Research on the process of flexible blank holder in multi-point forming for spherical surface parts

The technology of flexible blank holder (FBH) in multi-point forming (MPF) is a novel forming process for spherical surface parts, which is proposed based on the flexible method. According to the mechanical characteristics of the forming parts as well as the stress and strain state, the forming parts with good quality are obtained by reasonable distribution of the blank holder block and different blank holder force (BHF) at different locations. An original rigid FBH device is designed. Finite element analysis models of flexible blank holder (FBH) and no blank holder (NBH) are established, spherical surface parts with different BHF are simulated and then acquired the optimal BHF. The results indicate that FBH forming technology can avoid wrinkling defects effectively, the stress and strain are smaller and distribute uniformly, sheet metal flow is more uniform, and thickness distribution is more reasonable. Finally, a series of experiments of 08Al and 1060 with different thickness are completed in MPF dies to confirm the feasibility and versatility of the FBH device.