Laser welding of thermoplastics: An overview on lasers, materials, processes and quality

•Main lasers used in thermoplastic welding.•Description of the main thermoplastic laser welding techniques.•Description of the principal operating variables of the process.•Description of the key welding quality assessment techniques. This paper offers an overview on the laser welding techniques for thermoplastic materials. The emphases are on four major aspects of the laser welding of plastics: (a) the laser systems, (b) thermoplastic materials, (c) process parameters and finally (d) characterization methods for materials and welded parts. The review focuses mainly in Laser transmission welding, including some technological variants. After an introduction to the laser welding fundamentals, the absorber-based laser transmission welding is described first. This is followed by absorber-free laser welding. The thermoplastic materials most used in laser welding are then reviewed and discussed, with focus on both welding parts of the same material and welding parts of dissimilar materials. Subsequently, the several laser welding processes or techniques are discussed. The next section discusses the main control variables or process parameters and their effects, including the effects of polymer compositions and pre-welding conditions on the laser welding process. Finally, several characterization techniques that are used to evaluate the weld quality are discussed.