Numerical model of CO2 laser welding of thermoplastic polymers

Nowadays laser welding of plastics can offer flexible seam contouring, minimal heat input, mechanical stress and consistent weld quality. Therefore the laser welding represents an alternative to conventional joining techniques for plastics. The availability of reliable numerical models can help researchers and engineers to give a better place in industrial scale situations to plastics laser welding. In this paper thermo-morphologic and mechanical behaviour of moulded thermoplastic polymers during the laser welding were simulated by means of the finite element method (FEM). Keyhole and conduction welding for butt and overlap configurations were analysed. Recrystallized zones and penetration depth were calculated for different laser welding speeds and powers. The undesired phenomenon of the polymer decomposition associated with recrystallization and thermal heating were predicted and made controllable by varying the laser power and run speed. This investigation showed that laser welding of thermoplastic polymers can be reasonable modelled by FEM both for keyhole and conduction welding conditions.