EDUARD ARTHUR BERGER, LIVIUS MILOS RESEARCHES CONCERNING LASER WELDING OF DIAGNOSIS AND CONTROL MODULE This article deals with weld quality in reference to strength and seal using in experiment quasi-simultaneous laser thermoplastic welding, method for PA 6.6 GF 35, base material. In laser welding of thermoplastics, sometimes referred to as „laser transmission welding” or „through transmission IR welding (TTIr)”, transparent and absorbing parts are bonded together. The laser beam penetrates the transparent plastic and is converted to heat in the absorbing plastic. Since both parts are pressed together during the welding process, heat is conducted from the absorbing to the transparent plastic, allowing both materials to melt and create a bond. Internal joining pressure is also generated through the local warming and thermal expansion. Almost all thermoplastic materials and elastomeres can be welded with the LASER beam – including ABS, PA, PC, PP, PMMA, PS, PBT, as well as glass fibre reinforced plastics. The strength of the welding seam is comparable with the base material strength.