• Design & Manufacturing
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• 제6권1호
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• pp.24-28
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• 2012

Friction and wear affect all processes involved in the extraction of materials and their conversion into finished products in the die applications such as drawing, extrusion etc. Originating phenomenon from the contact surface between the tool and workpiece, they are usually a hindrance to materials process operations which usually result in damaging the tools, increasing energy consumption, the contamination of processed material by wear particles and also some problems associated with technologies to control friction and wear. The most well established method to control friction and wear is by the application of lubricant such as fluorocarbon. Besides, a surface technique so-called surface modification can be applied to solve the tribology problems of the die applications for both the economical and ecological reasons. In this article, we applied DLC(diamond-like carbon) thin film on alumina ceramic for HT test using the PIID(plasma ion immersion deposition), 4 groups of test specimens were tested up to $200^{\circ}C$ which is a little higher than the normal working temperature of die application. Pin-on-disc tribo-tester was used to test the friction and surfaces were characterized by SEM and EDS and else, the morphology changes of DLC coatings were studied. The present work indicated that the DLC had a great potential to reduce the friction and wear in the alumina die application without lubricants.

• 한국기계가공학회지
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• 제2권1호
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• pp.57-62
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• 2003

Machining technique for optical crystals with single point diamond turning tool is reported in tills paper. The main factors influencing 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. SPDT has been widely used in manufacturing optical reflectors of non-ferrous metals such as aluminum and copper which are easy to be machined for their proper ductility. But optical crystals being discussed here are characterized by their high brittleness which makes it difficult to obtain high quality optical surfaces on them. The purpose of our research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle materials. As a result, the cutting force is steady, the cutting force range is 0.05-0.08N. The surface roughness is good when spindle is above 1400rpm, and feed rate is small. The influence of depth of cut is very small.

• 한국기계가공학회지
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• 제14권4호
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• pp.160-166
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• 2015

Ultrasonic machining (USM) has been considered a new, cutting-edge technology that presents no heating or electrochemical effects, with low surface damage and small residual stresses on brittle workpieces. However, nowadays, many researchers are paying careful attention to the disadvantages of USM, such as low productivity and tool wear. On the other hand, in this study, a high-performance rotary ultrasonic drilling (RUD) spindle is designed and assembled. In this system, the core technology is the design of an ultrasonic vibration horn for the spindle using finite element analysis (FEA). The maximum spindle speed of RUM is 9,600 rpm, and the highest harmonic displacement is $5.4{\mu}m$ noted at the frequency of 40 kHz. Through various drilling experiments on glass workpieces using a CVD diamond-coated drill, the cutting force and cracking of the hole entrance and exit side in the glass have been greatly reduced by this system.

• 한국공작기계학회논문집
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• 제15권4호
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• pp.44-48
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• 2006

Recently, demand the ultra precision product which is increasing rapidly is used extensively frontier industry field such as semi-conductor, computer, aerospace, precision machine. Ultra precision processing is the portion that is very needed to NT in the field of mechanical engineering. The latest date, together with radical advancement of electronic and photonics industry, necessity of ultra precision processing is on the increase for the manufacture of various kernel parts those are connected with these industrial fields. Specially, require motion accuracy of high resolution of nm order in stroke of hundreds millimeters according as diameter of processing object great and processing accuracy rises. In this case ,the response speed absolute delay because inertial mass of moving part is very large. Therefore, real time motion error compensation becomes very hardly. In this paper, we used ultra precision cutting unit(UPCU) to cope such problem. a UPCU is designed and tested to obtain sub-micrometer from accuracy in diamond turning of flat surfaces. The thermal growth spindle error is compensated for real time using a UPCU driven by piezoelectric actuator along with a laser encoder displacement sensor.

• 한국공작기계학회논문집
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• 제11권3호
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• pp.86-92
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• 2002

In this study, experiments were carried out to investigate the characteristics of grinding and wear process of diamond wheel far ceramic materials. Normal component of grinding resistance of $Al_2$O$_3$ was less then that of $Si_3 N_4$ and $ZrO_2$. This seems to be the characteristics of ceramic tools on work pieces both of high hardness. For the case of $Si_3 N_4$ and $ZrO_2$, as the mesh number of wheel increases, the surface roughness decreases. For the case of $Al_2 O_3$, the surface roughness does not decreases. Specific binding energy decreases as the material removal rate per unit time increases. For the case of $Si_3 N_4$ and $ZrO_2$, grinding is carried out by abrasive wear processes. For the case of $Al_2 O_3$, grinding is carried out by grain shedding process due to brittle fracture.

• 한국정밀공학회지
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• 제27권2호
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• pp.50-59
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• 2010

In this paper, two kind of free-form progressive addition lenses (PALs) were designed with Zernike polynomial surface and anatomically accurate finite presbyopic schematic eyes which have aspheric cornea, aspheric GRIN crystalline lens, aspheric retina, and Gaussian apodization factor. Geometrical and diffraction MTFs were used for the optimization process in sequence. 5th orders of Zernike polynomials were used for the evaluation of progression zones of the two examples. The target MTF was set as 0.22 at 100 lp/mm which satisfies the standard visual resolution. These examples were fabricated with a CNC diamond turning machine controlled by slow tool servo (STS). After polishing process, the wavefront aberrations were measured with a laser interferometer on the ten test points across the progression zones and then compared with three current commercially available PALs on the optical performance. Astigmatic aberrations of the examples are very lower than the three selected PALs and have more increased stabilized progressive intermediate zones and near zones. It is expected to give better clear and comfortable distance, intermediate and near visions than other conventional PALs and to improve the adaptability of presbyopic patients to PALs.

• International Journal of Precision Engineering and Manufacturing
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• 제4권3호
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• pp.48-54
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• 2003

This paper deals with mirror grinding of a small-sized aspherical lens by a resin bonded diamond spherical wheel. Up to now, a spherical lens has been used for the lens of the optical communication optical part. However, recently, aspherical optical parts are mainly used in order to attempt the improvement in image quality and miniaturization of the optical device. It is possible to manufacture the aspherical lens which is presently being used in optical instrument through ultra-precision machining technology. Also, to realize compactness, efforts are being made to produce a micro aspherical lens, fur which the development of a high-precision, micro molding die is inevitable. Therefore, extensive research is being done on methods of producing a micro aspherical surface by high-precision grinding. In this paper, the spherical wheel was trued by cup-shaped truer and tool path was calculated by the radius of curvature of the wheel after truing and dressing. Then in the aspherical grinding experiment, WC material which is used as a melding die for the small-sized aspherical lens was ground. The results showed that a form accuracy of 0.1918 $\mu\textrm{m}$ P-V and a surface roughness of 0.064 $\mu\textrm{m}$ Rmax could be achieved.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제3회 금형가공 심포지엄
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• pp.249-254
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• 2004

광의 효율적 사용을 위해 표면에 마이크로 그루브가 새겨진 고성능 광학 부품의 개발이 활발하고, 이들 부품의 다량 생산을 위한 초정밀 금형제조기술이 각광을 받고 있다. 최근의 초정밀 미세 기계가공의 경우 간단한 공정으로 이러한 마이크로 그루브 금형을 제작할 수 있다. 특히 조명각 변조용 렌티큘러 렌즈와 같이 실린더형 그루브 금형의 경우에는 기존의 Lithography, MEMS, LIGA 등 광 에너지를 이용한 다른 제조방법들에서는 가공하기 어려운 점이 있으나, 기계가공에서는 쉽게 제작가능한 장점이 있다. 본 연구에서는 이러한 미세기계가공기술의 장점을 활용하여 U 형 마이크로 그루브를 가진 Lenticular 렌즈용 금형을 가공하고자 하였다. 가공에는 3 축 구동의 초정밀 미세 복합가공기와 단결정 천연 다이아몬드공구가 사용되었고, 가공방식은 마이크로 세이핑 공정을 적용하였으며, 가공 금형 재료에는 Brass와 무전해 Nickel이 사용되었다. 실험을 통하여 금형가공시의 절삭력, 칩 형상, 가공표면 등의 분석이 수행되었으며 이를 기반으로 여러 가지 가공문제점을 해결하고, 최종적으로 양호한 렌티큘러렌즈용 금형을 가공하였다.

• 한국생산제조학회지
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• 제18권6호
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• pp.621-628
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• 2009

Because the Ultra-Precision Technology increase its competitiveness in the field of the design, precision of processing technology, confidence and fixation degree are major considerations. According to Pattern shapes using these processing technologies, Light Reflection has influence on the sense of sight about human being. Based on background of these studies, we draw a plan about a round workpiece using a 3D design program and analyze the effect on Light Reflection changing a pattern angle and a source of light through SPEOS program in this research. We make Pattern form as V-Shape, and compare the area distributed by Light Reflection by classifying angle into 4 and analyze changes according to a source of light. In order to measure and evaluate the data from simulation analysis we has manufactured Diamond Tool and has processed Pattern precision using a Ultra-Precision Machine. Based on the result of this study, we forecast that the field of design will achieve rapid growth due to Ultra-Precision Technology in the world market.

• 한국결정학회지
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• 제6권2호
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• pp.88-92
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• 1995

X-선을 이용한 초정밀 측정은 길이, 각도, 결정구조해석 등 많은 분야에서 응용되고 있다. 본 논문은 실리콘 결정을 이용한 초정밀 각도측정에 대한 결과이다. 실리콘 단결정 내부의 여섯 개의 [220] 격자면들은 60°의 사이각(정확도 ∼10-8 rad) 을 이루고 있으므로 육가기둥형의 다면체를 만들어 각도 표준물로 이용하였다. 이러한 각도교정용 실리콘 다면체(silicon polygon)를 사용하여 분해능이 0.36"인 회전엔코더(rotary encoder)의 정확도를 교정하였고, 그 결과를 기존의 회전눈금원판(indexing table)을 사용하여 교정한 결과와 비교하였다.