Modified cross-wedge rolling to creating hollow shafts

Cross-wedge rolling (CWR) is an incremental forming method for producing rotationally symmetric components such as a basic shape of gear shaft or a preform before impression die forging.In CWR the material of a solid cylindrical billet is redistributed in axial direction while the billet diameter is reduced. Conventional CWR cannot be used to produce hollow shapes. This paper presents a modified CWR process, which enables the manufacturing of hollow shafts and thus provides a technological base for utilizing the large potential of the method regarding cost and resource efficiency in mass production. The method introduces two mandrels which act concurrently with the tooling wedges in an elaborate kinematic system. During processing, the generated shear stresses induce fracturing located along the billet axis. The actively driven mandrels use the fracture and penetrate axially into the workpiece. This paper provides a description of the basic principle of this innovative method and discusses the complex interaction between tool geometries, kinematic system and processing parameters