Optimisation of multi-point forming process parameters

Abstract

The need for sheet metal forming using reconfigurable dies has increased due to rapid changes in part design to meet customer requirements, especially in the automotive industry. Reconfigurable dies have relatively low manufacturing cost compared with solid dies, and the same tool can be readily changed to produce different parts. Previous investigations have focused on avoiding defects without taking into account the effects of process on the quality characteristics of fabricated parts. This study investigated the influence of parameters, such as the elastic cushion thickness, coefficient of friction, pin size and radius of curvature, on the quality of parts formed in a flexible multi-point stamping die. The aim was to determine the optimum values of those parameters. Finite element modelling was employed to simulate the multi-point forming of hemispherical parts. Using the response surface method, the effects of process parameters on wrinkling, deviation from the target shape and thickness variation were investigated and the process parameters yielding the best product quality characteristics were obtained. The results show that pin size and radius of curvature have the greatest influence on wrinkling and deviation between formed and target shapes, while coefficient of friction, pin size and radius of curvature significantly affect thickness variation.

Multipoint forming using mesh-type elastic cushion: modelling and experimentation

“…The tensile test results are shown in Fig In addition to the experimental data, a power law equation was also applied to represent the stress of the sheet material (see Eq. 1) [2].…”

“…The mechanical properties of the DC05 sheet material are shown in Table 1. A mesh-type elastic cushion was prepared using polyurethane A-90 as it is one of the durable materials used in the MPF process [2]. Table 2 shows the solid and mesh-type elastic cushions used in the experiments.…”

“…Kareem and Imad [3] studied the influence of localised deformation on the quality of the deformed sheet and the importance of using the elastic cushion in reducing the formation of dimples, but they also found that using a very thick elastic cushion degrades the accuracy of the fabricated part. On the other hand, Essa et al [2,8,20] studied the effect of elastic material, friction coefficient and thickness on the surface quality. They were able to optimise the elastic material type and thickness for better product quality parts.…”

Effect of pin arrangement on formed shape with sparse multi-point flexible tool for creep age forming

“…For AA6082-T6 used in the study, = 290 MPa, K = 151.1 MPa and N = 0.684 at room temperature, which were obtained by fitting Eq. (14) to room temperature tensile test data of AA6082, as shown in Fig. 6.…”

“…[12,13]. The effect of thickness [14], hardness [15] and materials [16] of elastic cushions on formed quality of test blanks with MPF tool has been investigated and the results indicated that a higher forming shape accuracy can be achieved by elastic cushions with smaller thickness and greater hardness. However, the thickness of elastic cushions should be above a critical value to avoid apparent dimples in formed blanks [17].…”