• 폴리머
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• 제27권2호
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• pp.152-158
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• 2003

상업적으로 폴리(메틸 메타크릴레이트) (PU) 인조석을 생산하기 위한 두 가지 성형 방법으로 셀 성형법과 벨트 성형법이 있다. 그렇지만 셀 성형법은 생산성 면에서, 벨트 성형법은 설비비 및 생산단가 면에서 각각 단점을 갖고 있다. 그러므로 본 연구에서는 플라스틱 필름을 주형으로 이용하여 PMMA 인조석을 생산하는 새로운 성형 가공 방법에 대한 연구를 통해 벨트 성형법 및 셀 성형법의 단점을 극복하고자 하였다. PMMA 인조석의 생산을 위한 주형용 플라스틱 필름으로는 폴리(비닐 아세테이트) 필름을 사용하였다. 우수한 필름 성형 가공성을 나타낼 뿐만 아니라 경화 후 우수한 기계적 특성을 나타낼 수 있는 메틸 메타크릴레이트 배합물을 제조하고 이를 사용하여 필름 성형법에 의해 PMMA 인조석을 제조하였다. 필름 성형법에 의해 제조된 PMMA 인조석의 성능은 셀 성형법과 벨트 성형법에 의해 각각 제조된 상업용 PMMA 인조석의 성능에 비해 동등 이상의 우수한 성능을 나타내었다. 그러므로 본 연구에서 개발된 필름 성형법은 PMMA 인조석의 생산을 위해 상업적으로도 적용 가능성이 큰 것으로 사료된다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.105-108
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• 2006

The fuel cell is one of the promising environment-friendly energy sources for the next generation. The fuel cell provides good energy efficiency above 40% without pollution or noise. Different fuel cell types are usually distinguished by the kind of electrolyte. Among these, the proton exchange membrane fuel cell (PEMFC) has advantages of high power density. low operating temperature, relatively quick start-up, and rapid response to varying loads. The bipolar plate is a major component of the PEM fuel cell stack, and it takes a large portion of stack volume, weight and cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding and by machining. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. Flow channels were fabricated by compression molding with design of experiments (DOE) to evaluate moldability. The cost for compression molding of graphite-composite bipolar plate was compared with machining cost to make the same bipolar plate.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.491-495
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• 2004

The industries use polymer materials for many purposes for they have many merits. The costs of these materials take up too great a proportion of the overall cost of products that use these materials as their major material. It is advantage for polymer industries to reduce these costs. The microcellular foaming process was developed in the early 1980s to solve this problem and proved to be quite successful. Microcellular foaming process uses inert gases such as $CO_2$, $N_2$. As these gases solve into polymer matrices, many properties are changed. The microcellular foaming process makes the glass transition temperature of polymers to low, and diminish the residual stress of polymer matrices. Besides, the microcellular foaming process has several merits, impact strength elevation, thermal insulation, noise insulation, and raw material saving etc. This characteristic of microcellular foaming process has influenced by cell morphology. The cell morphology means cell size and cell density. The cell morphology has influenced by many factors. The examples of factor are pressure drop rate, foaming temperature, foaming time, saturation pressure, saturation time etc. Among their factors, pressure drop rate is the most important factor for cell morphology in microcellular foaming injection molding process. This paper describes about the cell morphology change in accordance with the pressure drop rate of microcellular foaming injection molding process.

• Design & Manufacturing
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• 제13권3호
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• pp.29-34
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• 2019

Cell phone injection is characterized by its small size and thinness. In addition, the product has a short cycle time, requiring a very short production schedule. To produce more accurate products faster, data from experience in producing similar products is required. In this study, two mobile phone models are presented. In this study, the quality problems caused by molding analysis and actual injection molding were analyzed and made into a database. As a result, it was considered that all the defects in the molding analysis do not affect the product in some cases, rather than appear as defects in the actual product. All defects shown in the molding analysis can be made into a database, and based on this data, it will be possible to obtain an effect that can predict more accurately whether it will cause problems after injection.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.422-425
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• 2008

Recently, electronic products and related parts are required to have thin thickness because of small form factor. To go with the trend, LGP(light guide plate) of LCD BLU(Liquid Crystal Display Back light unit: It is one of kernel parts of LCD) for cell phone has the thickness of 0.3 mm and the battery case of cell phone has 0.25 mm. Accordingly, high speed injection molding is required to make products which have thin thickness. High speed injection molding means that the resin is injected into the cavity at higher than normal speed avoiding short shot. In the case of hydro-mechanical high speed injection machine, it requires the design for hydraulic unit to make high injection speed and the design for control unit to control hydraulic unit. In the present paper, we concentrated on the molding stability of hydro-mechanical high speed injection machine to make an LGP of 0.3 mm thickness.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.253-259
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• 2002

Micro cell structures with high aspect ratio were fabricated by injection molding method. The mold inserts had dimension $1.9cm\times8.3cm$ composed of a lot of micro posts and were fabricated by LIGA process. The size of the micro posts was $157{\mu}m\times157{\mu}m\times500{\mu}m$ and the gaps between two adjacent posts were $50{\mu}m$. Using Polymethylmethacrylate (PMMA) injection molding was performed. The key experimental variables were temperature, pressure, and time. By controlling these, good shaped mim cell structures with $50{\mu}m$ in wall thickness and $500{\mu}m$ in depth were obtained. In order to understand micro molding mechanism, shape changes of molded PMMA were studied with experimental variables. And the durability of mold insert was investigated, too. The results show that the most important factor in molding processes was the mold temperature that is closely related to the filling of the melt into the micro cavity. And the holding time before cooling showed a great effect on the quality of molded PMMA.

• 소성∙가공
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• 제17권8호
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• pp.657-661
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• 2008

Recently, products of electronic industry and related parts are required to have the thickness thinner and thinner to reduce the part weight. To go with this trend, LGP(light guide plate) of LCD-BLU(Liquid Crystal Display-Back Light Unit: It is one of kernel parts of LCD) for cell phone has the thickness of ${\sim}0.3mm$ and the battery case of cell phone has ${\sim}0.25mm$. Accordingly, high speed injection molding is required to mold products which have thinner parts. To achieve high speed injection and proper control of hydraulic unit, various design was applied to conventional injection unit. In the present paper, we concentrated on the molding stability of hydro-mechanical high speed injection machine to make an LGP of 0.3mm thickness.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.97-98
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• 2012

• Design & Manufacturing
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• 제13권2호
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• pp.30-36
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• 2019

Traditional cell culture(2-dimensional) is the method that provide a nutrient and environment on a flat surface to cultivate cells into a single layer. Since the cell characteristics of 2D culture method is different from the characteristics of the cells cultured in the body, attempts to cultivate the cells in an environment similar to the body environment are actively proceeding in the industry, academy, and research institutes. In this study, we will develop a technology to fabricate micro-structures capable of culturing cells on surfaces with various curvatures, surface shapes, and characteristics. In order to fabricate the hemispheric plastic structure(thickness $50{\mu}m$), plastic preform mold (hereinafter as "preform mold") corresponding to the hemisphere was first prepared by injection molding in order to fabricate a two - layer structure to be combined with a flat plastic film. Then, thermoplastic polymer dissolved in an organic solvent was solidified on a preform mold. As a preliminary study, we proposed injection molding conditions that can minimize X/Y/Z axis deflection value. The effects of the following conditions on the preform mold were analyzed through injection molding CAE, [(1) coolant inlet temperature, (2) injection time, (3) packing pressure, (4) volume-pressure (V/P). As a result, the injection molding process conditions (cooling water inlet temperature, injection time, holding pressure condition (V / P conversion point and holding pressure size)) which can minimize the deformation amount of the preform mold were derived through CAE without applying the experimental design method. Also, the derived injection molding process conditions were applied during actual injection molding and the degree of deformation of the formed preform mold was compared with the analysis results. It is expected that plastic film having various shapes in addition to hemispherical shape using the preform mold produced through this study will be useful for the molding preform molding technology and cast molding technology.

• Journal of Information Display
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• 제10권2호
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• pp.68-71
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• 2009

A replica-molding method of fabricating a dual-gap substrate for transflective liquid crystal (LC) displays is demonstrated. The dual-gap substrate provides homeotropic alignment for the LC molecules without any surface treatment and embedded bilevel microstructure on one of the two surfaces to maintain different cell gaps between the transmissive and reflective subpixels. The proposed transflective LC cell shows no electro-optic disparity between two subpixels and reduces the panel thickness and weight by 30% compared to the conventional transflective LC cell, which has two glass substrates.