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Infeed rotary swaging is a cold forming production technique to reduce the diameter of axisymmetric components. The forming is achieved discontinuously by a series of radial strokes that are spread over the shell of the part. Due to tolerances within the rotary swaging machine, these strokes perform individually and the resulting stroke pattern is not homogeneous with regards to circumferential and longitudinal distribution. Nevertheless, in combination with the high number of performed strokes and the large contact area between the dies and the part, the external part properties, such as diameter, roundness and surface roughness, show even values along the finished part. In contrast, strength-defining internal part properties, like microstructure and residual stress components, are more sensitive to the actual pattern and temporal sequence of the individual strokes, which is investigated in this study. The impact of process fluctuations during the conventional process, which are induced by the tolerances of machine tool components, was verified by numerical simulations, physical tests and measurements of residual stress distributions at the surface and at depth. Furthermore, a method is introduced to maintain the stroke following angle ∆φ at zero by flat dies, and thus the actual pattern and temporal sequence of the strokes was homogenized. The results show that the residual stress fluctuations at the surface could be controlled and reduced. Furthermore, it is demonstrated that the depth profile of the residual stresses at a distance of 300 µm from the surface developed independently from the process fluctuations.

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Rotary swaging is a well established cold forming process e.g. in the automotive industry. In order to modify the material properties by swaging systematically, a new process of swaging with asymmetrical strokes of the forming dies is investigated. The newly developed tools feature flat surfaces and do not represent the geometry of the formed part as in conventional swaging. Numerical simulation and physical tests are carried out with special regard to the resulting geometry, mechanical properties and the microstructure. During these tests copper wires with diameter d0=1 mm are formed. Regarding the microstructure in the longitudinal section of formed specimens, elongation of grains in the central part and grain size reduction in the boundary area are observed. Furthermore, this approach opens up new possibilities to configure the geometry of wires. 2D-simulation is applied and discussed in the paper to investigate change of the processed geometry (cross-section) and shear strain distribution during the rotary swaging process.