Evaluation of current welding robot and improvement proposals for future use

Abstract: Welding of elements, a heat exchanging component, is one of the most essential processes during the manufacturing of Tubel evaporators. Weld joints consists of fillet welds of thin tubes against a plate on one end, and on the other end against a thicker pipe with entry holes for the tubes. Since earlier a welding robot station has been invested to the production line to improve manufacturing quality and productivity. The results from the robot welding hasn’t been reliable enough though, and have led to additional operations to fix the problems that has occurred.This thesis project has the objective to investigate and analyse the problems occurred from earlier use of the robot station. The main challenges of the process have been identified and key factors that influence the welding performance are recognised to fully understand the problem. A list of improvement actions has then been proposed by first hand considering in terms of quality and productivity. The improvement actions are then evaluated by test welding.Materials used in the component and during test welding are either duplex or austenitic stainless steels, which weldability differs significantly between these. Related discontinuities and defects are similar for both material, but occurrences of these are higher when welding duplex steels.Improvement actions has included positioning of the electrode, parameter optimization, modification of robot equipment, base material improvements and welding sequence. Results of welding austenitic steels was considerably better and showed good results after the test welding, while welding of duplex steel likely needs design modification of the component to satisfy quality requirements and standards.