• 폴리머
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• 제32권6호
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• pp.501-508
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• 2008

렌즈나 휴대폰 부품 같은 소형 플라스틱 부품들은 일반적으로 다수 캐비티 사출금형에서 성형된다. 이러한 다수 캐비티 금형에서의 사출성형은 캐비티간의 충전 불균형이 일어날 수 있다. 이러한 충전 불균형 현상은 제품의 치수 및 중량의 편차뿐 아니라 제품의 물리적 특성에도 영향을 미친다. 충전 불균형은 무엇보다도 기하학적으로 균형 잡히지 않은 delivery system의 설계에서 기인된다. 하지만 delivery system이 기하학적으로 균형 있게 설계가 되었다 하더라도 충전 불균형 현상은 여전히 발생된다. 이러한 현상은 런너 단면에서의 온도분포에 기인하며 사출성형 공정 중 사출속도에 크게 영향을 받는 것으로 본 연구에서 파악되었다. 즉 충전 불균형은 부적절한 사출 성형 공정에 의해 발생되며 성형 공정 조건 중 사출속도는 충전에 영향을 주는 매우 중요한 요소이다. 본 연구에서는 재료와 사출 속도에 따른 충전 불균형 현상을 실험과 CAE을 통하여 관찰하였다. 사출속도 변화에 따른 충전 불균형 때문에 시편의 치수 및 무게가 불균일함을 확인하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.137-140
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• 2005

Resin transfer molding (RTM) is one of the most popular processes for producing fiber reinforced polymer composites. In the manufacture of complex thick composite structures, analysis on flow front advancement on the resin impregnating the multi-layered fiber preform is helpful for the optimization of the process. In this study, three-dimensional mold filling simulation of RTM is carried out by using CVFEM (Control Volume Finite Element Method). On the assumption of isothermal flow of Newtonian fluid, Darcy’s law and continuity equation are used as governing equations. Different permeability tensors employed in each layer are obtained by experiments. Numerically predicted flow front is compared with experimental one in order to validate the numerical results. Flow simulations are conducted in the two mold geometries, rectangular plate and hollow cylinder. Permeability tensor of each layer preform in Cartesian coordinate system is transformed to cylinder coordinates system so that the flow within the multi-layered preforms of the hollow cylinder can be calculated exactly. Our emphasis is on the three dimensional flow analysis for circular three-dimensional braided preform, which shows outstanding mechanical properties such as high impact strength and toughness compared with other conventional two-dimensional laminar-structured preforms.

• 한국생산제조학회지
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• 제23권3호
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• pp.291-298
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• 2014

This study uses two numerical approaches to analyze the filling behavior of micro patterns on micro-injection molding for V-grooves pattern which cannot be simulated with conventional CAE packages. The parametric studies have been performed to examine the fidelity of micro patterns with respect to temperature, pressure, inlet velocity and pattern location on the mold according to the boundary condition from the macro pressure and velocity data which can be obtained by conventional CAE packages. Through these numerical approaches, the filling behavior of polymer melt in micro patterns can be understood, the quality of replication can be predicted, and the V-groove pattern can be shaped uniformly during the process of injection molding.

• 한국정밀공학회지
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• 제19권11호
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• pp.83-88
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• 2002

In order to predict the moldability of a injection molded part, a simulation of filling is needed. Short shot is one of the most frequent troubles encountered during injection molding process. The adjustment of process conditions is the most economic way to troubleshoot the problematic short shot in cost and time since the mold doesn't need to be modified at all. But it is difficult to adjust the process conditions appropriately in no times since it requires an empirical knowledge of injection molding. In this paper, the intelligent CAE system synergistically combines fuzzy-neural network (FNN) for heuristic knowledge with CAE programs for analytical knowledge. To evaluate the intelligent algorithms, a cellular phone flip has been chosen as a finite element model and filling analyses have been performed with a commercial CAE software. As the results, the intelligent CAE system drastically reduces the troubleshooting time of short shot in comparison with the experts' conventional methodology which is similar to the golden section search algorithm.

• 한국정밀공학회지
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• 제18권12호
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• pp.124-129
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• 2001

Recently, life cycle and lead-time of products have been shortened with the demand of customers. Therefore, it is important to reduce time and cost at the step of manufacturing trial molds. High speed machining can be applied for this kind of purpose with a lot of practical advantages. In our research, several fundamental experiments are carried out to obtain machining parameters such as cutting force, machining time and surface characteristics for tool paths that are appropriate to high-speed machining. Moreover, a trial mold for an automatic transmission knob is fabricated with aluminum-7075 material. Using automatic set-up equipments, an ABS rapid prototype of a trial product of an AT knob is also manufactured with a filling process.

• 유변학
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• 제11권2호
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• pp.159-167
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• 1999

샌드위치 사출성형 공정은 기존의 사출성형 공정이 가지지 못하는 여러 장점들로 인해 최근 산업적으로 주목 받고 있는 고분자 가공 공정이다. 이 공정의 해석적인 접근은 거의 불가능하므로, 본 연구에서는 수치모사를 통해서 샌드위치 사출성형의 충전 공정을 연구하였다. 수치모사는 기본적으로 유한요소법을 사용하였고 Flow Analysis Network(FAN)/관할체적(Control Volume)법 등을 함께 이용하였다. 그리고 skin polymer의 선단을 확인할 수 있는 기존의 충전율 변수와 함께 skin polymer와 core polymer의 경계를 표시하는 새로운 충전율 변수를 도입하였고 이것을 이용하여 core polymer의 선단을 추적하였다. 새로운 충전율 변수는 두께 방향으로 온도장을 풀기 위해 나눈 각 층에서 정의되었다. 수치모사에 사용된 skin polymer와 core polymer로는 물성이 다른 두 고분자 물질을 주입시켜서 나타나는 충전 형태를 비교했다. 즉, 점도 상수, power-law 지수 등과 같은 유변 물성이 다른 두 고분자 물질을 충전시키기 위해 공정상 필요한 입구에서의 압력 등을 계산했으며 나중에 들어가게 되는 core polymer의 충전 완료 후 금형 내에서의 두께 방향과 흐름 방향으로의 분포 등을 구하였다. 또한 실제 공정 상에서 가공조건에 해당되는 switchover time과 벽 온도 등의 조건을 바꿔가면서 수치모사를 진행하였다. 사례 연구를 통하여 얻어진 물성과 가공 조건에 따른 core polymer의 충전 형태와 입구에서의 압력 등은 샌드위치 사출성형의 산업적 이용에 매우 유용하게 사용될 수 있다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.284-287
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• 2002

During resin transfer molding(RTM) process, in case of thick parts, resin flow and void formation should be modeled three dimensionally even though for parts of small thickness, resin flow and void formation can be modeled two dimensionally. In this study, numerical simulations of three dimensional mold filling and void formation during RTM process.

• 소성∙가공
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• 제14권2호
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• pp.112-120
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• 2005

In the die casting process, the flow of liquid metal has significant influence on the quality of casting products and die life. For the optimal process design of gear housing of automobile transmission, various analyses were performed in this study by using computer simulation code, MAGMAsoft. The simulation has been focused on the molten metal behaviors during the mold filling and solidification stages for the sound casting products. Also internal defects were predicted by application of air pressure and feeding criteria.

• 한국공작기계학회논문집
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• 제10권2호
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• pp.64-72
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• 2001

Weld line is one of serious troubles which are observed in a plastic part manufactured by a injection molding process. This is caused by many process factors, which are molding pressure, temperature, velocity, location of a injection gate, mold geometry and material properties. investigation on the effects of these process factors to the appearance of a weld line was carried out using a finite element method. Filling and packing analyses were carried out by modifying both the configuration of the injection gates and cavity thickness. Proper locations of the injection gates could be determined by considering molding pressure, temperature, velocity and frozen layer, and whereby the weld line was controled. In order to make a weak appearance of the weld line, flow velocity and flow front in a cavity were also investigated by modifying a cavity thickness. As a result, flow front was extended around the corner in the cavity by changing the flow velocity and hence the appearance of the weld line was much weakened.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.47-52
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• 2001

Micro-injection molding and microfluidic devices with the help of MEMS technologies including the LIGA process are expected to play important roles in. micro-system industries, in particular the bioapplication industry, in the near future. Understanding fluid flows in micro-channels is important since micro-channels are typical geometry in various microfluidic devices and mold inserts for micro-injection molding. In the present study, both experimental and numerical studies have been carried out to understand the detailed flow phenomena in micro-channel filling process. Three sets of micro-channels of different thickness were fabricated and a flow visualization system was also developed to observe the filling flow into the micro-channels. Experimental flow observations were extensively made to find the effects of channel width and thickness, and effects of surface tension and volume flow rate and so on. And a numerical analysis system has been developed to simulate the filling flow into micro-channels with the surface tension effect taken into account. Discussed are the flow visualization experimental observations along with the predictability of the numerical analysis system.