Methodological comparison of laser stripping solutions with contemporary pulsed lasers for e-drive copper hairpins

The electric drives used in traction applications employ conventionally pure Cu bars bent to the required form, inserted in the stator and welded by a laser at the extremities. These extremities, which are referred to as Cu hairpins, should be stripped off from the electrically isolating polymeric enamel. Laser stripping is industrially used to remove the enamel from the Cu surface. Pulsed wave lasers are employed for the purpose with a large variety of solutions industrially available to the end users. The peculiar process may give way to material removal by surface heating for instance using infrared radiation (IR) or ultraviolet (UV) lasers or an indirect material expulsion via near-infrared (NIR) sources. Accordingly all major laser sources, namely CO2, active fiber, active disk, and Nd:YAG at different wavelengths, may be used for the purpose. Such laser sources possess very different characteristics regarding the pulse durations, power levels, and beam diameters. As newer laser system solutions are made available, the need for methods and experimental procedures to compare the process performance also increases. This work compares 7 different hairpin stripping solutions based on contemporary pulsed laser sources along with a detailed comparative analysis method. Initially, the 7 laser sources are used for hairpin stripping. The process quality is analyzed through surface morphology, chemistry, and the mechanical strength upon laser welding. Productivity and efficiency indicators are collected. Using the collected data, the work proposes system configurations for three different scenarios prioritizing quality, productivity, and cost.