Papers by Keyword: Elastic Cushion

Abstract: Multi-point Sheet metal forming is a flexible technique in which a discrete punches are used to generate the continuous 3-D surface . The proposed die comprises a set of matrices of a closely stacked discrete punches arranged to form a cavity in which a free form surface can be formed .The working surface of the multi-point die are modeled by a uniform B-spline and constructed by adjusting the height of each punch manually. Finite element simulation for the process was performed to study the effect of punch number on the shape error and thickness variation. Experimental work include the building of multi-point die to form the aluminum sheets. The effect using rubber interpolators on dimpling defect were also studied . The results revealed that thickness variation error between the numerical and experimental results is equal to 5% .

Abstract: Springback is a problem that must be solved in multi-point forming in this paper, finite element software ls-dyna was used to simulate plate stamping springback. 3mm thick elastic cushion inhibited dimple of sheet forming, but the use of elastic cushion and plate springback would lead to shape error. A method was proposed which modified the forming surface of element group in the Multi-point forming (MPF) by iterative ways according to the numerical simulation results. The accuracy of forming was improved after two compensation, it was proved that this method can compensate springback of the multi-point forming.

Abstract: Multi-point forming (MPF) is an advanced flexible manufacturing technology for three-dimensional sheet metal forming. The substance of MPF is replacing the conventional solid dies by a set of discrete punches called ‘‘punch group’’. Because the reconfigurable discrete punches are used, part manufacturing costs are reduced and manufacturing time is shortened. However due to the discrete contacts between the workpiece and punches, the dimple defects occurred, which are inevitable and particular for MPF. For thick plate, the surface defect is the mainly dimple defect during its MPF process. In this study, elastic cushion was proposed to prevent these surface defects. The dynamic explicit finite element method was chosen to implement the simulation of MPF process. The Hill’s anisotropic yield criterion was used to describe the workpiece material behavior, and the elastic cushion was described with using the hyperelastic material model. The method to determine each punch position to construct forming surface was introduced. The MPF process with and without using elastic cushion was simulated to study the effect of the elastic cushion on preventing the surface defects. The relevant experiment was implemented, and it verified that the elastic cushion is effective method to suppress the surface defects during the thick plate MPF process. Keyword: flexible forming process (FFP), elastic cushion, surface defects, multi-point forming (MPF), thick plate, numerical simulation

Abstract: In this paper, the basic theory of multi-point stretching process was introduced, the process of multi-point stretching of saddle part was simulated, the generation and suppression of dimples were studied [1~3]. The results showed that dimple is specific defect in the multi-point stretching process; the dimples can be suppressed effectively by elastic cushion technology. Thicker elastic cushion is more effective to suppress dimples, but the error between formed workpiece and objective shape will get large. By adopting elastic cushion with appropriate thickness, workpiece with smooth surface can be obtained and the forming error is small.