Smart Laser Welding and Monitoring of Sheet Materials

摘要

Advanced technologies are presented that contribute to the efficient automated laser welding of sheet materials for the car industry. High speed and accurate laser vision cameras are used on-line to track and inspect weld butt joints of thin galvanized steel sheets at speeds up to 15 m/min, such as for tailor welded blanks. High definition dual field laser triangulation cameras inspect car roof brazed joints. A new Laser Process Control System is proposed as an option to the laser tracking and inspection system. This LPCS integrates a coaxial pyrometer and a back reflection sensor in the laser head for online monitoring of the thermal radiation of the molten pool - keyhole area, and of the back reflection of the power laser from the work piece. Temperature and back reflection monitoring can identify the conduction and keyhole welding modes, the keyhole saturation temperature, as well as any perturbation of the keyhole leading to welding defects. The paper presents several illustrated examples of laser welding, monitoring and defect detection using powerful integration of simultaneous real-time information provided by radiation sensors and laser scanning of joint and weld bead. New trends will also be outlined in monitoring newer laser welding processes, such as plastic sheet laser welding, robot and scanning laser welding.