The Experimental Research Of The Saddle Workpiece By Multi-Point Sandwich Forming

Multi-point sandwich forming (MPSF) is a new flexible forming technology to manufacture three-dimensional sheet metal part with large size and multi-radius, which utilizes a pair of matrices of adjustable punches with the designed tool surface. As a flexible forming technology, it is especially suitable to form workpieces with small batch quantities, such as ship-plate, the petals for wind tunnel and large vessel.Multi-point sandwich forming combines the feature of the multi-point die forming and the polyurethane forming. In this process, one half of a conventional die set is substituted by a discrete die with wide spaced pins plus deformable die sheet and a polyurethane upper die is used as the other half. Using a polyurethane interpolator enables smooth workpiece surface to be obtained, even when the die sheet is dimpled by the pins of the reconfigurable die.In this paper, the program compiled by C is developed to transform surface coordinates from space to local coordinate system. Moreover, the program compiled by Basic is developed to seek the contact points between the pins and the die sheet. With the programs, the data of the model of multi-point sandwich die are provided.By multi-point sandwich forming, the experimental research of the saddle shape workpiece was carried out. The effects of the forming parameter were analyzed, such as the thickness of die sheet, the thickness of polyurethane interpolator, the arrangement of the elastic die and the forming force. And also the forming defects such as dimples and the wrinkling by finding out the reason they came out can be suppressed. The two-step forming process was used in the difficult forming range of the saddle workpiece. Furthermore, the forming limit of saddle shape workpiece with the experimental die was obtained.Finally, the tooling compensation of the saddle shape workpiece by multi-point sandwich forming is introduced simply. It is shown that the final workpiece shape is a result not only of springback, but also of the .polyurethane interpolator non-uniform deformation. The tooling compensation method can reduce shape error and improve the shape quality of products.