Quality assurance during laser cutting using in-situ polarisation measurement

Nowadays laser beam cutting is one of the standard methods of material processing because of its high flexibility, excellent possibilities for automation and the high quality of laser-cut parts. Laser beam cutting is also a highly dynamic process with a large number of parameters, which makes quality monitoring systems face very high challenges. Since direct observation of the processes in the cutting gap is very difficult, the thermal emissions from the cutting kerf can be used for the determination of the cutting quality during laser beam cutting. For this purpose, during laser beam cutting of steel sheets, specific beam properties of the emitted thermal radiation were recorded and processed. The emission angle of the cutting front was calculated from the obtained sensor signals by means of evaluation algorithms and is correlated with the cutting quality along the cut surfaces.

Together with students, the task was to develop a measuring system for the detection of specific beam properties of the thermal radiation emitted out of the cut kerf. The selected measurement method allowed the thermal radiation emitted by the cutting front to be detected at a high sampling rate, whereby highly dynamic processes of the melting bath could also be detected. These results can also be used to improve existing simulation models of laser cutting, as a result of which the process understanding can be extended.

To achieve these objectives three groups of students were formed. To be able to measure with a high sampling rate, a group of students developed the exactly adapted electronic circuits (for example measurement amplifiers). A further group of students adopted the recording of the sensor signals and the signal processing with the development of program modules. A third group analysed the communication interface of the robot used to read out specific process parameters and to prepare them for further signal processing.

This project has been completed.