TwinCAT NC Error 0x4550 (17744) on an axis during acceleration, what to check?
I'm getting a TwinCAT NC Error 0x4550 (17744) on one of my machine's axes. It happens during acceleration or at high speed, and the axis stops immediately. What should I check first?
The TwinCAT NC Error 0x4550 (17744) indicates that the position lag error exceeded the Maximum Position Lag Value for longer than the Maximum Position Lag Filter Time. This fault typically occurs during acceleration, at high speeds, or when the axis encounters a mechanical obstruction or load change. The NC axis is immediately stopped and set to an 'Error' state.
Likely causes and checks
1Mechanical obstruction or binding
- Points to it
- The axis may be encountering a mechanical obstruction, a brake that isn't fully released, or binding. This causes the actual velocity to drop while the lag error grows, and the drive's torque may reach its limit.
- Check
- Trace set position, actual position, lag, and torque in Scope View. Visually inspect the axis mechanics and the brake for any issues.
2Motion profile exceeds drive/motor capacity
- Points to it
- The commanded acceleration or velocity may be too high for the motor or drive to follow. This often results in lag peaks during acceleration ramps and the drive reaching its current limit.
- Check
- Compare the commanded acceleration and velocity values with the specified capacity of the motor and drive.
3Scaling, encoder, or tuning error
- Points to it
- Incorrect encoder scaling, an encoder direction error, or an issue with the position controller tuning can lead to this fault. The lag might grow steadily even with slow movements, or the axis could run in the wrong direction.
- Check
- Verify the encoder scaling, direction, and the position controller settings against the original commissioning values.
Next check: Start by checking for mechanical issues, as this is the most common cause. Use Scope View to trace the set/actual position, lag, and torque to gather more diagnostic information.
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