• 한국정밀공학회지
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• 제13권1호
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• pp.78-83
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• 1996

This paper presents the characteristics of surface roughness and cutting force in ultraprecision cutting of aluminium alloy using natural diamond tools whose edge radii are smaller than those of tools made of other materials. The feed rate and depth of engagement were set to be a micrometer order. After measuring the surface roughness of machined surface and cutting force for each cutting condition, the relations between the surface quality and its condition were investigated qualitatively. If the feed rate was under a certain limit, the machined surface quality was deteriorated unexpectedly. This is supposed to have happened due to vibration leading its condition to abnormal one. In a certain situation the machined surface roughness by a natural diamond tool was inferior to that made by a carbide tool whose cutting edge radius is larger. This is supposed to be caused by not normal machining but burnishing effect.

• 한국기계가공학회지
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• 제6권3호
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• pp.65-70
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• 2007

Generally, the core component of small precise optical device demands high accuracy of manufacturing processes. Although, the geometry of it is simple, the manufacturing technique to materialize is categorized as the ultra-precision machining and it must be done with the specialized machines and by the trained operator. Typical examples of small precise optical device are laser printer and phone camera. As a core part of laser printer, polygon mirror is used in laser scanning unit(LSU). It couldn't be fabricated with conventional machine but specified machine for polygon mirror machining. In this study, Polygon mirror with 16 surfaces was manufactured in the process of ultra-precision fly-cutting with Al material and investigated optimum machining conditions in terms of feedrate, pitch per cycle and depth of cut. Owing to process of polishing has bad influence on reflection angle, surface roughness, $R_{max}$=10nm, and form error, $Ra={\lambda}/10({\lambda}=632nm)$, are prerequisites for polygon mirror.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1990년도 제12회 학술강연회초록집
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• pp.69-72
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• 1990

최근의 전자및 광학기기 분야에 있어서의 준부신 발전은 다면경 가공기나 초정밀 절삭, 연삭기와 같은 초정밀 가공기계의 개발과 실용화에 힘입은 바 크다. 이러한 초정밀 가공기의 성능을 좌우하는 핵심 요소로서 주축계를 들 수 있으며, 비교적 소형 경량의 공작물을 가공하는 기계의 주축용 베어링으로는 볼 베어링이나 오일 베어링을 대신하여 공기베어링이 점차 널리 사용되고 있다. 일반적으로 주축으로 사용되는 베어링은 원통형 레이디얼 베어링과 원판형 스러스트 베어링이 결합된 형식이 주류를 이루나 이러한 베어링은 스러스트 판과 축의 직가곧 가공오차가 존재하기 때문에 가공하기는 쉬우나 회전시에 의의 영향에 의해 회전 정밀도 유지가 어렵다는 단점을 지니고 있다. 이러한 단점을 보완하기 위하여 사용되는 베어링에는 원추형(conical) 베어링과 구면형(spherical) 베어링이 쓰이고 있다. 이러한 원추형 베어링과 구면형 베어링은 가공오차를 베어링과 축의 현압 연마로써 없애줄 수 있으며 베어링이 축방향 하중과 경방향 하중을 동시에 지지하여 줌으로써 기계 전체의 부피를 줄이고 회전 정밀도를 향상시켜 주는 것으로 알려져 있다. 그러나 구면의 베어링 간극을 정확히 가공하기 어려운 단점이 있어 축과 베어링을 현압연마하여 가공한 후에 두부품을 중심선상에서 분리시키므로써 요구되는 간극을 얻을 수 있는 원추형 베어링이 많이 쓰이고 있다. 본 연구에서는 직접 수치 해법을 이요하여 원추형 베어링의 유막내의 압력 분포를 계산하고 이 합력인 하중지지 용량이 축방향 하중과 경방향 하중을 지지하는 특성을 이론적으로 검토하여 외부 가압 원추형 베어링으 특성수를 파악하여 설계자료를 제시하고자 한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.97-98
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• 2010

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.34-34
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• 2004

정보의 급속한 발전, 컴퓨터, 가전기기, 자동차등 내구 소비재의 제품 개발기간 단축, 생산자의 지속적인 생산성 향상 활동, 소비자 선호의 다양성, 품질 요구 수준 상승 등 제반 환경변화는 절삭가공부분에 있어 핵심이 되고 있다. 여기에 전통적 제조업의 고부가가치화 및 새로운 시스템의 도입 등과 맞물려 최근의 초정밀 공작기계는 고속화, 고정밀화를 바탕으로 크게 발전하고 있다, 특히 21세기로 향하는 지금 공작기계 기술은 고속화, 정밀화, 개방화, 환경친화의 방향으로 혁신을 지속하고 있으며, 머지 않아 마이크로 프로세서의 급속한 발전에 힘입어 고속화 기술은 극 초고속화 단계로, 정밀화 기술은 극 초정밀화 단계로, CNC 기술은 오픈화 및 네트워크화를 통한 다양한 통신기술이 부가됨으로써 설계, 생산, 영업 및 서비스 정보와 연계시켜 통합제어를 통한 타 지역의 공작기계를 원격제어 할 수 있는 단계로 이르게 될 것이다.(중략)

• 한국정밀공학회지
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• 제26권6호
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• pp.42-49
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• 2009

The optical elements made of plastics are normally produced by mass production such as injection molding with use of precision dies and molds. It costs to prepare the dies and molds, and it is only justified to prepare such expensive dies and molds when the parts are massively produced. On the other hand, it is too expensive and inefficient when precision plastic parts are needed only in small quantities, such as a case of trial manufacturing of new products. An ultra-precision diamond cutting is one of promising processes to produce the precision plastic parts in such cases. But it is commonly believed that an ultra-precision cutting of plastics for optical components is very difficult, because they are thermo-plastic material. In the present research, an ultra-precision diamond cutting of polycarbonate (PC), that is one of typical optical materials, was tried by using elliptical vibration cutting method. It is experimentally proved that good optical surfaces were obtained by using elliptical vibration cutting in cases of grooving and flat surfaces. The maximum surface roughness of less than 60 nm in peak to valley value is acquired.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.261-264
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• 2004

This paper presents the design and test of elliptical vibration assisted cutting tool post. It is actuated by two piezoelectric actuators which are connected to the moving part through the elastic hinge with its role of imposing the preliminary pressures. These two actuators are located at right angles so that the resulting tool tip moves like a two-dimensional ellipse. Also, the tool post is activated within the region of linear actuation in order to overcome the distorted elliptical motion. For the precise measurement of the displacement of the tool tip, three-dimensional experimental apparatus was designed and the strokes of the tool post in major and minor axes were measured. The results show that the tool post can produce the variety of vibration locus from a circle with a radius of 5 ${\mu}{\textrm}{m}$ to an ellipse with a major axis, a =10 ${\mu}{\textrm}{m}$, and a minor axis, b =2.5 ${\mu}{\textrm}{m}$

• 한국정밀공학회지
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• 제24권11호
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• pp.52-58
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• 2007

A cutting device capable of generating various shapes of the cyclic elliptical trajectory of a cutting tool was proposed and micro v-grooving experiments were performed to investigate the characteristics of elliptical vibration cutting (EVC). The proposed cutting device is comprised of a pair of parallel piezoelectric actuators with which harmonic voltages of varying phase difference and magnitude are supplied, creating various shapes of the elliptical tool path. The attributes of the elliptical locus involving the direction of the axis of an ellipse, the rotational direction and amplitudes of a trajectory were fine-tuned for stable operation of the EVC. The EVC characteristics performed with brass and copper revealed reduction in the cutting resistance and suppression of burr formation, resulting in the enhancement of form accuracy of machined micro-features. While the effect of the EVC increases with the increase of excitation frequency and the amplitude, it is found that a change in the cutting force decreases as the amplitude of an elliptical locus increases.

• 한국정밀공학회지
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• 제25권6호
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• pp.40-46
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• 2008

Ultraprecision cutting of steels with geometrically defined single crystal diamond tools is handicapped by excessive tool wear. This paper presents a new approach to suppress the wear of single crystal diamond tool in cutting of steels. In general, it is said that the wear of diamond tool is caused by chemically reactive wear under high temperature and high pressure conditions. In order to suppress such chemical reactions, the time of contact between the diamond tool and the steel work in cutting was controlled by employing the intermittent cutting method such as fly-cutting. Series of intermittent cutting experiments have been carried out to control the tool-work contact time by changing one cycle of cutting length and cutting speed. The experimental results were shown that the tool wear was much dependent on the contact time regardless of the cutting speed, and that the wear was much suppressed by reducing the tool-work contact time. It is expected that the steels can be successfully cut with a single crystal diamond tool by controlling the contact time.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.414-417
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• 2005

Single point diamond turning technique for optical crystals is studied in this paper. The main factors which are influential the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability. The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. The purpose of our research is to find the optimal machining conditions for ductile cutting of optical crystals and to apply the SPDT technique to the manufacturing of ultra precision optical components of brittle material(Ge). Many technical challenges are being tried for the large space infrared telescope, which is one of the major objectives of the National Strategic Technology Road Map (NSTRM).