Quality Monitoring in Laser Welding of Rectangular Copper Wires for Traction Drives Using a Broadband Process Light Sensor

The electrification of vehicles poses significant challenges to automotive manufacturers, particularly in the production of electric traction drives. Winding concepts such as Hairpin, I-pin, or X-pin technology are increasingly relying on the use of rectangular copper wires instead of round wires for stator windings. Here, a large number of connection points between individual winding sections have to be realized by laser welding and are crucial for overall functionality and product quality. To ensure the quality of each of these joints, process monitoring with in-process capable sensors is increasingly being pursued. This paper focuses on whether the quality of the welds can be monitored using a broadband process light sensor. Therefore, the optical emissions of the welding plasma and the molten material are analyzed and correlations between the optical emissions and features of welding quality, such as pore formation or cross-section area, are investigated. For this purpose, the study is based on a design of experiments, which provides welds of varying quality. The study concludes that the process light sensor is suitable for monitoring the laser welding of rectangular copper wires, however establishing clear correlations between process light sensor signals and specific welding errors remains challenging and needs to be improved for enhanced industrial applicability.