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Various approaches to produce non-axisymmetric parts in metal spinning have been developed by researchers. In asymmetric multi-pass spinning, the motion of the roller is synchronized with the mandrel’s rotation by CNC codes to achieve oblique or non-circular shapes. In this study, cylindrical cups are formed using two kinds of oblique pass sets to investigate the effects of different parameters on thickness distribution and forming limit. In the translational pass set, the inclination angle is determined by the difference of the wall depths on two sides of the product and it is determined by the difference of half cone angles in the rotational pass set. The difference of wall thickness distribution in the translational pass is greater than that in the rotational pass and it increases as the inclination angle increases. The difference between the axial distributions on two sides of the wall decreases as the pass pitch increases near the top of the product, and it increases near the edge of the wall. A greater incremental angle does not affect the difference but reduces the uniformity of the wall thickness in the rotational pass set. All the failures are wrinkles in the experiments. Wrinkles occur when the pass pitch or the roller feed ratio is too large. A greater inclination angle reduces the forming limit in the translational pass set and does not affect the forming limit in the rotational pass set.

Various approaches have been attempted by researchers to break through the limitation of axisymmetric shape in metal spinning. In this study, a synchronous multipass spinning method for offset blanks is proposed. The motion of the roller and the rotation of the mandrel are synchronized to achieve asymmetric shapes. The roller trajectory is represented by a set of scattered data which contains the axial position of the roller, the radial position of the roller, and the rotational angle of the mandrel. Conventional spinning for offset blanks is also conducted in comparison with synchronous spinning. The geometries of the products with different offset values λ are examined. The axial distribution of wall thickness varies at different circumferential positions of the product due to the oblique shape. The thickness increases from the short side to the long side of the product. A larger offset value λ results in a larger product diameter due to the springback of the material. Forming limits in terms of roller feed ratio f, offset value λ, blank thickness t0, blank diameter D, and the number of passes are investigated. Both fracture and wrinkling occur in the experiments. Due to the oblique shape, wrinkling tends to occur during the first several passes on the long side of the flange, and fracture tends to occur during the last several passes on the long side of the product. The experiments are more likely to succeed when a small offset ratio λ, a small blank diameter D, a small feed ratio f, or a large blank thickness t0 is used. Compared with synchronous spinning, the difference between the axial thickness distributions on both sides of the product is smaller in conventional spinning due to the uniform feed ratio. In terms of forming limits, conventional spinning has a slightly better performance.