Process control of gas metal arc welding processes by optical weld pool observation with combined quality models

At the Institute of Welding and Joining Technology at RWTH Aachen University, an optical sensor system has been realized which allows the online observation of the weld pool while the process is executed. Therefore, an image processing software has been developed which provides information about the actual width of the weld pool as well as the actual position of the gap in relation to the position of the wire electrode. With this process information, the resulting width of the weld and the width of the misalignment of the welding torch can be deduced. These data shall be used to adapt setting parameters at the occurrence of deviations to guarantee a consistent weld geometry and position. On the one hand, it will be illustrated how information about the weld width can help to improve and simplify quality models. On the other hand, the weld width obtained by image evaluation will be correlated to real macro-sections and the adjusted values will be used as input for a calculation of further geometry parameters. Associated with setting parameters like welding speed and wire feed speed, these information provide the basis for quality models which are used to control and supervise the process.