• Journal of the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.29-35
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• 2002

This study shows the process design and forming analysis of permalloy shielding can that support the automobile multi-display parts to indicate the accurate information of car. This study is particularly important, since the accuracy of permalloy shielding can is known to affect the magnetic properties such as coercivity and permeability quite sensitively. The objective functions are defects such as hemming wind, hemming length, hemming wrap and tightness in prehemming process. The pre-hemming angle is considered as design parameter. The commercial finite element program PAM-STAMP™ was used to simulate the pre-hemming and hemming process. The ANN (Artificial Neural Network) has been implemented for minimizing of objective function and for investigating effect of punch angle relevant to the pre-hemming process. The results of analysis to validate the proposed design method are presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.628-632
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• 2000

In the recent day, shielding can was made of permalloy materials for automobile display instrument. The good roundness has an effect on magnetic property such as the low coercivity and the high permeability. But the products having the roundness is transformed by the heat treatment, the sending to the company and the assembly process. So for the stiffness of the edge, it is necessary for hemming process to be added in the deep drawing process. And it has the good appearance to create a smooth edge rather than a razor edge with urr. In this paper, it is controlled to get the best hemming product by the Pre-hemming angle($105^{\circ}$, $120^{\circ}$, $135^{\circ}$). And Possible process and tool design modification, which may lead to quality improvement in hemming were tested experimentally and using FEM. The commercial finite element program PAM-STAMPTM was used to simulate the pre-hemming process and hemming process, and the predictions were compared with experimental results according to the pre-hemming angle.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.103-107
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• 2002

The 2nd forming process of flanging/hemming has recently many interest because it determines external quality of automobile. It is difficult to apply finite element simulation in flanging/hemming due to small element size which needs for expression of bending effect on the die corner and big model size of side door, back door, tank lid and like opening Parts. This paper shows the process of flanging/hemming simulation using finite element model for automotive panels. The explicit finite element program PAM-STAMP$\^$TM/ was used to simulate the flanging and hemming operations.

• Transactions of Materials Processing
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• v.16 no.3 s.93
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• pp.163-171
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• 2007

Due to the complicated character of the hemming process for automobile panels, it is very difficult to setup a consistent and reliable die design guide rule that require subtle decision of experienced experts and multiple trials during hemming die design and making. In this paper an automatic die design system of hemming units is pursued by presenting some algorithms, in which geometric data and constraints of the hemming units were converted to formula. The geometries and kinematics of all part for two kinds of hemming units, 2-link type and 4-link type were analysed kinematically to build the design algorithm. The algorithms were verified by automatic drawing used AutoCAD VBA program in example for the hemming unit design of a bonnet.

• Design & Manufacturing
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• v.10 no.1
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• pp.26-30
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• 2016

In this study, it was investigated by comparing the experimental hemming by the 3 steps and 2 steps in order to stabilize the quality of the hemming process. In the experimental results, the three-step hemming superior to the two-step one and the dimensional stability of part that was made by the three-step on was high. When the second stage Hemming has been found that the deflection caused by the force to the wear of the punch becomes larger plane can be folded by the hemming crimping and crimp uncertain.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.438-445
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• 2006

Due to the complicated character of the hemming process for automobile panels, it is very difficult to set up a consistent and reliable die design guide rule that does not require subtle decision of experienced experts during design stage and multiple trials during hemming die making. In this paper an automatic die design system of hemming units is pursued by presenting some algorithms, in which geometric data and constraints of the hemming units were converted to formula. two kinds of hemming units, 2-link type and 4-link type, were selected as examples and the geometries and kinematics of all parts were analyzed to build the design algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.2
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• pp.149-157
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• 2004

Implicit finite element analysis of the flat surface-straight edge hemming process is performed by using a commercial code ABAQUS/Standard. Methods of finite element modeling for springback simulation and contact pair definition are discussed. An optimal mesh system is chosen through the error analysis that is based on the smoothing of discontinuity in the state variables. This study has focused on the investigation of the influence of process parameters in flanging, pre-hemming and main hemming on final hem quality, which can be defined by turn-down, warp and roll-in. The parameters adopted in this parametric study are flange length, flange angle, flanging die corner radius, face angle and insertion angle of pre-hemming punch, and over-stroke of pre-hemming and main hemming punches.

• Transactions of Materials Processing
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• v.25 no.1
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• pp.29-35
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• 2016

In the current study, finite element analysis was conducted for the press hemming of automotive panels in order to predict various hemming defects such as roll-in and turn down. The analysis used the exact punch movement based on the cam location and considered the sealer between the inner and outer panels with an artificial contact thickness. The analysis results quantify the hemming defects especially at the flange edge in the matching region of the head lamp. A design of experiments along with the parameter study was used to obtain the optimum process parameters for minimizing hemming defects. The optimization process selects the intake angle, bending angle of the hemming punch, and the flange height of the outer panel. The optimum design process determines an appropriate tool angle and flange height to reduce the roll-in and turn-down as compared to the initial design.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.115-121
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• 2004

Hemming is the last farming process in stamping and determines external quality of automotive outer panels. Few numerical approaches using 3-dimensional finite element model have been applied to a hemming process due to small element size which is needed to express the bending behavior of the sheet around small die comer and comparatively big model size of automotive opening parts, such as side door, back door and trunk lid etc In this study, part model assembling method is suggested and applied to the 3-dimensional finite element simulation of flanging and hemming process far an automotive front hood.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.533-540
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• 2005

The hemming process, composed of flanging, pre-hemming and main hemming, is the last one of a series of forming processes conducted on the automotive panels, having greater influence on the outward appearance of cars rather than on their performance. The hem quality can be quantitatively defined by the hemming defects including turn-down/up, warp and roll-in/out. However, it is difficult to evaluate and predict the hem quality through an experimental measurement or a numerical calculation since the size of defects is very small. This study aims to precisely evaluate the hemming defects, especially turn-down and roll-in, through numerical and experimental approaches and to investigate the influence of process parameters on the hem quality, focused on how to simulate the same conditions as in the experiment by the finite element analysis (FEA). The FEA results on the turn-down and roll-in obtained from a model composed of the optimum-sized elements, including a spring element linked to the flanging pad, and given the double master contact condition between the inner and outer panels, had a good correlation with the experimental data. It is thought possible to make an early estimate of the hem quality in a practical automotive design by applying the methodology proposed in this study.