Papers by Keyword: Multi-Point Forming

Abstract: Through the forming of large and thick sheet metal cylindrical parts, it was found that symmetrical abnormal arching defects appeared at both ends of the first and tail ends in the length direction. In response to this phenomenon, the finite element simulation verification and comparison of the two processes of multi-point mold forming and integral mold forming are carried out. The analysis results show that this kind of end effect exists in both the multi-point mold forming and the overall mold forming process, and the overall mold forming effect is better. The multi-point mold has a small springback in the length direction, which is versatile and compatible.

Abstract: Unlike multi-point die forming (MPDF), multi-point press forming (MPPF) takes full advantage of the flexibility of multi-point forming (MPF). In the process of MPPF, the punch elements always keep in contact with the sheet metal, developing instantaneous forming surfaces, which clamp and deform the plates. In this study, based on the spherical surfaces, the formability of both MPPF and MPDF were simulated through finite element software. The effects of the two methods on dimple, wrinkle and springback defect were comparatively analyzed. Also the shape error of MPPF was studied. We find MPPF can significantly inhibit dimple and wrinkle, thus obviously reducing the maximum strain and homogenizing the distributions of stress and strain of the parts. The largest vertical springback value decreases from 0.514mm to 0.257mm and the stress is released more completely after unloading. The edge effect reduces the curvature in the area far away from the center, greatly magnifying the shape error. The increase in the numbers of punch elements and in the dimensions of elastic cushions can significantly weaken the edge effect and improve the forming precision. These analyses show MPPF has better formability for metal sheets than MPDF.

Abstract: Multi-point forming process has been developed to shape the sheet metal with bidirectional curvature. However, the forming force usually climbs too high so that the dimension of the forming machine should be designed to meet it. To solve this problem, the multi-point incremental forming (MPIF) process was proposed in this paper. First, the principle of this new forming process was introduced. Then, the experimental device was designed. Next, the MPIF process was simulated by a finite element model. The forming effects including displacements, thickness, and curvatures were visualized and discussed in detail. It was found that there is no obvious thickness change during the forming process. The advantage of this forming process is that the shape of the sheet metals adaptable and controllable with small forming force.

Abstract: The finite element model of flexible clamp multi-point stretch forming (FCMPSF) was set up, and extensive contradistinctive analysis of forming limit and forming accuracy between FCMPSF and RCMPSF were done. The results show that under the same forming conditions, spherical part formed by FCMPSF is not easy to fracturing, dimpling and springback, and is easy to fit the die. The reason for this was analysed. The non-fracturing limited graph, the non-dimpling limited diagram and the average springback value of spherical parts formed by FCMPSF and RCMPSF were obtained. Finally, the forming experiment and error analysis of spherical part formed by FCMPSF were done, the results indicate that 3D parts with large transversal curvature can be shaped by FCMPSF and the forming quality was guaranteed.

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: Growing requirements of small-batch, high-quality and customized products are motivating the development of innovative flexible polymer processing techniques. The paper demonstrates the possibility of employing the multi-point forming (MPF) technology to produce low-cost, small-batch and customized polycarbonate (PC sheet components. Experiments have been performed by means of an experimental setup designed for processing polymer sheet and the overall investigation is focused on the characterization and evaluation of the effects of processing parameters on forming quality. The results show that the forming defects can be eliminated under appropriate processing parameters and that the shape of formed part is in good accordance with the desired shape.

Abstract: To effectively form three-dimensional sheet metal parts with various curvatures produced in small quantities, flexible rolling forming, a new flexible forming method is being developed. Firstly, concept of the flexible rolling forming is introduced and its characteristics and working principle are analyzed by the combination of conventional rolling and multi-point forming. Secondly, the equipment design scheme of flexible rolling forming is put forward and the relevant device is developed. Thirdly, the feasibility and practicality of flexible rolling forming are verified by rolling several typical three-dimensional surface parts such as spherical and saddle surface parts by self-developed device. Finally, verifies the reasonableness of the device and at the same time possesses the important guiding significance to the research and development of practical flexible rolling forming equipment.

Abstract: Although multi-point forming (MPF) is an advanced processing technique and has been investigated comprehensively as a metal working operation, there are few papers published to deal with MPF of polymers. The present paper reviews the features of MPF and evaluates the possibility of producing polymer components by means of MPF. The experimental research work makes use of PC sheets with a thickness of 3.82 mm. Numerical simulations were performed with the software ABAQUS, then spherical and saddle-shaped components were manufactured by MPF. The geometrical deviations between shaped components and their original CAD/CAM models were obtained to investigate the forming accuracy. The results confirm that MPF of PC sheet has potential for the manufacture of complex components.

Abstract: Multi-point holder forming (MPHF) adopts series of coupled holder punches, arranged between forming punches, to clamp the whole sheet in the forming zone. The multi-point holder forming processes of spherical parts of titanium mesh plate were simulated by finite element code, and the results were compared with those of multi-point die forming (MPDF). The influence of holder punch load on the deformation of spherical part in multi-point holder forming was investigated. The shape error analysis of titanium mesh formed by MPHF was performed in finial. The results showed that the spherical part had more excellent performance in multi-point holder forming, and the more deformation the titanium mesh was, the larger force of holder punch would be needed. In addition, there was a small shape error for titanium mesh part formed by MPHF before springback.

Abstract: In this paper, authors present a highly flexible tooling system based on reconfigurable multi-point thermoforming (MPTF) methodology, which has been developed within an EU-granted FP7 project. The MPTF technology employs an actuated-punch matrix to dynamically configure a controllable tool working surface through digitally adjusting relative displacement of each punch in the matrix. Novel MPTF methods have been proposed through re-changing configurations of actuated-punch tooling system according to rapid thermoforming principles and relevant cladding applications. The tooling system includes an industrial-scale prototype of an MPTF tooling integrated with functional CAD/CAE/CAT software interfaces. The numerical simulation with an explicit FEM predicts the unexpected deformation defects of dimples and wrinkles regarding to discrete contact boundaries between punches and the sheet blank. Innovative techniques of variable blank-holder and deformable cushion have been implemented to suppress wrinkling and eliminate dimpling effectively. The tooling system has been successfully applied to manufacture complex double-curved panels, which are described as application examples. Compared with conventional fixed moulds, the flexible tooling offers robust, rapid and re-changeable means to make mould-less manufacturing large freeform panels.