruction. The program is canceled, and the axis enters follow-up mode.
Likely causes and checks
1Mechanical problem
- Points to it
- A tight spot, binding, or high inertia can cause the axis to deviate from its commanded path, triggering the alarm. The alarm occurring at the same position or under load, and the axis running rough when jogged, are strong indicators.
- Check
- Inspect the machine mechanics for smooth running and verify the moving masses. Look for any obstructions or areas of increased friction.
2Position controller overshoots the setpoint
- Points to it
- If the position controller is not optimally tuned, it might overshoot the commanded setpoint, leading to a deviation that exceeds the contour tolerance. This is often seen after tuning changes or if overshoot is visible in a trace.
- Check
- Review the position-controller optimization (MD32200 Kv). The axis should follow the setpoint without overshooting. If it overshoots, improve speed-controller optimization or reduce Kv.
3Speed controller poorly optimized
- Points to it
- A poorly optimized speed controller can result in the axis not following the setpoint accurately across its travel, leading to contour errors. This would manifest as poor following behavior throughout the travel, not just at a specific spot.
- Check
- Have the speed controller re-optimized on the SINAMICS drive.
4Contour tolerance set too small
- Points to it
- If the contour tolerance (MD36400) is set too restrictively, even minor, acceptable deviations can trigger the alarm. This is usually suspected if the alarm appears after a machine data change and no mechanical or tuning faults are found.
- Check
- Consult the machine builder to check MD36400 against the archived values. Widening this parameter should be a last resort and not used to mask underlying mechanical issues.
Next check: Given that the alarm occurs at the same position every time, start by thoroughly checking the machine's mechanics for any tight spots, binding, or obstructions that could be causing the axis to deviate.
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