• 한국생산제조학회지
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• 제18권4호
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• pp.417-422
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• 2009

The injection mold cooling circuit optimization was studied with a response surface method in the previous research. It took so much time to find an optimum solution for a large product due to an extensive amount of calculation time for the CAE analysis. In order to use the optimization technique in the actual design process, the calculation time should be much reduced. In this study, we tried to reduce the number of design variables with the concept of the close relationship between the depth and the distance of cooling channel. The optimum ratio of the distance to the depth of cooling channels for a 2-dimensional problem was 2.0 so that the optimum ratio was again sought out for 4 large automotive parts. Therefore, the number of design variables for the cooling circuit optimization can be reduced in half, resulting in much faster running time for the optimization as a design tool.

• Design & Manufacturing
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• 제6권2호
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• pp.84-89
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• 2012

In recent years, technology of press plastic working having made remarkable progress. We can say this because it facilitates mass production and have superior performances in machining speed and equivalency of quality than other processing methods. In characteristics of press plastic working, mold manufacturing according to characteristics of each product should be preceded before processing and it has a great influence on machining speed and quality of products and etc according to manufacturing method. Therefore, mold design technology is a critical technology in press plastic working. There are lots of variables in press plastic working according to worked material, mold materials, conditions of heat treatment, clearance and so on. Abrasion of mold depends on these kind of conditions and sheared surface which is crucial for quality of product also depends on them. In this study, we conduct research on abrasion loss of mold according to 8, 10 and 12% of clearance for thickness of 1.0mm of worked material out of mold design variables of the products whose worked materials are high carbon steel and carbon tool steel by a practical experiment.

• Design & Manufacturing
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• 제6권2호
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• pp.90-95
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• 2012

The sheet metal forming proceccing is very important and indispensable in the automotive industry because the accuracy of prsee worked parts is directly related to the automotive quality. But when making mold it is difficult and expensive to modify mold. mold design technology is a critical technology in press plastic working. When design the mold there are lots of variables in press plastic working according to worked material, mold materials, conditions of heat treatment, clearance and so on. Abrasion of mold depends on these kind of conditions and sheared surface which is crucial for quality of product also depends on them. In this study, we conduct research on abrasion loss of mold according to 8, 10 and 12% of clearance for thickness of 1.0mm of worked material out of mold design variables of the products whose worked materials are high carbon steel and carbon tool steel by a practical experiment and perform a comparative evaluation of difference of abrasion loss mold with the alloy tool steel (STD11) and Tungsten Carbide (WC).

• 한국정밀공학회지
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• 제34권2호
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• pp.89-94
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• 2017

Micro-screws can be defined by their outer diameter of generally less than 1 mm. They are manufactured by head forging and thread rolling processes. In this study, the thread rolling process was numerically analyzed for a micro-screw with a diameter and pitch of 0.8 and 0.2 mm, respectively. Through finite element (FE) analysis, the effects of two design parameters (die gap and chamfer height) on the dimensional accuracy were investigated. Three combinations of chamfer heights were chosen first and the corresponding die gap candidates selected by geometric calculation. FE analyses were performed for each combination and their results indicated that the concave chamfer height should be less than 0.3 mm, while a 10 ?m difference in the die gap might cause degeneration in dimensional accuracy. These results conclude that ultra-high accuracy is required in die fabrication and assemblies to ensure dimensional accuracy in micro-screw manufacturing.

• Elastomers and Composites
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• 제38권4호
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• pp.295-302
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• 2003

사출성형에서 성형품의 수축현상은 사출온도, 사출압력, 금형온도와 같은 성형공정에 따라 다르게 나타나며 게이트의 크기 등과 같은 금형설계에 따라서도 다르게 나타난다. 또한 수지의 결정화 유무에 따라 다르게 나타나고 있다. 본 연구에서는 여러가지 공정변수와 수지 특성에 따른 성형 수축률을 결정성수지인 poly(butylene terephthalate) (PBT)와 비결정성 수지인 polycarbonate (PC), poly(methyl methacrylate) (PMMA)를 사용하여 연구하였다. 결정성 수지가 비결정성 수지에 비해 약 3배 정도의 큰 수축률을 보였다. 사출 성형품의 성형 수축은 사출온도와 금형온도가 높을수록 그리고 사출압력이 작을수록 수축률은 커지는 경향을 보였다. 게이트의 크기가 커질수록 캐비티내의 압력전달이 원활하여 성형수축률은 작아 졌다. 또한 수지의 흐름방향과 흐름직각방향의 수축률 실험에서는 흐름방향의 수축이 더 작은 경향을 보였다. 게이트와의 거리에 따른 성형수축률은 게이트에서 가까운쪽의 수축이 먼쪽보다 더 큰 수축을 보였는데 이 현상은 잔류응력의 차이로 인하여 나타난 현상으로 해석된다.

• 대한기계학회논문집A
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• 제35권9호
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• pp.1027-1033
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• 2011

VCM 강판은 용융아연도금강판 위에 PET/PVC 코팅하여 가전제품의 외판 소재로 사용되고 있다. 본 연구에서는 VCM 강판의 프레스 성형 중 발생하는 PET 코팅층의 찢김을 저감하기 위해 프레스 성형공정변수를 재설계하였다. 프레스 공정변수들이 PET 코팅층의 찢김에 미치는 영향을 분석하기 위해 유한요소해석을 수행하였다. PET 코팅의 찢김 현상은 드로잉 성형시 제품의 코너부 소재두께의 증가로 인해 금형과 소재 사이의 과도한 마찰에 의해 발생한다. 이를 해결하기 위해 블랭크 형상의 변경을 통해 드로잉성형시 코너부의 소재두께 증가를 저감하였으며, 트리밍 공정시 플랜지부의 과도한 두께 증가부분을 제거하여 플랜지 성형시 소재두께가 금형간극 이하로 분포하도록 하였다. 또한 성형실험과 유한요소해석을 통해 재설계된 공정변수들을 검증하였다. 이를 통해 PET 코팅의 찢김이 없는 양호한 최종제품의 성형이 가능함을 확인하였다.

• Elastomers and Composites
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• 제48권4호
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• pp.300-305
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• 2013

사출성형에서 성형수축은 피할 수 없는 현상이다. 따라서 성형수축을 줄이기 위한 연구가 필요할 뿐만 아니라 성형수축의 특성을 명확히 파악하는 것이 필요하다. 본 연구에서는 유리섬유로 보강된 폴리카보네이트를 이용하여 2.5차원형상인 환상형상의 시편에서 보이는 성형수축 현상을 조사하였다. 환상시편은 외경의 크기와 두께를 달리하여 설계하였다. 성형조건은 수지온도, 보압시간 및 보압크기를 변수로 설정하였다. 여러 성형조건으로 성형된 시편에서 내경과 외경의 크기가 변하는 양상에 대해서 분석하였다. 성형된 시편의 외경과 내경의 치수는 금형의 치수보다 작게 나타났다. 시편의 외경이 클수록, 그리고 시편의 두께가 두꺼울수록 수출율은 작게 나타났다. 또한 게이트의 위치에 따라 수축의 크기가 방향성을 보였다. 따라서 성형된 시편은 원형이 아니라 타원형으로 나타났고 게이트 방향으로 내경과 외경이 가장 큰 수축을 보였다. 수축된 제품의 형상조절을 위해서는 게이트 설계와 같은 금형설계가 중요하다고 판단된다.

• 한국생산제조학회지
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• 제20권1호
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• pp.34-39
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• 2011

Temperature control of a rubber injection mold is important for the dimensional accuracy of product. The main objective of this paper is to optimize the arrangement of heaters by FEM and optimal design method. Firstly, 3-dimensional transient heat transfer analysis was carried out for a square specimen mold. Results of FE analysis are a good agreement with the experimental results, showing about 1.22~7.22% error in temperature distribution. Secondly, we suggested the optimal method about an arrangement of heaters of rubber injection mold by using the optimal design technique. Distances between heater's center and the contact surface of mold, distances between heater's center and symmetric surface were considered as design variables. And the variances between the temperatures of cavity surfaces and their average temperature were used as the objective functions. Applying the optimal solution, the temperature variation was improved about 52.9~88.1 % compared to the existing mold. As a result of sensitivity analysis for design variables, design variables parallel to the direction of the split plane in mold affect the largest on the surface temperature variation in mold cavity.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.523-526
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• 1997

Sheanng is one of the most important operating processes in the field of sheet metal manufacturing. Compared with casting, forging and machining, shearing is very economical to obtain the desired shape. In recent years there has been increasing the use of shearing process in the manufacturing of small and light electronic components. In this paper, it has been researched the experimental investigation to examine the mfl uence of shearing process parameters such as clearance and lower holder configuration. Through the experiment results, the more narrow clearance gives the smaller burr height and the removal of lower holder makes the worse sheared surface. And FE simulation of shearing process using DEFORM-2D were camed out and the results compared w~th experimental studies

• 소성∙가공
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• 제20권6호
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• pp.450-455
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• 2011

This paper presents an inverse design methodology for the cross section geometry of mold spring with a rectangular cross section as the starting material for a coiling process. The cross-sections of mold springs are universally rectangular, as the parallel sides minimize the possibility of failure under high service loads. Pre-coiled wires are initially designed to have a trapezoidal cross section, which becomes a rectangle by the coiling process. This study demonstrates a numerical exercise to predict changes in the sectional geometry in spring manufacture and to obtain the initial cross section which becomes the exact rectangle desired from the manufacturing process. Finite element analysis was carried out to calculate the sectional changes for various mold springs. Geometrical parameters were the widths at inner and outer radii, the inner and the outer corner radii, and the height. A partial least square regression analysis was carried out to find the main contributing factors for deciding initial design values. The height and the width mainly affected various initial parameters. The initial width at the inner radius was mostly affected by various specification parameters.