Influence of blank flatness on the forming characteristics in the spinning of aluminum alloy thin-walled special head

The initial blank employed to form aluminum alloy thin-walled special head was cut in metal strip, which has the unavoidable fluctuation of blank thickness, i.e., blank flatness (BF) because of the rolling technology. The BF increases the uncertainty of forming process and causes difference in the forming quality. In this paper, to research the influence of BF on forming quality, different BF types are defined as edge-down, edge-up, edge-w, and ideal blank flatness, and the different BF values are ± 0.5 mm and ± 1.0 mm got by experimental measurement. And three-dimensional finite element (FE) spinning models considering BF were established. Different BF types are achieved by assigning discrete ordinates to nodes using Latin hypercube sampling. Models are verified by theoretical methods. Further, influence of BF on spinning force (F), degree of inhomogeneous deformation (φ), and thickness of head (T) is investigated. The results show that the BF has different influence on F in the earlier, middle, and later stage of spinning. φ of BF of edge-down is largest; φ caused by BF = ± 0.5 mm is less than that caused by BF = ± 1.0 mm. BF type and value of the metal blank have no significant influence on T. In conclusion, the BF of the circular blank required by the spinning head should be typed in edge-w, and the value should be less than ± 1.0 mm. The research offers an in-depth understanding of the effects of BF on the forming quality in the head spinning process and thus lays a basis for choosing the initial blank.