A method is provided for welding a ball to another component. The method includes: providing a sonotrode which has a trough-shaped recess, in particular a spherical cap-shaped recess; pressing the ball against the other component by the sonotrode, the ball protruding into the trough-shaped recess; and vibrating the ball by the sonotrode such that material of the ball and/or material of the other component melts, and the ball is welded to the other component.

A method is provided for producing a component connection. The method includes the following steps: providing a first component, providing a first ball, pressing the first ball against the first component by a sonotrode, vibrating the first ball by the sonotrode such that material of the first ball and/or material of the first component melts, and the first ball is welded to the first component, providing a second ball, pressing the second ball against the first ball by the same sonotrode or another sonotrode, and vibrating the second ball by the same sonotrode or the other sonotrode such that material of the second ball and/or material of the first ball melts, and the second ball is welded to the first ball.

A method is provided for producing a component connection. The method includes the steps of: providing a first component that is made of a thermoplastic plastic material at least in the region of a portion of the surface thereof; providing a ball that is made of a thermoplastic plastic material in at least one region of the surface thereof; pressing the ball on the first component such that the thermoplastic plastic material of the ball comes into contact with the thermoplastic plastic material of the first component; vibrating the ball using an ultrasonic sonotrode and welding the ball with the first component; providing a second component having a through hole; bringing the second component to the first component in such a way that the ball projects at least into the through hole of the second component or a portion projects to a certain extent through the through hole; clipping a clip element to the ball, wherein the clip element projects beyond the through hole and joins both components to one another in an interlocking and/or force-locked manner.

Disclosed is a tool (10) for welding a workpiece (21) by means of friction welding, in particular by means of ultrasound, wherein the tool (10) has a working surface (5) which contains at least one, preferably several, grooves (6). The working surface (5) has a curvature. The invention also relates to a method for welding a workpiece and a welded workpiece.

Two workpieces 30, 40 are joined by means of ultrasound. First, a workpiece 30 with at least one energy direction sensor 31 and a second workpiece 40 are provided. The workpieces are brought into contact with each other in such a way that the energy direction sensor 31 comes into contact with a first surface 41 of the second workpiece 40. Ultrasonic vibrations are then introduced into one of the workpieces 40 via a working surface 11 of a sonotrode 10. A sonotrode 10 is used, which has a contour with contact lines 12 on the working surface 11. The sonotrode 10 is positioned with respect to the first workpiece 30 in such a way that the contact lines 12 run transversely to the energy direction generator 31.