• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.1021-1028
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• 2015

Subminiature lenses are currently widely used in mobile phone cameras and are usually produced by injection molding. The lens molding process has the unique feature of a runner volume that is much larger than the part volume, and this feature should be considered when determining the mold design and molding conditions. In this study, a shell-type runner was proposed as an alternative to the conventional cylindrical runner used for lens molding. An injection molding simulation was performed by applying the proposed shell runner, and the simulation results were compared with those from the cylindrical runner case. It was found that the shell runner could considerably reduce the runner cooling time with only a slight increase in the injection pressure. The effect of the runner thickness was then investigated numerically in terms of the mold filling and cooling characteristics, from which an optimal runner thickness could be determined.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.859-866
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• 2010

In this study, microinjection molding process using the newly developed micromold system, namely modularized and sectioned micromold system (MSMS), has been carried out for a replication of multi-level microstructures. The present MSMS consisted of several micromold modules, each having cross-sectional microstructures on the top surface. The micromold modules were precisely fabricated by deep X-ray lithography and subsequent nickel electroforming. By assembling the micromold modules, an MSMS having multi-level microstructures, which could be used as a mold system in micromolding processes, was obtained. In this manner, polymeric multi-level microstructures, such as the triangular prism microstructures on a stepped surface, were successfully replicated by the microinjection molding process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.210-210
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• 2004

최근 광 디스크로부터 신호를 검출하고 기록하는 핵심장치인 장 Pick-up이 점차로 고기능화, 소형화, 경량화 되면서 광 기록장치들의 발전에 크게 기여하고 있다. 초소형, 초경량 광 Pick-up을 생산하기 위해서는 광 Pick-up의 무게와 크기에 큰 영향을 미치는 렌즈의 재료를 유리에서 플라스틱으로 전환하고, 비구면 렌즈를 사용하는 것이 필요하다. 플라스틱 비구면 렌즈를 대량 생산하기 위해서 가장 많이 사용되는 방법이 사출성형이고, 소형, 경량, 휴대기능을 강조하는 제품동향으로 인하여 플라스틱 렌즈의 주요 생산기술인 사출성형의 중요성이 날로 부각되고 있다.(중략)

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.287-290
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• 2001

최근 정보통신 산업의 급속한 발전으로 이동 통신용 단말기 및 반도체 칩 케리어 등의 플라스틱 부품의 초소형 경량화 요구가 증대되고 있다. 미세 사출성형용(micro injection molding) 박판의 사출을 위한 미세사출 성형 고분자 재료는 매우 우수한 용융 유동 특성을 가져야 하고, 반도체나 소형 엔지니어링 부품으로 사용하려면 높은 인장강도, 충격강도 및 치수안정성을 가져야 한다. (중략)

• Journal of the Korean Society for Precision Engineering
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• v.32 no.11
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• pp.961-968
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• 2015

This study aims to develop an efficient mold structure for the injection molding of a subminiature lens, using shell-type runners instead of traditional cylindrical runners. While the shell runner has the advantage of shorter cooling time due to its thinner geometry, this smaller thickness causes an increase in injection pressure. In this study, the design of the shell runner was modified to contain multiple holes for the purpose of reducing injection pressure. Numerical analyses were performed for shell runners of various hole-shapes, and the resulting filling and cooling characteristics were discussed; the rhombic hole showed the best result for both filling and cooling characteristics. Subsequently, injection molding experiments were performed using an injection mold fabricated based on the rhombic design. The lens parts were successfully molded with highly-reduced cycle time and without degradation of part quality.

• Proceedings of the KSME Conference
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• 2001.06c
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.1982-1988
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• 2002

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 bio-application 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, Part 1, an experimental investigation has been carried out to understand the detailed flow phenomena in micro-channel filling process. Three sets of micro-channels of different thickness (40um,30um and 2011m) were fabricated using SU-8 on silicon wafer substrate. And a flow visualization system was developed to observe the filling flow into the micro-channels. Experimental flow observations are extensively made to find the effects of pressure, inertia force, viscous force and surface tension. A dimensional analysis for experimental results was carried out and several relationships A dimensionless parameters are obtained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.12-18
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• 2009

In this paper, for reducing the assembly torque of subminiature plastic barrel and base which are the essential parts of mobile phone camera module, the high-precision system for inspecting the screw shape of core, electrode and injection molding products was developed. For realization of inspection process, the inspection parameters for evaluating the manufacturing quality were selected and the measurement methods of selected parameters were developed. Finally, the inspection system which is possible to be applied to the field were fabricated.