• Transactions of Materials Processing
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• v.16 no.6
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• pp.457-462
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• 2007

The drawbeads, which are used for controlling the flow of the sheet into die cavity by imposing the tension and for preventing the forming defects like wrinkling, springback, etc. during the sheet forming process, affect the formability strongly because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces is manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. The drawbead forces obtained from the experiment were compared with those calculated in the numerical simulation of stamping process of automotive fender. Good agreement was found so that the experimental measurements can be used in the simulation of auto-body stamping process.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.126-132
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• 2005

In this paper, an auto-design system is introduced for a stamping tool based on commercial computer aided design system with its drafting language. The auto-design system consists of tool oriented product design subsystem which modifies and configures the product drawing, tool concept design subsystem which make a design of the punches and their punching progression and parts design subsystem that makes automatic dimension. The system is applied to the mechanical design of the stamping tool. The main logic of the system is based on half-edge theory, a kernel for the 3 dimensional CAD system, which is applied to 2 dimensional drafting auto-design system. The auto-design system enables to conspicuously reducing the designing time of the tool. In addition, there is little drafting error that had been about 3% without auto design program. It is effective to reduce the development time for new products because of rapid designing time of the tools, standardization of the stamping tool and the drafting rule for the auto-design system. The auto-design system yields high efficiency of the tool manufacturing system.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.86-91
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• 2005

The stack, the core unit of the MCFC system, is composed of the three main parts which are the electrodes, the matrix keeping the electrolyte and the separator. Among these, the separator made of low carbon steel is manufactured by some sheet metal forming processes. The flatness of flange of the mask plate of the separator is crucial not only to enhance the stack performance but also to reduce the production cost. This study has focused on the enhancement of flatness of the mask plate flange by controlling some process parameters like the punch and die comer radii, the blank holding force, the friction coefficient and so on. The springback phenomenon occurring in the flange drawing process has been studied first using the finite element method (FEM) in order to understand what causes the springback. The distribution pattern of local longitudinal stress in the flanged part has been revealed very important in predicting the final shape of the flange. This fact has been backed up by the experimental results carried out with the developed test dies.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.174-182
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• 1999

This paper describes a research work of developing a computer-aided design of product with bending constraints and piercing for progressive working. an approach to the CAD system is based on the knowledge-based rules. Knowledge for the CAD system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written AutoLISP on the AutoCAD with a personal computer and is composed of four main modules, which are input and shape treatment, flat pattern layout, production feasibility check, and strip-layout module. Based on knowledge-based rules, the system is designed by considering several factors, such as radius and angle of bend, material and thickness of product, complexities of blank geometry and punch profile, bending sequence, availability of press. Strip layout drawing generated by piercing with punch profiles divide into automatically for external area is shown into graphic forms, including bending sequences for the product with piercing and bending constraints. Results obtained using the modules enable the designer and manufacturer of piercing and bending dies to be more efficient in this field.

• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.91-96
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• 2017

In this computational study of optical fiber manufacturing, WOW (wet-on-wet) double coating process on freshly drawn glass fiber has been numerical modelled and simulated using a simplified geometry of typical optical fiber coating apparatus. The numerical domain includes primary and secondary coating dies along with secondary coating cup and the interface between primary and secondary coating liquids are investigated using level set method. Coating liquid viscosity is an important parameter and its dependence on temperature is also considered. Since there would be possibility for pressure and temperature of primary coating liquid to be increased substantially at high fiber drawing speed, the effects of increased pressure and temperature of primary coating liquid are examined on flow patterns of coating liquids in secondary coating cup. In case that both pressure and temperature of primary coating liquid are high enough, liquid interface becomes noticeably unstable and this flow instability could adversely affect the uniform coatings and final quality of produced optical fiber.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.80-85
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• 2018

The present investigation on optical fiber mass manufacturing features the computational modeling and simulation on a double layer liquid coating process on glass fiber surface. The computational model employs a simplified geometry of typical fiber coating system which consists of primary and secondary coating dies along with secondary coating cup. The viscous dissipation in coating flow is incorporated into the double layer coating process simulations. Heavy temperature dependence of coating liquid viscosity is also considered in the model. The computational results found that the effects of viscous dissipation on both primary and secondary coating layer thicknesses are highly significant at higher drawing speed. Several important coating process parameters such as supply temperature and pressure of primary and secondary coating liquids are investigated and discussed in order to appreciate how those parameters affect the double layer coating layer thickness on fast moving glass fiber.