Robotic Friction Stir Welding using a Standard Industrial Robot

In the automotive industry, a barrier to widespread implementation of friction stir welding (FSW) for aluminum joining is the perceived need for high cost, custom capital machinery. The reason for this perception is that the FSW process requires relatively large forces that commonly used automation machinery (e.g. an industrial robot) has difficulty producing. Further complicating the issue, is the need to perform FSW over three-dimensional contours. This further increases the cost of custom capital equipment. Industrial robots would be a preferred solution for performing FSW for a number of reasons, including; their widespread use in the automotive industry, their ability to repeatedly follow three-dimensional paths, and their low costs. For these reasons, a project was initiated to determine the capability of an industrial robot to perform the FSW process. A FSW system was integrated to an ABB robot. Initially, the robot had little success performing FSW, but welds could be made. The implementation of a force control (rather than position control) strategy greatly improved the results. Three dimensional lap welds (2 mm to 2 mm) have been made at travel speeds between 1 and 2 meters per minute. This paper will describe the robotic FSW system. In addition, a case study will be explored that involves dissimilar thickness tailor welded blanks, where at least a five-degree of freedom system is necessary to generate welds. High integrity dissimilar thickness butt welds (1 mm to 2 mm) have been made at travel speeds approaching 2 meters / minute.