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박성진,권태헌,Park, Seong-Jin,Kwon, Tai-Hun 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.11
The cooling stage is the very critical and most time consuming stage of the injection molding process, thus it cleary affects both the productivity and the part quality. Even through there are several commercialized package programs available in the injection molding industry to analyze the cooling performance of the injection molding coling stage, optimization of the cooling system has npt yet been accomplished in the literature due to the difficulty in the sensitivity analysis. However, it would be greatly desirable for the mold cooling system designers to have a computer aided design system for the cooling stage. With this in mind, the present study has successfully developed an interated computer aided design system for the injection molding cooling system. The CAD system utilizes the sensitivity analysis via a Boundary Element Method, which we recently developed, and the well-known CONMIN alforuthm as an optimization technique to minimize a weighted combination (objective function) of the temperature non-uniformity over the part surface and the cooling time related to the productivity with side constranits for the design reality. In the proposed objective function , the weighting parameter between the temperature non-uniiformity abd the cooling time can be adjusted according to user's interest. In this cooling system optimization, various design variable are considered as follows : (i) (design variables related to processing conditions) inlet coolant bulk temperature and volumetric flow rate of each cooling channel, and (ii) (design variables related to mold cooling system design) radius and location of each cooling channel. For this optimum design problem, three different radius and location of each cooling channel. For this optimum design problem, three different strategies are suffested based upon the nature of design variables. Three sample problems were successfully solved to demonstrated the efficiency and the usefulness of the CAD system.
마이크로 채널 충전 과정의 유동 현상(I) - 유동 가시화 실험 -
김동성,이광철,권태헌,이승섭,Kim, Dong-Sung,Lee, Kwang-Cheol,Kwon, Tai-Hun,Lee, Seung-S. 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.10
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.
사출 성형된 일회용 카오스 마이크로 믹서의 개발: 나선형 라미네이션 마이크로 믹서 (I) - 디자인 및 수치 해석 -
김동성,이세환,권태헌,Kim Dong Sung,Lee Se Hwan,Kwon Tai Hun,Ahn Chong H. 대한기계학회 2005 大韓機械學會論文集A Vol.29 No.10
The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Serpentine Laminating Micromixer (SLM) in the present study, Part 1. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: splitting/recombination and chaotic advection. The splitting and recombination (in other term, lamination) mechanism is obtained by the successive arrangement of 'F'-shape mixing units in two layers. The chaotic advection is induced by the overall three-dimensional serpentine path of the microchannel. Chaotic mixing performance of the SLM was fully characterized numerically. To compare the mixing performance, a T-type micromixer which has the same width, height and length of the SLM was also designed. The three-dimensional numerical mixing simulations show the superiority of the SLM over the T-type micromixer. From the cross-sectional simulation results of mixing patterns, the chaotic advection effect from the serpentine channel path design acts favorably to realize the ideal lamination of fluid flow as Re increases. Chaotic mixing mechanism, proposed in this study, could be easily integrated in Micro-Total-Analysis-System, Lab-on-a-Chip and so on.
모듈화된 초소형 몰드 시스템(MSMS)을 이용한 다단 마이크로 구조물의 초소형 사출성형 공정
이봉기(Bong-Kee Lee),권태헌(Tai Hun Kwon) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.7
본 연구에서는 다단 마이크로 구조물의 대량성형을 위하여, 모듈화된 초소형몰드 시스템(MSMS)을 이용한 초소형 사출성형 공정을 수행하였다. 본 연구에서 적용된 초소형몰드 시스템은 여러 모듈들로 구성되어 있으며, 각 모듈들은 다양한 단면 마이크로 구조물을 가지고 있다. 초소형몰드 시스템의 모듈들은 X-선 리소그래피 공정 및 니켈 전주도금 공정으로 제작되었으며, 다양한 모듈들을 조합 및 결합함으로써 복잡한 형상을 가지는 초소형몰드 시스템을 효과적으로 구현할 수 있다. 이와 같은 초소형몰드 시스템을 적용함으로써, 본 연구에서는 다단 구조물의 표면에 마이크로 삼각 프리즘이 주기적으로 배열되어 있는 다단 마이크로 구조물의 초소형 사출성형 공정을 성공적으로 수행하였다. 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.
사출/압축 성형 Center-gated 디스크에서의 잔류 응력과 복굴절의 수치 해석(Ⅱ) - 공정조건의 영향 -
이영복(Young Bok Lee),권태헌(Tai Hun Kwon),윤경환(Kyunghwan Yoon) 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11
The accompanying paper. Part I, has presented the physical modeling and basic numerical analysis results of both the flow-induced and thermally-induced residual stress and birefringence in injection molded center-disks. The present paper. Part II, has attempted to investigate the effects of various processing conditions of injection/compression molding process on the residual stress and birefringence. The birefringence is significantly affected by injection melt temperature. packing pressure and packing time. Birefringence in the shell layer increases as melt temperature gets lower. The inner peak of birefringence increases with packing time and packing pressure. On the other hand. packing pressure, packing time and mold wall temperature affect the thermally-induced residual stress rather significantly in the shell layer, but insignificantly in the core region. Injection/compression molding has been found to reduce the birefringence in comparison with the conventional injection molding process. In particular. mold closing velocity and initial opening thickness in the compression stage of injection/compression molding process have significant effect on the flow-induced birefringence, but not on the thermal residual stress and the thermally induced birefringence.
모듈화된 초소형몰드 시스템(MSMS)을 이용한 다단 마이크로 구조물의 초소형 사출성형 공정
이봉기(Bong-Kee Lee),권태헌(Tai Hun Kwon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In the present study, microinjection molding process utilizing the newly developed micromold system (modularized & sectioned micromold system, MSMS) has been carried out for a replication of multi-level microstructures. The developed MSMS consists of several micromold modules, each having various crosssectional microstructures on its top surface. The micromold modules are precisely fabricated via a deep X-ray lithography and a subsequent nickel electroforming process. By combining and assembling various micromold modules, the MSMS containing a microstructured surface with complicated features is efficiently obtained. So obtained MSMS can be used as a mold system in micromolding processes for a mass replication of the complicated microstructured surfaces. In this manner, the multi-level microstructure like triangular prism microstructures on a stepped surface was successfully replicated by microinjection molding process.
사출 성형된 일회용 카오스 마이크로 믹서의 개발 : 나선형 라미네이션 마이크로 믹서 (Ⅱ) - 제작 및 혼합 실험 -
김동성(Dong Sung Kim),이세환(Se Hwan Lee),권태헌(Tai Hun Kwon),Chong H. Ahn 대한기계학회 2005 大韓機械學會論文集A Vol.29 No.10
In this paper, Part Ⅱ, we realized the Serpentine Laminating Micromixer (SLM) which was proposed in the accompanying paper, Part I, by means of the injection molding process in mass production. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms of splitting/recombination and chaotic advection by the successive arrangement of “F”-shape mixing units in two layers. Mold inserts for the injection molding process of the SLM were fabricated by SU-8 photolithography and nickel electroplating. The SLM was realized by injection molding of COC (cyclic olefin copolymer) with the fabricated mold inserts and thermal bonding of two injection molded COC substrates. To compare the mixing performance, a T-type micromixer was also fabricated. Mixing performances of micromixers were experimentally characterized in terms of an average mixing color intensity of a pH indicator, phenolphthalein. Experimental results show that the SLM has much better mixing performance than the T-type micromixer and chaotic mixing was successfully achieved from the SLM over the wide range of Reynolds number (Re). The chaotic micromixer, SLM proposed in this study, could be easily integrated in Micro-Total-Analysis-System, Lab-on-a-Chip and so on.