Analysis of YAG laser lap-welding of zinc coated steel sheets

Joining of coated steel sheets in an overlap configuration today has become an important manufacturing step in automotive production. But the assembly of functional structures using laser welding processes deals with several challenges. This paper presents a new approach to join coated steel sheets by using a fast frequency modulation of the laser power according to actual process states. Based on the analysis of optical process emissions, a control system is applied. Experimental results point out the interference of process oscillations with the external influence. They show that a well-directed control of the welding process reduces its partially chaotic behaviour.