Experimentation and numerical simulation of the manufacture of an ellipsoidal workpiece by multi-point sandwich forming

To significantly reduce the time and cost of tooling development for sheet metal parts, a new reconfigurable die forming, the multi-point sandwich forming (MPSF) is being developed for parts with various curvatures, in small batch quantities. In this process, the die surface can be changed by adjusting the height of the pins in the lower die. Some elastic polyurethane pads are used as an upper die. To enable parts of good surface quality to be formed, an elastic interpolator and die sheet also are used in the process. The arrangement of each component of the tool set has a sandwich like structure, and therefore this process is called multi-point sandwich forming. To investigate this process, in the work described in this paper the die with ellipsoidal surface was chosen to manufacture workpieces in this paper. The effect of the thickness of interpolator on the height of workpiece dimples and forming errors along two typical sections of workpiece was investigated through experiment and the commercial FE simulation software ABAQUS was used to investigate the loading process and springback after unloading. Simulation enabled an explanation to be obtained as to why dimples occur in the middle edges of a workpiece. Also the final shape of the workpiece calculated by FE simulation was in good agreement with the experiment of result.