Transmission laser welding of thermoplastics: Influence of welding parameters and rib dimensions on the strength of welded joints

Laser transmission welding of injection moulded thermoplastics is commonly used in industrial applications such as electronic packaging, textiles, biomedical devices, windows, signs, food and medical packaging, visual displays and automotive components due to very precise control of the process parameters, including the amount of energy delivered and its location, which results in high joint quality. In this article, the influence of laser transmission contour welding parameters and geometry of welding rib on joint force is investigated. Velocity with which the laser beam moves on the sample, temperature applied, clamp force, laser beam size and number of laser passes were studied for various dimensions of the rib with rectangular and triangular cross section. Samples of different thermoplastic materials, PMMA and PC/ABS, were produced and then joined by transmission laser welding and after that were subjected to tensile tests, in order to measure strength of the joint between the plastic parts. Initially, optimal welding conditions were found for each studied rib and their influence on the force of the joint was analysed. Afterwards, a comparison between the best results obtained for each rib was performed, in order to define the dimensions of the rib that result in the highest joint force. It was observed that samples with triangular ribs achieved higher joint strength. For both studied geometries of rib cross section, an increase of the width of the ribs improves the joint strength, while an increase of the height worsens it.