Investigation on the effects of laser power and scanning speed on polypropylene diode transmission welds

Diode laser transmission welding was well established as a leading technique for industrial applications of joining plastics. The weld soundness of plastics depends on several variables like the non-isothermal crystallization, the germs growth rate, the dimensions of the heat-affected zone induced by recrystallization. Firstly, this paper proves the reliability of a numerical model based on the finite difference method at calculating the soundness variables for diode laser welding of polypropylene thermoplastic polymer. The numerical model was validated by microscopy observation of experimental polypropylene welds. Then a parametric study on the effects of the laser power and welding speed on the weld soundness variables is presented through a number of plots of the main process variables against time. The overall investigation gives a detailed picture of the influence of laser power and welding speed on the weld soundness from a microstructure point of view.