Machine vision system for online weld pool observation of gas metal arc welding processes

At the Welding and Joining Institute of the RWTH Aachen University, an optical sensor system which allows the online observation of weld pools when utilising gas metal arc welding (GMAW) processes has been developed. Moreover, an image processing software has been created which provides information about the actual weld pool width as well as the actual position of the gap in relation to the position of the wire electrode. This supplemental process information makes it possible to deduce the width of the resulting weld and the extent of the potential misalignment of the welding torch. One key requirement of the developed system and its algorithms was the assurance of a defined time constraint. If this is given, the GMAW process can be adapted to potential disturbances so that the desired weld quality can be achieved. The system has been successfully tested on typical groove preparations, like fillet welds, butt joints and V-joints. This paper focuses on the setup and the functionality of the machine vision system and the challenges of gaining usable information with simple, fast and reliable algorithms.