• Tribology and Lubricants
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• 제34권6호
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• pp.209-216
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• 2018

Sapphire is a substrate material that is widely used in optical and electronic devices. However, the processing of sapphire into a substrate takes a long time owing to its high hardness and chemical inertness. In order to process the sapphire ingot into a substrate, ingot growth, multiwire sawing, lapping, and polishing are required. The lap grinding process using pellets is known as one of the ways to improve the efficiency of sapphire substrate processing. The lap grinding process ensures high processing efficiency while utilizing two-body abrasion, unlike the lapping process which utilizes three-body abrasion by particles. However, the lap grinding process has a high material removal rate (MRR), while its weakness is in obtaining the required surface roughness for the final polishing process. In this study, we examine the effects of free abrasives in lap grinding on the material removal characteristics of sapphire substrate. Before conducting the lap grinding experiments, it was confirmed that the addition of free abrasives changed the friction force through the pin-on-disk wear test. The MRR and roughness reduction rate are experimentally studied to verify the effects of free abrasive concentration on deionized water. The addition of free abrasives (colloidal silica) in the lap grinding process can improve surface roughness by three-body abrasion along with two-body abrasion by diamond grits.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1994년도 추계학술대회강연 및 발표대회 강연및 발표논문 초록집
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• pp.9-9
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• 1994

• 한국정밀공학회지
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• 제19권10호
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• pp.195-201
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• 2002

This paper deals with the precision grinding for aspherical surface of optical parts. A parallel grinding method using the spherical wheel was suggested as a new grinding method. In this method, the wheel axis is positioned at a $\pi$/4 from the Z-axis in the direction of the X-axis. An advantage of this grinding method is that the wheel used in grinding achieves its maximum area, reducing wheel wear and improving the accuracy of the ground mirror surface. In addition, a truing by the CG (curve generating) method was proposed. After truing, the shape of spherical wheel transcribed on the carbon is measured by the Form-Talysurf-120L. The error of the form in the spherical wheel which is the value ${\Delta}x$ and $R{^2}{_y}$ inferred from the measured profile data is compensated by the re-truing. Finally, in the aspherical grinding experiment, the WC of the molding die was examined by the parallel grinding method using the resin bonded diamond wheel with a grain size of ＃3000. A form accuracy of 0.16${\mu}m$ P-V and a surface roughness of 0.0067${\mu}m$ Ra have been resulted.

• 한국정밀공학회지
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• 제31권5호
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• pp.367-373
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• 2014

Surface texturing is a machining process on the surface to give engineering functions. The representative process of the surface texturing is lotus effect to give hydrophobic property by the lithography and chemical etching, which is the bio mimic from the nature. Surface texturing can be manufactured by a lot of processes, in particular using mechanical method such as a precise diamond turning, grinding, rolling, embossing, vibrorolling, and abrasive jet machining (AJM). Among them, the grinding process is notable in terms of the wide range of texturing area and fast processing time. The patterning by grinding is done by the grooved grinding wheel on the work piece. In this case, the pattern shape is determined by the grinding conditions as well as the wheel dressing conditions. In this paper, experimental study on the pattern shapes were done and provide the feasibility in use for the large area patterning.

• 한국광학회지
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• 제18권5호
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• pp.362-366
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• 2007

본 연구에서는 3 메가픽셀, 2.5배 줌 카메라폰 모듈용 비구면 유리렌즈 개발을 목적으로 실험계획법(DOE)을 적용하여 성형용 초경 코어의 연삭가공조건을 구하고, 이를 활용하여 비구면 Glass렌즈 성형용 초경합금(WC) 코어를 초정밀 연삭가공을 수행하였다. 또한 가공된 성형용 코어의 가공면 위에 이온증착법으로 다이아몬드상 탄소(Diamond-Like Carbon; DLC) 코팅을 수행하여 DLC 코팅이 성형용 코어의 형상정도(PV)와 표면조도(Ra)에 미치는 영향을 평가하였으며, 비구면 Glass렌즈를 동일한 조건에서 성형하여 성형렌즈의 광학적 특성을 비교하여 성형용 코어면의 DLC 코팅 효과에 대하여 검토하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.199-200
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• 2010

• 한국기계가공학회지
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• 제4권2호
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• pp.10-15
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• 2005

For the development of compensation machining program, ultra precision grinding used in ultra precision machine and corrective machining was studied. We explored a new rough grinding technique on optical material such as zerodur. The facility used is a polishing machine with a custom grinding module and a range of diamond resin bond wheel. Surface roughness and form accuracy are measured by surface measurement equipment(Form Talysurf series2). Our compensation machining program has complied with a target of producing surface roughness better than $0.05{\mu}m$ Ra and form accuracy of around $0.05{\mu}m$ Rt and has been unveiled as a work-hour model.

• 한국공작기계학회논문집
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• 제12권5호
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• pp.40-45
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• 2003

Optical and electronic industries are using lapping and polishing processing as a final finish rather than grinding, because they need more accurate parts of brittles non-metallic materials such as single crystals. Sapphire has been ground by the ultra-precision surface grinder having a glass -ceramic spindle of extremely-low thermal expansion with various cup-type resinoid-bonded diamond wheels of #400-#3000 in grain size. Sapphire can be ground in the ductile mode. And also, the surface roughness and grinding conditions has been clarified. The smooth surface of Sapphire less than 1nm RMS, 1nm Ra can be obtained by the ultra-precision grinding without any polishing process.

• 한국도로학회논문집
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• 제8권3호
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• pp.77-88
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• 2006

현재 도로분야에서 콘크리트 포장의 양적증가와 공용연수 증가로 콘크리트 포장의 손상에 따른 유지보수문제가 크게 부각되기 시작했다. 국내에서 적용되고 있는 콘크리트 포장 유지보수는 통상 손상된 부위의 부분보수후 아스팔트 덧씌우기 공법을 일괄적으로 적용하고 있다. 본 연구에서는 콘크리트 포장의 예방적 유지관리공법인 다이아몬드 그라인딩 공법에 대한 적용기준 평탄성, 미끄럼저항성, 소음, 경제성, 포장의 수명연장등 이론적인 연구를 수행하고, 이를 바탕으로 시험시공을 실시하여 초기공용성에 대한 측정을 실시하였다. 종단평탄성측정은 ARAN의 차륜부 좌우에 별도의 평탄성 측정센서를 부착 자동측정차량을 통해 시공전 후의 평탄성을 측정하였다. 미끄럼저항성은 SN기준값으로 분류하여 다이아몬드 그라인딩 시공전 후의 차로별 미끄럼 저항값을 측정하였다. 소음측정은 시공구간과 일반구간, 차종, 속도를 변수로 선정하여 소음발생정도를 측정하였고, 시공전 후의 평균조도깊이를 측정하여 다이아몬드 그라인딩 공법의 평가를 실시하였다. 분석결과 종단평탄성은 시공후 $6%{\sim}40%$가 향상되었으며, 미끄럼저항성은 1차로에서 66%, 2차로에서 37%의 증진효과가 있었다. 소음은 다이아몬드 그라인딩 구간에서 평균 3.4dB의 소음감소 효과가 나타났으며, 평균조도 깊이는 79%의 깊이 항상 효과를 보였다. 그러므로, 향후 기존 콘크리트 포장의 유지보수공법으로서 다이아몬드 그라인딩 공법의 국내적용이 적정하다고 판단된다.

• 한국정밀공학회지
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• 제12권8호
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• pp.27-38
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• 1995

For solving troubles happened during the drilling process with carbon fiber epoxy composite materials(CFRP) by using HSS drill, a few types of diamond gift electroplated drills are manufactured, and machinability of these drills is experimented with a variety of cutting speed and feed rate. These drills have some advantages of good wear resistant and the conception of grinding process. As a result, using of these drills improves both troubles being caused by tool wear and damage of exit surface depending on fiber stacking angle. It is desirable that cutting conditions for the cutting thickness per revolution must be set under 0.01mm when the size of a diamond grit is # 60 .approx. 80.