Optimal Design of Robotic Friction Stir Welding Industrialization Scenarios

The friction stir welding (FSW) process is an emerging manufacturing technology for aerospace structures. FSW could be an excellent alternative to traditional assembly processes because of its numerous advantages, including... [ view full abstract ]

The friction stir welding (FSW) process is an emerging manufacturing technology for aerospace structures. FSW could be an excellent alternative to traditional assembly processes because of its numerous advantages, including superior seam properties of FSWed joints, process robustness and repeatability, reduction of the assembly operation time, reduction in the aircraft weight and generation of a smooth aerodynamic profile. This process has traditionally been implemented on specialized gantry-type FSW machines. Recent investigations have demonstrated, however, that heavy payload serial industrial robots offer promising characteristics in terms of their payload, workspace and 3-dimensional capabilities for a much lower industrialization cost. Experiments have demonstrated the applicability of such motion systems to weld aerospace aluminum alloys for thicknesses typically ranging from 0.3 to 5 mm. The mechanical properties of robotically-welded seams were essentially identical to those produced using conventional production equipment.
Despite these promising results, there still exist two main challenges associated with the industrialization of the FSW process using serial industrial robots. The first limitation relates to the high process loads transferred to the serial industrial robots unwanted lateral deviations, typically several millimeters in amplitude, and loss of normality of the tool. The second limitation pertains to the inherent payload capability limit that is highly dependent on the robot configuration, making the task of designing robotic FSW scenarios for complex aeronautic components a very tedious task.
In this presentation, the authors will present a series of developments performed at the National Research Council of Canada to design industrial robotic FSW scenarios with enhanced operational windows in force capability. Several industrial applications will be presented, including the design of a robotic FSW scenario used to assembled a large double curvature helicopter component comprising FSW seams in both lap and butt joint configurations.