Development of laser welding process in automotive electronics industry

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Oláh István
Department of Automation and Applied Informatics

I wrote my final thesis on the subject of laser welding. The laser welding is used for different pairs of welding contacts in manufacturing of electric power steering units. In my thesis I have dealt with two major problems. One of them is that the AOI (Automatic Optical Inspection) picture recognition system cannot measure the position of the weld during the CMC (Common Mode Choke) welding, because of the varying light conditions, which are caused by the variability of the commodity. I have eliminated this issue by designing new illumination, which provides constant light conditions. The development consists of a mechanical and an electrical design. During the mechanical design I have created the holder of the illumination, which can be mounted on the laser head, and also serves as the housing of the light source. During the electric design I had to design a new light source and a control circuit, which schedules and controls the light source. The new illumination requires a cross jet system, which uses compressed air to protect the illumination and the optics of the laser head from the polluting byproducts of the welding. The other problem I had to face was that during sigma laser welding conductive particles are generated, which can get into the product and can cause short circuits. To eliminate this issue, I used parameter optimization. I was searching for an optimized parameter set in order to prevent conductive contaminations. Six Sigma method, more specifically the DOE (design of experiment) tool, was used to finalize the optimization.

The system was not only designed but also realized by producing on one hand, the PCBs for the light source and the controller, and on the other hand the mechanical parts as well. All the designed work-products were tested and installed including the mechanical parts and the circuitry. I have also tested both PCBs and I was able to validate the optimized parameters in a multi-step process to verify the results.


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