Siemens SINUMERIK 840D sl / ONE alarm 25050: Axis contour monitoring
Alarm 25050 “Axis %1 contour monitoring” on a SINUMERIK 840D sl means the axis’s true actual value differed from the actual value the NCK expected from its internal model by more than MD36400 $MA_CONTOUR_TOL. The program is cancelled, the axis goes to follow-up mode and the alarm clears with RESET.
Diagnose this with AI
Try Free CNC Alarm Diagnostic Upload a keypad photo, the fault history or a parameter export from your Siemens SINUMERIK 840D sl / ONE. InduQT compares the evidence and suggests the next useful checks.
When it happens
- Contouring and cutting moves
- Rapid moves with high acceleration
- Moves into a hard spot or obstruction
Likely causes and checks
1Mechanical problem: tight spot, binding or high inertia
- Points to it
- Alarm at the same position or under load; axis runs rough when jogged.
- Check
- Check the mechanics for smooth running and the moving masses, as Siemens lists.
2Position controller overshoots the setpoint
- Points to it
- Alarm after tuning changes; overshoot visible in a trace.
- Check
- Check position-controller optimization (MD32200 Kv): the axis should follow the setpoint without overshoot; otherwise improve speed-controller optimization or reduce Kv.
3Speed controller poorly optimized
- Points to it
- Following behaviour poor across the travel, not at one spot.
- Check
- Have the speed controller re-optimized on the SINAMICS drive.
4Contour tolerance set too small
- Points to it
- Alarm after a machine data change; no mechanical or tuning fault found.
- Check
- Have the machine builder check MD36400 against the archive; widening it is a last step, not a fix for a mechanical fault.
Telling it apart
- 25040 is checked after motion has ended (standstill); 25050 during motion.
- 25060 speed setpoint limitation means the drive was asked for more speed than MD36210 allows for longer than MD36220, often from a load surge or obstacle.
- If 25201 drive fault or SINAMICS alarms come with 25050, the drive stopped following and those alarms are the starting point.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| MD36400 $MA_CONTOUR_TOL | Contour monitoring tolerance | Allowed difference between modelled and actual position. |
| MD32200 $MA_POSCTRL_GAIN | Position loop gain (Kv) | Overshoot with too high a Kv, or poor following with poor speed-loop tuning, both trip contour monitoring. |
Evidence to collect
- Axis name, position and feed at the alarm
- Trace of setpoint vs actual position if available
- MD36400 and MD32200 vs the builder’s archive
- SINAMICS alarms at the same time
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