• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.281-286
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• 1993

Projection TV에는 시각 품질을 최종적으로 표시하는 디스플레이 소자인 비구면플라스틱 렌즈를 적용하고 있으나 전량 일본에서 완제품으로 공급 받고 있다. 플라스틱 비구면 렌즈를 성형하기 위해서는 사출 공정에 대한 철저한 이해 와 폴리머의 광탄성 거동에 대한 개념이 핵심이라고 말할 수 있다. 복굴절성 실험은 폴리머의 유변학적 거동을 파악 하는데있어 가장 유용한 실험중의 하나이다. 본 글에서는 이와 관련된 사항인 복굴절성, 잔류 응력 형성 메카니즘, 밀도이완 작용의 상관관계와 비구면 렌즈의 성형 조건 및 공정에대해 기술 하였고, 또한 측정된 수지데이타를 이용 상용 S/W를 사용하여 유동, 냉각, 보압 ( 압축) 및 수축 해석을 실시 하여 각 stage에서 경험한 온도 와 압력의 이력에따라 변화하는 열 응력에 기인한 잔류 응력 계산 Pg을 개발 상용 S/W 와 비교 검증 하였다.

• 기계와재료
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• v.23 no.3
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• pp.82-95
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• 2011

다결정압연판재는 열가공공정을 거쳐서 생산되므로 공정의 특성을 반영하는 미세조직/집합조직 특성을 가지게 된다. 결정립들은 특정방향으로 배향하고 결정립의 형상과 크기도 변화한다. 이러한 변화는 거시적으로 다결정판재의 이방성으로 귀결이 되는데, 근본적으로 판재를 구성하는 단결정들의 기계적 물성이 각각의 방향별로 이방성을 띄기 때문이다. 본 자료에서는 압연공정시 다결정판재의 수직/평면이방성의 발생원인을 집합조직과 결정소성학을 이용하여 제시하고자 하였다.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2221-2223
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• 2000

본 연구에서는 새로운 개념의 초정밀 가공기술인 LIGA 기술(이하 X-선 가공기술이라 함)을 이용하여 정밀 격벽(barrier ribs) 성형용 Ni 금형을 제작하였다. 먼저 X-ray 투과도가 우수하며 내구성 및 기계적 강도가 뛰어난 새로운 재질의 graphite X-선 마스크를 제작하였으며 한정된 단위면적의 X-선 마스크를 이용하여 X-선 노광 면적을 최대화 할 수 있는 새로운 X-선 exposure 기술을 개발하였다. 제작된 barrier ribs 성형용 초정밀 금형의 전체 size는 170mm X 130mm이며 pitch 간격은 110/55${\mu}m$ $\pm$ 0.7${\mu}m$ 이다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4057-4064
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• 2014

In this paper, attempts were made to design a preform for a final punch inexpensively using the proposed approximate optimization method or metamodel-based simulation optimization. The design objective of this work is to achieve a uniform distribution of effective strains, the angle dimension of the preformed punch is chosen as a design variable, and maximum underfill ratio is used as a constraint. For this optimization, a computer simulation of a practical punch forging process is run using DEFORM software, in which a preformed punch(workpiece), a master punch(upper die), and a bottom die are dealt with. A validation method is introduced to determine if the simulation results match the actual forging process. In addition, this work presents the detailed design optimization procedure consisting of (i) generation of an initial metamodel, (ii) metamodel optimization, (iii) validation of metamodel-predicted optimum, and (iv) metamodel improvement.

• Design & Manufacturing
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• v.17 no.4
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• pp.72-78
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• 2023

Injection molding is a process widely used in various industries because of its high production speed and ease of mass production during the plastic manufacturing process, and the product is molded by injecting molten plastic into the mold at high speed and pressure. Since process conditions such as resin and mold temperature mutually affect the process and the quality of the molded product, it is difficult to accurately predict quality through mathematical or statistical methods. Recently, studies to predict the quality of injection molded products by applying artificial neural networks, which are known to be very useful for analyzing nonlinear types of problems, are actively underway. In this study, structural optimization of neural networks was conducted by applying multi-task learning techniques according to the characteristics of the input and output parameters of the artificial neural network. A structure reflecting the characteristics of each process step was applied to the input parameters, and a structure reflecting the quality characteristics of the injection molded part was applied to the output parameters using multi-tasking learning. Building an artificial neural network to predict the three qualities (mass, diameter, height) of injection-molded product under six process conditions (melt temperature, mold temperature, injection speed, packing pressure, pacing time, cooling time) and comparing its performance with the existing neural network, we observed enhancements in prediction accuracy for mass, diameter, and height by approximately 69.38%, 24.87%, and 39.87%, respectively.

• Elastomers and Composites
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• v.43 no.3
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• pp.173-182
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• 2008

Rubber-pad forming process for materials such as metal in which portions of the die which act upon the material is composed of a natural or synthetic rubber or elastomer material. This makes the rubber pad forming process relatively cheap and flexible, high accuracy for small product series in particular. In this study, we carried out the physical test and finite element analysis of elastomer such as natural rubber and urethane for steel rack rube forming. The non-linear property of elastomer which are described as strain energy function are important parameter to design and evaluate of elastomer component. These are determined by material tests which are uni-axial tension and bi-axial tension. This study is concerned with simulation and investigation of the significant parameters associated with this process.

• Composites Research
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• v.20 no.2
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• pp.10-16
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• 2007

The 2-step manufacturing method consisting of preforming and stamping processes was developed to manufacture composite bipolar plates for PEMFCS. The preform was composed of expanded graphite, graphite flake and phenol resin. Procuring conditions were optimized by checking the electrical conductivity, flexural strength and microstructure. Procuring temperature $(100^{\circ}C)$ slightly above the melting point of phenol powders $(90^{\circ}C)$ induced moderate curing, but also prevented excessive curing. Preforms utilizing the tangled structure of expanded graphite were easily fabricated at low pressure of 0.07-0.28MPa. The proper procuring time, 5min, was determined to fabricate the preform stably because insufficient and excessive procuring deteriorated the flexural strength of composite bipolar plates.

• Proceedings of the KAIS Fall Conference
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• 2010.11b
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• pp.937-940
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• 2010

본 연구는 fine blanking 프레스로부터 기능면으로 사용되는 100% clean cut 전단면을 얻는 fine blanking 공정에서 die roll을 최소화하기 위한 목적으로 성형 해석 및 실험적 방법을 통해 die chamfer 형상에 따라 성형되는 제품의 die roll size 변화를 검토한 것이다. fine blanking 과정을 묘사하기 위하여 deform 2D를 이용하여 성형 해석을 수행하여 die roll size를 예측하였으며, 실제 die chamfer가 다른 die insert를 제작하여 fine blanking 실험을 실시하여 die chamfer 형상에 따른 die roll size에 대한 해석 data와 실험 data를 비교 분석하여 die roll 길이 방향 size의 경향을 파악할 수 있었다. 이 연구 결과는 fine blanking 판재 성형에서 die roll을 최소화하기 위한 die chamfer 설계에 유용하게 적용될 것으로 판단된다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1061-1064
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• 1997

Micro injection molding technology is very important fiw mass product of micro structures or micro parts. And, it is so difficult that the molding technology of micro pole or thin wall(barrier rib) structures with high aspect ratio. In this stud). \vc intend to research on the basic technology of micro wall structure part:< with high aspect ratio by the inject~on moldins method. The mold for esperimenrs with micro multi-square structures was made by L, I(;A process. One square polc's size is 157 157pm. height 50011111. And the distance of each poles is 5011n1. 7'hus. molding products will be for~nctl like as the net structure with thin wall of about 50pn thickness.(aspect ratio 10) Ihrough the e~lxriment. \be obtained the prociuctr of micro multi-square slructure with bout 37.000 cell per a piece. 'Ihe micro injection molding process technolog for thin wall by multi-square structure mold was analy~cd.

• Proceedings of the KAIS Fall Conference
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• 2001.11a
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• pp.139-143
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• 2001

In injection molded parts, the ribs require more complicated mold cavities and cores. But it is necessary for the parts to attach the ribs for assembly, moldability and other functional purposes. To design them appropriately considering structural strength and injection molding, the profound knowledge that includes moldability, causal effects on the properties of the part is needed. This paper describes the design methodology which enables easy, simple, time and cost-effective design for the features.