Product Code: ICAL06_P502

The Effect of Parameter Changes in CO2 Laser Welding on Spectra
Authors:
Anna Fellman, LUT; Lappeenranta Finland
Antti Salminen, Lappeenranta University of Technology, Department of Mechanical Engineering, Laser processing laboratory; Lappeenranta Finland
Birgitta Martinkauppi, University of Joensuu, Department of Information Technology, InFotonics Center; Joensuu Finland
Jouni Hiltunen, University of Joensuu, Department of Information Technology, InFotonics Center; Joensuu Finland
Ville Heikkinen, University of Joensuu, Department of Information Technology, InFotonics Center; Joensuu Finland
Markku Hauta-Kasari, University of Joensuu, Department of Information Technology, InFotonics Center; Joensuu Finland
Presented at ICALEO 2006

The use of laser welding is evermore increased in metal industry. Laser welding processes are high productivity processes causing the bottle neck of the production usually to locate in the quality inspection after welding. In order to delete the bottle neck the use of automatic monitoring equipment has increased. These systems are able to identify the changes in the process but are not always able to identify birth of different weld defects. The monitoring equipments usually measure the intensity of the electromagnetic spectra in a wavelength range defined by the manufacturer of the equipment. The reason for the poor ability to identify defects might be caused by the principle of measurement of integrated intensity of a wide range of spectra. If the defects could be identified, it would be possible to control the process on-line giving also a possibility for closed-loop control and adjustment of the process. In this study on-line spectroscopy was used to measure the effects of parameter changes in CO2 laser welding process into the intensities of wavelengths in range of 300-1000 nm were measured. The resolution of measurement was 1 nm and measurement frequency was 50 Hz. The material welded was mild steel of thickness 6 mm and the joint type was butt joint. It was possible to see that the variations in welding parameters and groove preparation affect the spectra, changing its level and the shape of it.