Potential of robotic friction stir welding using the example of aeronautics

Friction stir welding (FSW) constitutes an innovative joining process since, amongst other characteristics, even aluminium alloys which are not regarded as fusion-weldable can be joined with a high weld quality. Special welding installations requiring a high need for investment are frequently set up in order to be able to provide the high downforces necessary for the process. However, for low weld penetration depths up to approx. 5 mm, these forces are in an order of magnitude in which industrial robots may also be suitable for this task. An FSW system which was set up within the framework of the "RoboFSW" project and had modified basic axes can now apply process forces of up to 10 kN which are sufficient for a wide spectrum of applications for friction stir welding tasks. On the basis of tests, it was possible to show that a constant weld quality can even be produced in different working positions and on curved surfaces. The repercussions of the process forces on the robot cause the tool path to deviate from the programmed nominal path. However, this can be tolerated within certain limits. As a result of the planned integration of a seam tracking system, it should be possible to correct these deviations during the welding operation. In the short and medium terms, the objectives are to use the robot for the welding of large-area components relevant to aeronautics and to assess the abilities of the robot to weld contours with excessive curvatures.