• The Korean Journal of Rheology
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• v.7 no.3
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• pp.237-249
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• 1995

폴리우레탄 미세포 포움의 가공에 대한 연구를 수행하였으며 기체 과포화 수지 내 의 핵생성율을 증진시키기 위하여 폴리올과 이소시아네이트의 혼합물에 초음파 가진을 적용 하였다. 미세포 구조는 고압에서 질소 가스로 폴리올을 과포화ㅣ키고 폴리우레탄의 두 성분 을 충돌혼합시킨 직후 초음파에 의해 기포를 생성시켜 이루어진다. 낮은 포화 압력에서 질 소에 의해 포화된수지의 핵생성율을 증가시키기위하여 초음파 가진을 적용하였다. 확산에 의해 기포의 성장이 조절된다고 가정하고 금형이 충전되는 동안에 금형 내부에서의 기포성 장기구를 이해하기 위하여 수치적인 방법으로 이론적 연구를 수행하였다. 경화 시간과 확산 경계를 고려하여 최종적인 기포의 크기를 계산하였으며 반응속도론을 고려하여 중합반응 동 안의 폴리우레탄의 점도의 변화를 예측하고 경화 시간을 결정하였다. 이론적 및 실험적으로 결정된 기포의 수를 기준으로 하여 확산 경계를 예측하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.556-561
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• 2007

The rapid thermal response(RTR) molding is a novel process developed to raise the temperature of mold surface rapidly in the injection stage and then cool rapidly to the ejection temperature by air or water. The objectives of this paper are to investigate the effect of mold temperature, pressure and thickness of micro pattern molding and to provide a optimization of RTR injection molding for micro pattern from Moldflow simulation. Optimal minimum temperature and pressure was found without shortcut according to thickness. Filling percentage was influenced by glass transition temperature with the kinds of resin. Optimal temperature is slightly higher than glass transition temperature irrespectively of pressure, thickness, the kinds of resin in the micro pattern molding.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.518-520
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• 2011

금속분말 쾌속조형법의 한 종류인 DMLS 공정은 사출성형품의 균일한 냉각이 가능한 3차원 냉각시스템을 포함한 코어, 캐비티 제작이 가능하다. 그러나, 코어 및 캐비티 내 미세형상의 경우 DMLS로 제작하기에는 난해하므로 별도 미세 절삭가공을 통해 제작할 필요가 있다. 따라서, 본 연구에서는 DMLS금형강 소재의 미세 절삭가공 특성을 분석하고자 하였으며, 이를 위하여 HIP 공정 적용 전 후 DMLS금형강 소재를 대상으로 미세 절삭가공 실험을 수행하고 버 발생 및 공구마모 경향을 분석하였다. 실험 결과 HIP 적용 전 시편이 강도 및 조직측면에서 미세 절삭가공에 상대적으로 유리함을 확인할 수 있었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.1039-1042
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• 2000

This research will deal with Innovative manufacturing technology for milli-structure manufacturing technology which is located betweon the traditional manufacturing technology for macro-sized structure and the recently emerging manufacturing technology for micro-scaled structure such as MEMS. There are four fields in this research, which are micro-sheet metal forming technology, micro-bulk forming technology micro-molding technology and micro die making technology. As a project for new-technology in next generation, this research will be carried out through three terms and each term and be composed of three years.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1119-1123
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• 2008

High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a noncontact procedure. It has been recently applied to the injection molding of thin-walled parts or micro/nano structures. Though the induction heating has an advantage in terms of its rapid-heating capacity on the mold surface, it still has difficulty in efficient mold temperature control due to the restriction of an induction coil design suitable for the given mold shape. The present study proposed a localized mold heating method by means of selective use of mold material. For localized induction heating, an injection mold composed of ferromagnetic material and paramagnetic material is used. The electromagnetic induction concentrates on the ferromagnetic material, from which we can selectively heat for the local mold elements. The feasibility of the proposed heating method is investigated through an experimental measurement in terms of the heating efficiency on the localized mold surface.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.267-270
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• 2004

In Micro injection process, it is needed to the technique of making micro die, Rapid Thermal Pressing (RTP) and other techniques. Those techniques are independent. But the mutual connected system of techniques is needed. The target of this paper is the design of micro mold and the development of the entire micro injection techniques for functional polymer.

• Design & Manufacturing
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• v.10 no.3
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• pp.8-13
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• 2016

Despite technological advance, there have been several troubles in photo reaction injection molding (photo RIM) to produce ultra thin light guide panels (LGPs). In this study, micro leakage problem at cavity edge during photo RIM was investigated numerically. In order to obtain optimal processing conditions, we regulated inlet pressure of injected resin at the cavity edge and figured out micro leakage behaviors. At low inlet pressure (less than 100 Pa), though the micro leakage problem was not occurred, another problem, short shot due to not enough driving force, was appeared More than 1,000 Pa of the inlet pressure, injected resin was rapidly leaked through the micro gap at the cavity edge. Finally, we obtained optimal inlet pressure around 600 ~ 1,000 Pa. At this region, injected resin fully filled the cavity without micro leakage behavior. Based on the present study, further comparative investigations with experimental photo RIM should be performed to find optimal processing conditions for produce ultra thin LGPs.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.168-171
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• 2009

High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a non-contact procedure. Though the induction heating has an advantage in terms of its rapid-heating capacity on the mold surface, it still has a restriction on mold temperature control due to geometric restriction of an induction coil according to the mold shape. It has been recently applied to the injection molding of thin-walled parts or micro/nano structures. For localized induction heating, an injection mold composed of ferromagnetic material and paramagnetic material is used. The electromagnetic induction concentrates on the ferromagnetic material, from which we can selectively heat for the local mold elements. The present study proposed a localized induction heating method by means of selective use of mold material. The feasibility of the proposed heating method is investigated through the comparison of experimental observations according to the mold material.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1129-1131
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• 2008

We injection molded a plate with micro surface features including micro prizms & micro channels patterns on its surface and investigated the replication of the micro features depending on the mold temperature which is one of typical process parameters. The size of the patterns were 8um, 10um, 15um of prizm features & 15um, 30um, 45um of channel features. The size of the plate is about $400mm{\times}400mm$ and the thickness is 1mm of plate. the repliction of the mucro features turned out to depend on the mold temperature and also the location on the plate. The pressure and the feature of the melt in the cavity were also measured in real-time for the investigation on the micro feature replication.

• Journal of Korea Foundry Society
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• v.24 no.3
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• pp.153-158
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• 2004

본 연구에서는 기존 고압주조법의 해결과제인 고속충진 시 혼입되는 금형 cavity 내부의 유해 gas에 의한 gas porosity를 제어하기 위한 고속 사출 전 진공시스템 설계와 응고과정에서 발생되는 응고수축에 의한 shrinkage를 효과적으로 제어하기 위한 국부가압 스퀴즈의 조합시스템의 설계로 최적의 기계적 성질을 갖는 부품을 제조할 수 있는 공법을 개발하였다. 또한 개발된 신공법으로 자동차용 고내마모성 요구부품인 Reaction Shaft Support에 기존의 주철제를 대체하는 Al-15wt.%Si 과공정합금을 적용하여 시제품을 제조하였으며, 기존의 공법과 비교한 결과, 내부 porosity가 없는 미세하고 균일한 공정 및 초정 Si의 미세조직을 얻을 수 있었고, 기계적 특성평가에서도 매우 우수한 결과를 얻을 수 있었다.