In simultaneous welding, the entire weld seam is heated and melted at the same time (i.e. simultaneously) by one or more beam sources. The arrangement of the beam sources or the beam shaping by means of suitable optical elements must be carried out in such a way that the line energy introduced during the welding process is as equal as possible over the entire weld seam. Due to the simultaneous melting of the entire weld contour and the force applied by the clamping technique, the two components to be joined move towards each other, just as in quasi-simultaneous welding, and melt is expelled laterally at the weld seam. On the one hand, the joining path serves to compensate for component unevenness, on the other hand it can also be used for process monitoring. In terms of appearance, a weld seam produced in the simultaneous welding process is in principle the same as a weld seam produced in the quasi-simultaneous welding process.