Online Control Sensors for Welding Processes Based on Optical Recognition

: In the automotive industry, laser welding processes increasingly replace conventional welding methods. The remaining flaw rate of the final product has to be below 5 parts per million (ppm). Therefore, the demands on quality control systems are correspondingly high. Only a combination of sophisticated plasma monitoring, power measurement, and image processing techniques can reliably maintain such low residual flaw rates in production. Plasmo™*** is a modular system for automated online quality control of continuous wave laser welding and brazing processes widely used in the automotive industry. An overview of the features and physical background of the plasmo™ system is presented, and its capabilities are demonstrated in a representative example. The standard algorithms and signals in the time domain for online detection of failures and flaws are outlined, as well as new algorithms for special laser welding processes, like e.g. pulsed Nd:YAG laser welding, laser brazing. The potential and capabilities of time series analyses of the process signals are discussed.