• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.539-542
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• 2008

Recently, GMP(Glass Molding Press) process is mainly used to produce aspheric glass lenses. Because glass lens is heated at high temperature above Ty (yielding point) for forming glass, the quality of aspheric glass lens is deteriorated by residual stresses which are generated in a aspheric glass lens after forming. Before this study, as a fundamental study to develop forming conditions for progressive GMP process, compression, strain relaxation and thermal conductivity tests were carried out to obtain the visco-rigid plastic, the visco-elastic and thermal properties of K-PBK40 which is newly developed and applied for precision molding glass material, In this study, using the experimental results we obtained, a glass lens forming simulation in progressive GMP process was carried out and we could forecast the shape of deformed glass lenses and residual stresses contribution in the structure of deformed glass lenses after forming.

• 소성∙가공
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• 제18권8호
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• pp.633-639
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• 2009

Remarkable progress had been made in both technology and production of optical elements including aspheric lens. In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric lenses requiring high accuracy and having complex profile was rather difficult. Against such a background, the high-precision optical GMP process was developed with an eye on mass production of precision optical glass pasts by molding press. This GMP process can produce with precision and good repeatability special form lenses such as for cameras, video cameras, aspheric lenses for optical items. In this study, Design Of Experiment(Taguchi method) was adopted to find a tendency of molding conditions that influence formability. Three main factors for molding conditions were selected based on pressure at pressing stage and temperature, pressure at cooling stage. Also, the DOE was carried out and the interference patterns were measured to evaluate the formability of GMP process. From the results, it was found that the cooling pressure is the most sensitive parameter for progressive GMP process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.354-354
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• 2008

Recently, due to the tremendous growth of media technology, demands of the aspheric glass lens which is a high-performance and miniaturized is gradually increasing. Generally, the aspheric glass lens is manufactured by GMP(Grass Molding Press) method using WC(tungsten carbide) mold core. In this study, the thermal deformation which occurs in the cooling step of GMP was considered, and it was compensated the form of mold core. The lens which was molded by compensated mold core was satisfied that can be applied to the actual specifications.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.289-292
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• 2007

To prevent the damage of glass lens molds and deterioration of glass lenses using in progressive GMP process, a thermal stress and a deformation of the glass lens molds at forming temperature should be considered in the design step. In this study, as a fundamental study to develop a multi cavity mold used in an aspheric glass lens molding, a heat transfer and a thermal stress analysis were carried out for the case of one cavity glass lens mold used in progressive GMP process. Finally, using analysis results, we estimated the thermal stress in a glass lens mold and predicted a modified height of guide ring that determines the forming height of a glass lens.

• 세라미스트
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• 제21권4호
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• pp.427-432
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• 2018

In this study, the aspherical lens for optical communications produced not with an one-step pneumatic type of external pressurization system (existed GMP process) but a constant weight of self-loaded mold put up to upper core. So the lens is molding with self-loaded weight molding and it calls Weight Molding process. In self-loaded molding process, we measured changes of center thickness molding lenses with each variable molding temperatures and time to find the effect of center of lens thickness to search key factors. As experimental results, the center thickness reach to targeted lenses step time value was changed drastically and it depends by molding temperature. If the molding temperature gets higher, the targeted lens that is reaching to the center thickness step time value was decreased. To find the effect of life improvement on mold core by imposing the self-loaded molding process we molded with GMP(Glass molding press) method and self-loaded molding method for 9,000 times and measured the lenses shape accuracy and surface roughness to evaluate the core life. As a result the self-loaded molding method core has 2,000 times longer that GMP (Glass molding press) method. If we adopt self-loaded molding method of the optical aspherical lens molding in the future, we expect that it would reduce the expense of changing the molds by molding core life improvements.

• 한국산학기술학회논문지
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• 제12권3호
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• pp.1051-1057
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• 2011

최근 개발된 GMP공정의 활용으로 디지털 카메라, 광저장기기, 각종 전자기기 등의 광응용 기기에서 비구면 유리렌즈가 폭넓게 활용되고 있다. GMP공정은 복잡한 형상의 유리렌즈를 정밀하면서도 경제적으로 생산할 수 있다. 본 연구에서는 다구치 실험계획법을 이용하여 순차이송형 GMP공정에서 비구면 유리렌즈의 성형 조건을 최적화 하였다. 냉각 1단계에서의 압력과 온도, 시간을 3가지 주요 공정변수로 정하였으며, 3캐비티 금형을 이용하여 실험한 결과 순차이송형 유리렌즈 성형공정에서 냉각시간이 비구면 유리렌즈의 형상정밀도(PV)에 가장 큰 영향을 미치는 것을 알 수 있었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.217-218
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• 2010

• Journal of the Optical Society of Korea
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• 제11권3호
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• pp.85-92
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• 2007

In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric glass lenses requiring high accuracy and having complex profile was rather difficult. In such a background, the high-precision optical glass molding pressing (GMP) process was developed with an eye to mass production of precision optical glass parts by molding press. In this paper, as a fundamental research to develop the multi-cavity mold for higher productivity of a progressive GMP process used in the fabrication of an aspheric glass lens, an aspheric glass lens forming simulation was carried out.

• 한국정밀공학회지
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• 제25권12호
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• pp.125-131
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• 2008

In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric lenses requiring high accuracy and having complex profile was rather difficult. In such a background, the high-precision optical GMP processes were developed with an eye to mass production of precision optical glass parts by molding press. Generally because the forming stage in a GMP process is operated at high temperature above $570^{\circ}C$, thermal stresses and deformations are generated in the aspheric glass lens mold that is used in GMP process. Thermal stresses and deformations have negative influences on the quality of a glass lens and mold, especially the height of the deformed glass lens will be different from the height of designed glass lens. To prevent the problems of a glass lens mold and the glass lens, it is very important that the thermal stresses and deformations of a glass lens mold at high forming temperature are considered at the glass molds design step. In this study as a fundamental study to develop the molds used in an aspheric glass lens fabrication, a heat transfer and a thermal stress analysis were carried out for the case of one cavity glass lens mold used in progressive GMP process. Finally using analysis results, it was predicted the height of thermally deformed guide ring and calculated the height of the guide ring to be modified, $64.5{\mu}m$. This result was referred to design the glass lens molds for GMP process in production field.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.463-464
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• 2009