The master's thesis shows the study of the seam tracking in the robotic CMT welding. There are different systems on the market. On our welding product it is necessary to provide quality joints, otherwise, injuries or even death of the product users can be caused. Unsuitable welds come due to different thickness or chemical changes of the base materials, resulting in welding parts with different geometries. With welding control sensors, we ensure the proper movement of the robotic torch and the use of correct welding parameters. By doing this we ensured that the weld penetration is good and consequently the weld has acceptable mechanical properties. Due to a series production, it is necessary to make a cost estimate of the savings that occurs when using the system. We saved on rework of pieces, which we performed manually. In master thesis we shows the mechanical properties of welds, which were welded by the welding control system and the comparison with samples where the welding control system was not used. It has been found that we get deeper penetration in base material and greater root height of the weld if we use adaptive welding.