Laser transmission welding of automotive headlamps without a clamping tool

A car's front headlamps represent an important design element in the automotive industry. In order to protect them from external influences, the complex lighting technology is inserted into a stable plastic housing, which is then sealed with a transparent plastic lens. The combination of the transparent lens and the black housing is eminently suitable for laser transmission welding (LTW); the numerous advantages of this technique can be exploited here, especially with regard to design. Due to tolerance compensation, it is state of the art to join automotive headlamps by adhesive bonding. In the investigations of the KTP, a prototype with a special geometry of the joining area was evolved and analyzed. Because of segmental snap-fits, which apply the necessary joining pressure, gaps can be eliminated during the welding process as a result of the setting of the lens. With this special geometry of the joining area, a clamping tool is not necessary anymore. The two parts are welded quasi-simultaneously by a laser scan system with a fast z-axis. Also, the typical material combinations (PBT+ASA GF20, PC) of automotive headlamps were analyzed by using rectangular overlap specimens and American Welding Society specimens.