3D friction stir welding with a cost-efficient machine concept at Fraunhofer IWS

The increasing demand of cost efficiency and lightweight design can be considered as major drivers for the introduction of new materials and material combinations in the aircraft industry. Consequently new joining technologies and welding approaches are needed. Friction stir welding is one of these new joining technologies and can help to overcome typical welding problems, which are present when fusion welding or similar melting based welding technologies are enabled for hard to weld alloys or mixed material joints. This technology offers a great potential, when new aluminum alloys or even dissimilar alloys have to be joined together. Fraunhofer IWS has been working on friction stir welding for several years. The introduction and enhancement of a cost-efficient parallel kinematics concept, a so-called Pentapod, is the basis for several studies on the field of friction stir welding. With a great space to working space ratio and its five-axis processing capabilities, this versatile machine concept is appropriate for welding parts with a great variation in size and shapes as well as for joining 3-dimensionally curved weld lines. The machine was advanced with newly developed control algorithms to operate the friction stir welding process force-, torque- and position-controlled. Furthermore all milling operations for pre- and post-weld treatments can also be performed within this machine. A detailed overview about the capability and potential of the machine concept, especially in terms of potential aerospace application will be given. The research focuses on the feasibility of joining large and flexible aircraft parts, new machine concepts, 3D-welding as well as mixed material joints. Examples of recent projects which have been conducted by utilizing the parallel kinematics concept will be given. Friction stir welding of tailored welded blanks made of AlMgSc, the welding of aluminum die casts and 3D applications like the welding of gear box will be given. In addition to these examples a detailed survey of mixed material joints, like friction stir welded aluminum to copper joints and aluminum to steel joints will be presented.