Hollow lateral extrusion of tubular billets – a newly developed cold forging process

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by Dipl.-Ing. Stefan Rudolf, Institute for Metal Forming Technology (IFU), University of Stuttgart/Germany
Increased requirements in the automotive industry concerning reduction of CO2 emission require the development of new solutions concerning this aim. Hollow components are particularly suitable for this goal, especially when dealing with rotating and constantly accelerated masses. Firstly, hollow parts contribute to vehicle weight reduction and secondly, the reduction of accelerated masses has an important participation to reduction of fuel consumption. Metal forming technologies in general – and especially bulk metal forming techniques – are suitable for the production of hollow construction units for the automotive industry, as they provide economical production from medium size to a large volume number of units.
In this paper, a newly developed bulk metal forming process – the hollow lateral extrusion process of tubular billets is discussed. This metal forming process is subject of a joint project between the Institute of Forming Technology and Lightweight Construction of TU Dortmund University and the Institute for Metal Forming Technology of the University of Stuttgart. Emphasis of this work lies on development of the forming process and the required tool concept. Thus, at first the process and its characteristics are introduced and forming part geometries producible by this process are explained. Afterwards, tool concepts for different kinds of part geometries are demonstrated. Following the objective of entire understanding of proposed forming process, numerical and experimental investigations of hollow lateral extrusion of tubular billets have been conducted. Finally, conclusions will be drawn concerning such newly developed cold forging process.