Numerical Simulation And Forming Process Research On Multi-point Forming With Flexible Blank-drawer For Sheet Metal

Multi-point forming(MPF) is a new kind of flexible manufacturing technology for sheet metal, having been widely used in several manufacturing field so far, such as aerospace, ship plate, automotive covering parts, building exterior and so on. With the continuous development of sheet processing technology, higher requirement for the product personalization is needed, so the flexible blank-drawer multi-point forming technology is put forward in this article. It is to use the pressure of multi-point die for the metal sheet, which is clamped by discrete clamps all around, at the same time, the flexible clamps apply edge force to the plate, thus plastic deformation will occur on the sheet and then a complex curved surface parts is obtained. Compared with other stamping technology, it can not only process more complex curved surface parts with good quality, but also can achieve a rapid prototyping of sheet metal by adjusting the mold profile of upper and lower basic body.The research background, basic principle and experiment device of the flexible blank-drawer multi-point forming have been introduced detailly in this paper. Based on sphere and saddle shape part,corresponding finite element models of flexible blank drawer multi-point forming have been set up, and the numerical simulation analysis of different process parameters has been carried on as well. The primary research conclusions are as follows:1.Based on sphere and saddle shape part, corresponding finite element models of rigid blank-holder, flexible blank-holder and flexible blank-drawer multi-point forming have been set up, and the numerical simulation results of different process has been contrasted as well. The results show that as for the workpiece obtained from rigid blank-holder forming, stress concentration phenomenon appears in the straight wall area, cracking is easy to happen. The workpiece obtained from flexible blank-holder forming, the deformation trend of flexible blank-holder is consistent with the workpiece surface, but its stress and strain is uneven, thus wrinkling defects is easy to happen on the corners. The workpiece obtained from flexible blank-drawer forming, the arrangement of discrete clamp agrees with the sheet deformation, its stress and strain is more uniform, thus cracking and wrinkling are not easy to happen, the best effect is obtained.2.The influences of clamp number, edge force, material and friction coefficient on flexible blank-drawer forming have been explored. The results indicate that the more clamp, the stress and strain of forming area is more uniform, the forming quality is better. Besides that, wrinkling defects can be effectively suppressed by edge force, but the lager is easy to produce cracking, so a reasonable edge force must be chosen. Moreover, the larger the yield strength of metal material is, the forming quality is better. The smaller the friction coefficient is, the contact resistance between metal sheet and elastic cushion is smaller, and the internal metal flow more smoothly.3.The influence of thickness of the elastic cushion on flexible blank-drawer forming have been studied also, the results show that the greater the elastic cushion thickness is, the contact stress is smaller, and the distribution of sheet metal parts is more uniform, the impression defect is suppressed, but its shape precision will be decreased.