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Abstract: A flexible method of forming circumferentially variant wall thickness distributions on the same shape is attempted using two oblique sheet spinning processes. The fundamental strategy entails the inclination of the flange plane of the workpiece during forming. In one type of synchronous dieless spinning, edge-hemmed aluminum blanks are formed for truncated cone shells, by synchronizing the motion of the spherical head roller in the axial and radial directions with the angle of the general purpose mandrel fixed on a bidirectionally rotating spindle. On the other hand, in the other type of force-controlled shear spinning, flat aluminum discs are formed by feeding perpendicularly to the flange plane of the workpiece and maintaining the thrust force along the plane via the roller tool, exerted onto the rotating truncated-cone-shaped die. The estimated wall-thickness distribution based on a simple shear deformation model nearly conformed to the measured thickness distributions of the products formed at several inclination angles of up to 15 degrees in the forming and both spinning methods. The low-cost value-added forming method seems to be practicable not only for metal spinning but also for other incremental sheet forming processes. [Copyright &y& Elsevier]

Abstract: This review presents a thorough survey of academic work on the analysis and application of the mechanics of spinning. It surveys most literature published in English and the most important publications in German and Japanese languages. The review aims to provide insight into the mechanics of the process and act as a guide for researchers working on both metal spinning and other modern flexible forming processes. The review of existing work has revealed several gaps in current knowledge of spinning mechanics: the evolution of the stress state and the strain history of the workpiece in both conventional and shear spinning is not well understood, mainly due to the very long solution times that would occur in modelling the process throughout its duration with a sufficiently fine mesh to capture detailed behaviour through the workpiece thickness; the evolution of microstructure, residual stress and hence springback, has not been examined—either numerically or by experiment; the failure mechanisms of spinning – fracture and wrinkling – are only partially understood, through analogy with other processes, and as yet models of the process have not made use of contemporary damage mechanics; the design of toolpaths required to make particular parts without failure remains an art, and cannot currently be performed automatically with confidence. Studies on novel process configurations in spinning have shown that great potential for innovation in spinning exists. The process has the potential to be more flexible, to produce a wider range of shapes, and to form more challenging materials. [Copyright &y& Elsevier]

Abstract: The deformation mechanism of incremental sheet forming (ISF) is examined experimentally through forming specially prepared copper sheets. Strain distributions through the thickness of the sheets are measured for two configurations of ISF: two-point incremental forming (TPIF) and single-point incremental forming (SPIF), and a comparison is made to pressing. The measurements show that the deformation mechanisms of both SPIF and TPIF are stretching and shear in the plane perpendicular to the tool direction, with shear in the plane parallel to the tool direction. Strain components increase on successive laps, and the most significant component of strain is shear parallel to the tool direction. Increasing stretching and shear perpendicular to the tool direction account for differences between the sine law prediction and measured wall thickness for both SPIF and TPIF. The observed mechanisms of SPIF and TPIF differ from a mechanism of pure shear that has previously been assumed. [Copyright &y& Elsevier]

Abstract: The distribution of equivalent plastic strain through the thickness of several AISI 1020 steel plates formed under different conditions over a smooth cylindrical mandrel using a single-roller forward flow forming operation was studied by measuring the local micro-indentation hardness of the deformed material. The equivalent plastic strain was higher at the inner and outer surfaces and lowest at the center of the workpiece. Empirical expressions are presented which describe the contribution of the roller and mandrel to the total local equivalent plastic strain within the flow formed part. The dependence of these expressions upon the thickness reduction during flow forming is discussed. [Copyright &y& Elsevier]

Abstract: An experimental study is conducted to survey the technological possibility of the shear spinning of truncated hemispherical shells with a cylindrical mandrel for general purposes using A1050-H and A1050-O commercially pure aluminum sheets of 1mm thickness. It is found that there exist forming limits to prevent the occurrence of wall fractures and flange wrinkles during the spinning process of truncated hemispherical shells. It is also found that the sine law is not realized exactly in shear spinning of truncated hemispherical shells with a cylindrical mandrel for general purposes due to the spring back of the workpiece. [Copyright &y& Elsevier]

A high quality of cone surface finish was achieved by carefully controlled over-roll thickness in the shear spinning process. In this study, blank thickness, roller nose radius, mandrel revolution, roller feed and over-roll thickness were taken as major process variables to investigate the effects of the above parameters on the surface roughness of cone shape products. From the experiment, several sets of experimental data were obtained, which in turn were used to construct regression equations for applied forces and product surface roughness. The results were verified by four extra spinning experiments. It is found that deeper over-roll combines with the thinner blank sheet, larger roller nose radius and slower roller feed, and are advantageous for obtaining smoother surface roughness. Over-roll of the blank in shear spinning is an effective way to improve the surface roughness of the product. [Copyright &y& Elsevier]