• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.9 no.4
• /
• pp.38-43
• /
• 2010

By generating 2-directional vibration in a xy plane of workpiece table, a newly developed micro drilling using 2-directional vibration was carried out. The vibration was produced by applying sinusoidal voltages to the orthogonally arranged piezoelectric materials built in the workpiece excitation table. Through the micro-drilling experiments using poly-carbonate and brass material, it was found that micro drilling using 2-directional vibration in a workpiece table could be an efficient method to enhance the form accuracy of machined workpiece by suppressing burr formation at both entry and exit region. A higher form accuracy could be obtained by increasing stiffness of feeding mechanism, decrease of geometric tolerance of combining jig, and development of high performance excitation table which generates amplified vibration at higher frequency.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.9
• /
• pp.109-117
• /
• 2003

With development of high advanced technologies and skills, micro machining techniques also are being more functional and smaller. Some of the recently developed micro machining technologies are micro drilling, micro EDM, WEDG, LBM, micro milling, micro UVM etc. In these micro machining techniques, Micro -EDM is generally used for machining micro holes, pockets, and micro structures in difficult-cut-materials. For machining micro structures, first of all, tool electrode should be fabricated by WEDG process. In micro-EDM, parameters such as peak current, pulse width, duration time are very important to fabricate the tool electrode and micro structures. Developed experimental equipments are composed of RLC circuit with PWM. In this paper, using developed micro EDM machine, the characteristics of micro electro discharge machining are investigated at micro holes, slot, and pocket machining etc. Also the trends of tool wear are investigated in case of hole and slot machining.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.3
• /
• pp.315-322
• /
• 2011

High-accuracy micropatterns such as V-shaped microgrooves are increasingly in demand for various engineering areas. And the technical trend goes for large surface areas in precision machining technology. So micropatterns with large surface areas are expected to play an increasingly important role in today's manufacturing technology In this study, we focused on developing machining technologies. First, a machine vision system for precise tool setting is developed. Second, an on-machine measurement (OMM) system for large-area measurement is implemented. And also software for tool path generation and simulation is developed. With these technologies we fabricated large-surface micropatterns in an electroless nickel-plated workpiece with single-crystal diamond tools and a 32-in, $675mm{\times}450mm$ mold with tens of V-and pyramid-shaped micropatterns.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.472-473
• /
• 2008

Flow boiling in parallel microchannels has received attention as an effective heat sink mechanism for power-densities encountered in microelectronic equipment. the bubble dynamics coupled with boiling heat transfer in microchannels is still not well understood due to the technological difficulties in obtaining detailed measurements of microscale two-phase flows. In this study, complete numerical simulation is performed to further clarify the dynamics of flow boiling in microchannels. The level set method for tracking the liquid-vapor interface is modified to include the effects of phase change and contact angle. The method is further extended to treat the no-slip and contact angle conditions on the immersed solid. Also, the reverse flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of channel shape and inlet area restriction on the bubble growth, reverse flow and heat transfer are quantified.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.6 no.3
• /
• pp.58-64
• /
• 1997

A micromechanics model to describe the elastic behavior of fiber or whisker reinforced metal matrix composites was developed and the stress concentrations between reinforcements were investigated using the modified shear lag model with the comparison of finite element analysis (FEA). The rationale is based on the replacement of the matrix between fiber ends with the fictitious fiber to maintain the compatibility of displacement and traction. It was found that the new model gives a good agreement with FEA results in the small fiber aspect ratio regime as well as that in the large fiber aspect ratio regime. By the calculation of the present model, stress concentration factor in the matrix and the composite elastic modulus were predicted accurately. Some important factors affecting stress concentrations, such as fiber volume fraction, fiber aspect ratio, end gap size, and modulus ratio, were also discussed.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2009.05a
• /
• pp.211-211
• /
• 2009

높은 이온화율과 복잡한 형상의 모재에도 표면 도포성 및 균일성을 나타내는 아크이온플래이팅 기술과 비전도성 세라믹 타겟물질에 적용가능한 스퍼터링 기술이 결합된 하이브리드 코팅 시스템(Hybrid coating system)을 이용하였다. 그리고 Cr-Al-N과 Cr-Si-N 코팅막의 강화 기구를 복합시킨 새로운 개념의 Cr-Al-Si-N 코팅막을 초경(WC-Co)시험편에 증착하여 Si 첨가량에 따른 미세구조의 미세경도 특성을 파악하였다. 공구성능 평가는 고속가공조건하에 마이크로 밀링기에서 무코팅(초경공구), Cr-Al-Si-N (Si : 0, 4.5, 8.7, 16 at.%) 코팅 마이크로엔드밀에 대하여 공구마멸에 대한 공구수명을 비교, 평가하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.229-230
• /
• 2006

Shape memory alloy, Nitinol is used for medical stent, artificial human joint, antenna of artificial satellite, fire door, temperature sensor...etc. It is important for some nitinol product high precision and clean surface. In this study, we experiment about deburring of edge and surface of nitinol work piece with micro electrolytic-deburring. We made an observation in case electric currents are $1A{\sim}4A$, above 5A and each machining times.

• Journal of the Korean Vacuum Society
• /
• v.2 no.1
• /
• pp.99-108
• /
• 1993

저압화학증착법에 의해 제조된 hemispheircal 및 rugged Si 박막들은 64 Mbit DRAM 이상의 캐패시터에 사용하기 위해 개발되었다. 이 공정을 사용하므로써 종래에 사용되던 Si 전극의 평평한 표면이 hemispherical 혹은 rugged 박막 형태의 표면으로 변한다. 위와 같은 박막은 비정질 Si 표면에서 핵생성되며 Si 원자 확산에 의해 결정립들이 결정체로 성장한다. 화학증착의 변수, 열처리 및 in-situ doping process들은 hemispherical 및 rugged Si 박막의 미세구조에 영향을 준다. 동일 두께에서는 고온에서 이루어질 때 혹은 동일 온도일 경우에는 얇은 박막층일 때에 하부전극의 표면들이 rugged poly Si 형상을 나타내며 이렇게 됨으로써 유효면적은 2.1배로 증가한다. 이와 같은 캐패시터 유효면적 증가는 대체로 높은 신뢰성을 갖는 두꺼운 절연막을 사용하면서 stack 캐패시터 구조의 높이를 감소시킬 수 있다. 따라서 이러한 제조기술은 차세대 캐패시터에 적용될 수 있다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.10a
• /
• pp.326-331
• /
• 2000

This paper describes the statistical analysis techniques for the surface roughness assessment of polished surfaces. In experiments, the polishing process of the sample surfaces which are manufactured by ball end mill is consist of two steps; the cusp removal process and the surface finishing process. For the cusp removal process, the criterion of cusp removal was established from the power spectrum analysis to assess the change of the cusp removal rate. For the finishing process, the surface was polished by the rotational CBN tool and vibration wood tool. And the surface quality of polished surface was assessed using the functional parameters based on the statistical values of surface profiles. Consequently, the surface finish performance of the polished surface using the vibration wood tool was improved.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.05a
• /
• pp.159-159
• /
• 2004

금속 박막 위의 알칸티올분자의 흡착에 의한 자기조립단분자막(Self-Assembled Monolayers)은 접착 방지, 마찰 저하 등의 기능을 가진 코팅층으로서의 응용과 분자 또는 생분자의 미세 구조물 형성을 위한 방법으로 널리 연구되어지고 있다. 이러한 연구 중에서 특히 자기조립단분자막의 매우 얇은 두께와 금속 박막의 선택적 식각을 위한 안정적인 리지스트(Photo Resist)로서의 특징을 활용한 극미세 패터닝에 대한 연구가 활발히 진행되고 있다.(중략)