Laser beam positioning in quasi-simultaneous laser transmission welding of polymers

Abstract

Laser transmission welding (LTW) technology is widely used in the automotive, medical, electronic device industries, and for joining complex polymer assemblies. LTW offers unique advantages in weld quality and mechanical properties compared to conventional polymer welding processes [1][2][3][4][5][6].LTW performance depends on material properties, process parameters, laser irradiation, and application strategies. Various laser irradiation strategies have been developed and implemented in laser welding, varying in laser scanning techniques, cycle times, and process flexibility. Welding is influenced by the laser irradiation methods that define the process capabilities, including weld profile, part size, part variety, and cycle time. The four main variations of LTW are contour, simultaneous, quasi-simultaneous, and mask welding techniques [2-4]. In the contour LTW technique, the laser beam moves along the predefined weld path to form the weld, being the simplest LTW variant. In simultaneous laser welding, the joint is achieved using a precise arrangement of laser diode modules that simultaneously irradiate the entire weld contour. The joint configuration can be welded using special beam-shaping diffractive optical elements (DOE), avoiding the complex arrangement of laser modules along the laser weld contour. In the quasi-simultaneous laser welding (QSLW) technique, the laser beam passes through the parts to be welded several times at very high speed. By using the galvo mirror system, the laser beam is directed according