Joining with Versatile Friction-Spun Joint Connectors

Abstract Mechanical joining techniques such as riveting and clinching are specifically designed on the basis of the joint’s properties i.e. the geometry, dimensions, loads and materials employed. These design guidelines result in an ever-greater variety of joining-technique versions and related components, such as rivets and fasteners, as increasing importance is attached to lightweight design and hence to the processing of various pre-products. This trend is resulting in a high cost for the engineering, tooling, machine and set-up time. SFB TRR 285, which is being funded by the DFG (German Research Foundation), is focusing on this issue in its research work. The research goal is the development of a methodology for versatile process chains for mechanical joining. The LUF (Chair of Forming and Machining Technology) is involved in this special research area and is investigating joining with versatile friction-spun joint connectors. This article presents an innovative joining technique employing versatile friction-spun joint connectors to bond a wide range of bulk sheet materials. Before being installed, the initial connector, which is wire/tubular-shaped at that point, is pre-shaped using the friction-spinning techniques. The forming operation as well as the joining process is performed/supported by friction-spinning. As kinematic process control characterizes friction-spinning, both ends of the connector can undergo in-process shaping to form versatile joint-specific heads employing same tools, initial connector materials and machinery. This joining technique thus includes the ability to bind different joint components with their individual dimensions, geometry and material. The method is accordingly a cost-effective solution for joining a wide range of components and significantly increases design flexibility.