In-process monitoring during laser beam welding

Abstract

One reason for the increasing use of laser welding in various industries is the enhancement of economic efficiency compared to competing techniques. To utilize this advantage automated process control strategies are required. One established method of in-process monitoring during laser beam welding is the use of single detectors like photo diodes to analyze the process emissions in different spectral areas. Another method is the use of cameras for the spatially resolved analysis of the emissions.Using a camera during laser welding of steel and aluminium the main difficulties are on the one hand the optical resolution of the large temperature range from the melting to the evaporation point, on the other hand disturbances by the radiation of the excited metal vapour above the work piece. Because of the higher optical dynamics and the possibility of direct pixel access CMOS cameras are preferred to CCD cameras for the process monitoring tasks.Experiments regarding the in-process monitoring at different spectral areas show the influence of the selected wave length on the detection results. Furthermore the experiments show that the reliability of the process control systems can be increased by a combination of single detector and camera based methods.One reason for the increasing use of laser welding in various industries is the enhancement of economic efficiency compared to competing techniques. To utilize this advantage automated process control strategies are required. One established method of in-process monitoring during laser beam welding is the use of single detectors like photo diodes to analyze the process emissions in different spectral areas. Another method is the use of cameras for the spatially resolved analysis of the emissions.Using a camera during laser welding of steel and aluminium the main difficulties are on the one hand the optical resolution of the large temperature range from the melting to the evaporation point, on the other hand disturbances by the radiation of the excited metal vapour above the work piece. Because of the higher optical dynamics and the possibility of direct pixel access CMOS cameras are preferred to CCD cameras for the process monitoring tasks.Experiments regarding the in-process monitoring at different spect...