• Journal of the Korean Society for Precision Engineering
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• v.17 no.10
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• pp.77-82
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• 2000

The design of the prestressed cold extrusion die with two stress rings has been performed in this study. The cold extrusion has been simulated by the rigid-plastic FEM. The stress analysis of die has been performed for both after shrink fitting and during extrusion by using the elastic FEM and the Lame's equation. According to the variation of interferences and diameter ratios, the maximum effective stress has been evaluated. As results, interferences and diameters were determined by the minimization of the maximum effective stress of die insert. The comparison of the maximum effective stress between the proposed design and the conventional design has been discussed. It was found that the maximum effective stress in the die insert is considerably affected by the stiffness of the first stress ring.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.245-250
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• 1999

In order to design micro-fan appropriately, flow chacracteristics and mechanics should be carefully considered. The present work concerns with design procedure for a micro-fan using NACA(National Advisory Committee for Aeronautics) airfoil series. The generation of fan profiles is carried out automatically by defining related parameters, which is also converted to CAD/CAM data automatically. The optimal parting surface for the mold of micro-fan is also calculated by analyzing the geometric data numerically. As a consequence, the high capacity micro-fan can be developed successfully with a high-quality and an improved efficiency.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.1016-1023
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• 2000

The present work is concerned with three-dimensional finite element analysis of the hollow section extrusion process using a porthole die. The effects of related design parameters are discussed through the finite element simulation for extrusion of a triply-connected rectangular tubular section. For economic computation, mismatching refinement, an efficient domain decomposition method with different mesh density for each subdomain, is implemented. In order to obtain the uniform flow at the outlet, design parameters such as the hole size and the hole position are investigated and compared through the numerical analysis. Comparing the velocity distribution with that of the original design, it is concluded that the design modification enables more uniform flow characteristics. The analysis results are then successfully reflected on the industrial porthole die design.

• Transactions of Materials Processing
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• v.5 no.1
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• pp.47-54
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• 1996

An improved nonparametric tool description based on successive refined nonparametric patches is proposed and the related criterion for refinement is also discussed. In the proposed scheme any required order of tool surface conformity can be achieved by employing successive refinements according to the suggested criterion. By using the suggested adaptive tool refinement technique based on the nonparametric patch tool description the locally refined nonparametric tool surface with economic memory size and sufficient accuracy as well as with favorable characteristics for contact treatment can be obtained directly from the parametric patch related with commercial CAD system. Computation is carried out for a chosen complex sheet forming example of an actual autobody panel in order to verify the validity and the efficiency of the developed tool surface description.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.249-250
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• 2010

• Journal of the Korean Society for Precision Engineering
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• v.22 no.1
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• pp.167-174
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• 2005

The design for cold extrusion dies is very important, because the die insert is subjected to very high radial and hoop stresses. The design of cold extrusion dies has many constrained conditions. In this paper, the used assumptions are such that the yield strength of each ring is selected according to the allowable tensile or compressive hoop stress in each ring and the maximum allowable inner pressure, when yielding occurs in one ring of the dies, is obtained by the proposed equation. In order to obtain design variables, such as diameter ratios and interferences, using the maximum inner pressure, the flexible tolerance method was used for shrink-fitted thick-walled cylinders. ANSYS APDL was used to perform the repeated analysis of deformation of the dies due to the variation of the design variables. The response surface methodology is utilized to analyze the relationship between the design variables and the maximum radial displacement of the die insert during extrusion. From the results, it is found that outer diameter of the die insert has the largest effect on the minimization of maximum radial displacement at the inner surface of the dies.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.5
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• pp.91-97
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• 2020

A split-die design for the cold forging of symmetric parts such as those having a hexagonal cross-section is presented in this paper. Parts with a hexagonal cross-section, such as bolt heads and nuts, should be forged with a die that has a hexagonal-shaped hole. A split type die is required to mitigate the buildup of stress concentrations located at the corners of the hexagonal hole. Generally, the insert of a hexagonal die is made by cutting each corner of a cylinder using a hexagonal hole and then combined with the die and shrink-fitted. However, split dies face problems when extruding material at the corners of the hexagonal split die. To address this problem, two types of split dies were evaluated: rounded hexagonal dies and angular hexagonal dies. The effects of the pre-stress ring on the dies were compared and analyzed and results show that using the angular split hexagonal die can extend the lifetime of forging dies.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.7
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• pp.153-162
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• 2004

This paper describes a research work on the die design for the deep drawing ＆ ironing(D.D.I.) of high pressure gas cylinder. D.D.I die set is large-sized die used in horizontal press, which is usually composed of drawing, and ironing die. Design method of D.D.I. die set is very different from those of conventional cold forging die set.. Out diameter of the die set is fixed because of press specification and out diameter of the insert should be as small as possible for saving cost of material. In this study, D.D.I die set has been designed to consider those characteristics and the feasibility of the designed die has been verified by FE-analysis. In addition, the automated system of die design has been developed in AutoCAD R14 by formulating the applied methods to the regular rules.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.434-437
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• 2007

Cold forging technology of a gear product is being interested in the dimensional accuracy, high stiffness and reduction of stress concentration. Especially it is needed to avoid the damage due to extremely high local pressure. Therefore it is important to ensure high pressure in die design. In this study, single die insert type and splitted die insert type are considered to recognize the notch effects in the die of sprocket forming. The stress concentration has been released at the notch area by the cushion effect in the splitted die insert.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.569-574
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• 2002

As consumer's desire becomes various, agility of mold manufacturing is most important factor for competence of manufacturer. In common works to use commercial CAM system to generate tool path, some decision making process is required to produce optimal result of CAM systems, The paper proposes a methodology for computer-assisted tool selection procedures for various cutting type, such as rough, semi-rough and finish cuts. The system provides assist-tool-items for machining of design model part of injection meld die by analyzing sliced CAD model of die cavity and core. Also, the generating NC-code of the tool size is used to calculate machining time. The system is developed with commercial CAM using API. This module will be used for optimization of tool selection and planning process.