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Abstract: Multi-point stretch forming (MPSF) is a flexible manufacturing technique to form large sheet panels of mild curvature. The traditional fixed shape-stretching die is replaced by a matrix of punch elements, and the sheet metal are stretch-formed over the multi-point stretching die (MPSD) generated by the punch element matrix. In this paper, extensive numerical simulations of the processes for stretching parabolic cylinder, toroidal saddle and sphere parts were carried out by dynamic explicit finite element analysis. The forming results using multi-point die were compared with those of using traditional die. The use of an elastic cushion to suppress dimpling of the part caused by the discrete punch elements was investigated along with a discussion of its influence on part shape accuracy. The effect of the size of punch element and the shape of MPSD on the shape accuracy of formed parts were analyzed. The results may provide useful guidance on determining MPSF parameters and optimizing MPSF manufacture processes. [Copyright &y& Elsevier]

Abstract: A manufacturing process for fabricating a cylindrical crown gear drive that is provided with a controllable fourth order polynomial function of transmission error is proposed in this paper, and the procedures for creating the mathematical models of the tooth surfaces are described. In order to reduce the level of gear running noise, a pre-designed fourth order polynomial function of transmission error is assigned to the gear drive. To avoid edge contact, the tooth face of the output gear is longitudinally crowned by employing a form grinding wheel that is driven by a parabolic motion. Based on the theory of gearing, mathematical models of tooth contact analysis (TCA) are created, and mathematical models of principal curvatures and directions and contact ellipses are developed. A numerical simulation of meshing is performed, and the proposed gear drive is proved numerically to be able to reproduce the pre-designed fourth order polynomial function of transmission error. The influence of varying the parameter of parabolic motion of the grinding wheel on the dimensions of contact ellipses is also analyzed. [Copyright &y& Elsevier]