CAD / CAM Welding Robot System in Steel Bridge Panel

Recently, the serious problems facing heavy industries such as the increase in the average age of employees, shortage of skilled workers and environmental problems in the workplace are being addressed. The bridge panel fabrication system we have developed is such an approach to solve these problems. It consists of two parallel box girder panel sub-assembly lines, one exclusively for web panels and the other for flange . Each line is made up of stages for fitting, welding , re-forming, drilling and finishing. All of the line equipment is controlled by the line computer in the central control room. The box girder panel is reinforced by the stiffeners and the fillet welding is the objective of each welding stage. In total, 14 articulated-type arc welding robots are applied in the welding stages. In the web panel welding stage, 8 robots are hung from stationaly transverse girders with 2 m span in longitudinal direction and can be used for operations up to 4 m wide by 16 m long. In the flange panel welding stage, 2 welding robots are hung from each of the 3 transverse sliding units that are arranged under the mobile gantry . In total, 6 welding robots cover the 5 m wide by 16 m long work area . By adopting the High Speed Rotating Arc welding process, we have doubled welding efficiency as compared with conventional processes. Furthermore, this process is more effective to reduce panel deformation because of the lower welding heat input. The welding robot system is stabilized with precise accuracy by newly developed joint end and bead end sensing techniques as well as a seam tracking arc sensor system based on the High Speed Rotating Arc. All of the welding robot is linked with LAN to the newly developed, teachingless CAD/CAM system that is based on the computerized design fabrication system for bridge fabrication. This system is especially effective for bridge panel fabrication where almost all the panels are of different shapes. Thus, a step towards computer-integrated manufacturing (CIM) in steel structure fabrication has been achieved.