Development of a new adaptive spot weld controller driven by an ultrasonic monitoring system.

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Ranging from 4000 to 6000 spots for each single vehicle, resistance welding still plays a vital role in any automotive body structure construction, and it is directly related to the passenger safety rates. Despite being a major joining technology in automotive industry for decades, the fast-paced environment of a body shop still misses some vital information in terms of process quality and monitoring, which nowadays is a severe demand from the Industry 4.0 standards. The "adaptive" welding controllers were designed to fill this gap, but it seems that current process monitoring technologies have reached a limit in terms of their capacity to increase the detection rates, as well as the ability to promptly react to any disturbance in the regular welding process. Also, the increased use of new materials in automotive bodies, such as high strength steels and aluminum alloys, also brings some challenges, since its welding behavior tends to be more unstable compared to the conventional steels usually applied. In recent years, the Institute for Diagnostic Imaging Research (IDIR) at the University of Windsor has developed a state-of-the-art quality monitoring technology using ultrasound. A piezo-electric sensor, built into the welding electrode, is working to send sound waves into the welded sheets and receive the reflections from the internal structure of the joint. It allows the determination of when the melting begins and what are the main dimensions of the weld. In this sense, a solution with a high probability of success involves the use of both techniques combined: ultrasonic sensors placed inside the welding gun, triggering the decision-making algorithm from the adaptive welding controller. This solution will be a breakthrough development, since it will realize the "built in quality" concept, providing a significant increase in the assembly process fault(s) detection rates, as well as an immediate feedback to the weld controller, which will be able to apply the proper corrections of the weld parameters in real time, making it possible to implement the "zero defect" concept.