Possibilities for online process monitoring at laser brazing based on two dimensional detector systems

Abstract

Laser brazed seams are nowadays well established in automotive industry for joints which must fulfill high quality standards. Joints located in direct visible areas of the car body, like the connection between roof and side-panel or the trunk-lit, must be manufactured without any failures like pores or spilling. To achieve this goal, system technology is subject to high accuracy requests on the one hand; on the other hand the seams are controlled after manufacturing either manually or by optical systems. In contrast to laser welding there are no online process monitoring systems available for laser brazing until now. The following investigations reveal some possibilities to monitor the laser brazing process of zinc coated steel sheets by two dimensional detector systems. For this purpose two different spectral intervals are chosen. With the help of images in the visible spectrum for instance the quality of the wetting process and the formation of fusion failures can be observed. The investigations in the near infrared spectrum reveal phenomena caused by an imbalanced temperature field, which are the basis for failures in laser brazing.