Patent ID: 8584343

Claim:
A method for attaching a joining element to a deformable flat material, the joining element comprises on a bearing surface of a joining element body, a rivet section protruding over said bearing surface, wherein an attachment of the joining element on the deformable flat material takes place in a joining and riveting process by insertion of the rivet section into a joining opening and by permanent deformation of the rivet section to form a rivet collar engaging behind the joining opening so that the deformable flat material is held under tension in an edge area surrounding the joining opening between the rivet collar and the bearing surface of the joining element, wherein during the riveting process a dome-shaped section forming a recess for accommodating or receiving the rivet collar is produced, wherein the riveting process is performed by use of a tool having on one side of the deformable flat material an axially movable punch-shaped first tool part with a cone-shaped section on a face and having on an other side of the deformable flat material an axially movable punch enclosed by a die-shaped second tool part receiving the joining element with the joining element body during the riveting process, the method further comprising: inserting the rivet section into the joining opening and transforming the rivet collar with the cone-shaped section of the first tool part into a pre-formed rivet collar and keeping the deformable flat material flat in an area of the joining opening, pre-forming the dome-shaped section by deformation of the deformable flat material in an edge area surrounding the joining opening after forming of the pre-formed rivet collar, by the pre-formed rivet collar bearing against the cone-shaped section of the first tool part, and final riveting of the joining element on the deformable fiat material using the tool, the deformable flat material is clamped between the first tool part and the second tool part, such that the deformable flat material in the edge area of the joining opening is clamped between the rivet collar and the bearing surface, wherein for pre-forming the dome-shaped section, the joining element bearing against the punch is axially moved relative to the deformable flat material with the pre-formed rivet collar bearing against the cone-shaped section of the first tool part, and wherein for the final riveting of the joining element, the punch bearing against the joining element body is moved toward the first tool part, causing the deformation of the pre-formed rivet collar to form the final rivet collar.