Supportive Robotic Welding System for Heavy, Small Series Production with Non-Uniform Welding Grooves

Heavy welding is a demanding task with high robotization potential. This applies especially for the runners of Francis hydropower turbines, due to the high working costs and EHS requirements in Europe. However, heavy welding is often related to small-series production with long processing time. This sets high demands on the planning and monitoring functionality of the robot system. The research in this field is gaining momentum, yet very few articles suggest suitable solutions. This paper presents a robotic welding control system design and application that facilitates the planning, control, and monitoring of the welding process of non-uniform grooves of large-dimension joints. Its primary and unique characteristic is the simplified operator assisted programming method, where the three-dimensional path modification problem is translated into consecutive two-dimensional modifications. Therefore, reference cross-sections are created along the welding groove, where the sequence planning task of multi pass weld bead placement is performed, and to the online modifications together with the adjustments are referred. The planning, changes and process supervision are supported by the robot system to handle uncertainties along the welding groove and adaptively utilize the robot operator experience. The activities are tracked and organized to supply information for later performance enhancement and reusability between similar processes. The supportive system design is particularly suitable for advanced, large-dimension, heavy robotic welding applications. A use case is presented on a welding a runner of Francis hydropower turbine.