• 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.

• Design & Manufacturing
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• 제2권3호
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• pp.16-21
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• 2008

In recent, the demands of household cases and disposable products is increased significantly because a living standard of newly-emerging nations was risen. Therefore, multi-cavity mold and stack mold for the realization of high-productivity have been researched in forefront nations. In this paper, CAE analysis for minimizing the mold core deformation was performed. Finally, 64 cavities injection mold for molding cap which has the insert-type core was fabricated according to the result of CAE analysis.

• 한국전기전자재료학회논문지
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• 제20권9호
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• pp.808-811
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• 2007

Aspheric glass lens have recently been used in camera phone module because they are more effective than spherical ones. In this paper, the grinding condition of the tungsten carbide molding core has been found after applying DOE to the development of the aspheric glass lens for the 3 Megapixel and 2.5x camera-phone module. Also, the ultra precision grinding process was investigated under this condition by experiment. Re-Ir coating was applied on the ground surface of the tungsten carbide molding core. The influence of Re-Ir coating on the form accuracy and surface roughness of molding core was compared and evaluated. The form accuracy and surface roughness of the molding core were improved by application of Re-Ir coating on the surface of the tungsten carbide molding core.

• 한국정밀공학회지
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• 제27권7호
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• pp.117-122
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• 2010

Recently, aspheric glass lens molding core is fabricated with tungsten carbide(WC). If molding core is fabricated with silicon carbide(SiC), SiC coating process, which must be carried out before the Diamond-Like Carbon(DLC) coating can be eliminated and thus, manufacturing time and cost can be reduced. Diamond Like Carbon(DLC) is being researched in various fields because of its high hardness, high elasticity, high durability, and chemical stability and is used extensively in several industrial fields. Especially, the DLC coating of the molding core surface used in the fabrication of a glass lens is an important technical field, which affects the improvement of the demolding performance between the lens and molding core during the molding process and the molding core lifetime. Because SiC is a material of high hardness and high brittleness, it can crack or chip during grinding. It is, however, widely used in many fields because of its superior mechanical properties. In this paper, the grinding condition for silicon carbide(SiC) was developed under the grinding condition of tungsten carbide. A silicon carbide molding core was fabricated under this grinding condition. The measurement results of the SiC molding core were as follows: PV of 0.155 ${\mu}m$(apheric surface) and 0.094 ${\mu}m$(plane surface), Ra of 5.3 nm(aspheric surface) and 5.5 nm(plane surface).

• 한국정밀공학회지
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• 제26권1호
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• pp.51-56
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• 2009

Recently, with the increasing lightness and miniaturization of high resolution camera phones, the demand for aspheric glass lens has increased because plastic and spherical lens are unable to satisfy the required performance. An aspheric glass lens is fabricated by the high temperature and pressure molding using a tungsten carbide molding core, so precision grinding and coating technology for the molding core surface are required. This study investigates the effect of diamond-like carbon (DLC) and rhenium-iridium (Re-Ir) coating For aspheric molding core surface. The grinding conditions of the tungsten carbide molding core were obtained by design of experiments (DOE) for application in the ultra precision grinding process of the tungsten carbide molding core of the aspheric glass lens used in 5 megapixel, $4{\times}$ zoom camera phone modules. A tungsten carbide molding core was fabricated under this grinding condition and coated with the DLC and Re-Ir coating. By measurements, the effect of DLC and Re-Ir coating on the form accuracy and surface roughness of molding coer was evaluated.

• 한국기계가공학회지
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• 제15권6호
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• pp.50-57
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• 2016

Refrigerator glass shelves are manufactured by Insert Injection Molding. The current process of injection of glass into the mold induces movement of the core, on urethane springs. Defects in the product can result from too low a force being transmitted from the springs. To solve this problem, the force on the moving core and the injection molding pressure were subjected to numerical analysis. Based on this, the number of urethane springs as well as their hardness was changed to improve the situation. The number of springs was changed from 6 to 4. The diameter of the springs was increased from ${\emptyset}75$ to ${\emptyset}100$, and the hardness was increased from 70 (shore A) to 90 (shore A). These improvements caused the force on the molding core to increase by approximately 65,442 N. The proportion of defects decreased by 66%.

• 유변학
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• 제11권2호
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• pp.159-167
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• 1999

샌드위치 사출성형 공정은 기존의 사출성형 공정이 가지지 못하는 여러 장점들로 인해 최근 산업적으로 주목 받고 있는 고분자 가공 공정이다. 이 공정의 해석적인 접근은 거의 불가능하므로, 본 연구에서는 수치모사를 통해서 샌드위치 사출성형의 충전 공정을 연구하였다. 수치모사는 기본적으로 유한요소법을 사용하였고 Flow Analysis Network(FAN)/관할체적(Control Volume)법 등을 함께 이용하였다. 그리고 skin polymer의 선단을 확인할 수 있는 기존의 충전율 변수와 함께 skin polymer와 core polymer의 경계를 표시하는 새로운 충전율 변수를 도입하였고 이것을 이용하여 core polymer의 선단을 추적하였다. 새로운 충전율 변수는 두께 방향으로 온도장을 풀기 위해 나눈 각 층에서 정의되었다. 수치모사에 사용된 skin polymer와 core polymer로는 물성이 다른 두 고분자 물질을 주입시켜서 나타나는 충전 형태를 비교했다. 즉, 점도 상수, power-law 지수 등과 같은 유변 물성이 다른 두 고분자 물질을 충전시키기 위해 공정상 필요한 입구에서의 압력 등을 계산했으며 나중에 들어가게 되는 core polymer의 충전 완료 후 금형 내에서의 두께 방향과 흐름 방향으로의 분포 등을 구하였다. 또한 실제 공정 상에서 가공조건에 해당되는 switchover time과 벽 온도 등의 조건을 바꿔가면서 수치모사를 진행하였다. 사례 연구를 통하여 얻어진 물성과 가공 조건에 따른 core polymer의 충전 형태와 입구에서의 압력 등은 샌드위치 사출성형의 산업적 이용에 매우 유용하게 사용될 수 있다.

• Design & Manufacturing
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• 제8권2호
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• pp.7-11
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• 2014

The Core-Shift is often generated on injection mold which have thin and long core. And Core-Shift brings out problems for thickness variation and product ejecting process. In this study, analysis of Core-Shift was performed according to change of materials of core(steel P-20, Be-Cu) and various polymers(PP, PC) by using MoldFolw MPI 6.1 which is commercial injection molding analysis program. As the results of analysis, the magnitude of Core-Shift was increased as being use polymer had lower fluidity and lower rigidity core. In the future, we will study the relationship between amount of Core-Shift and ejecting force.

• 한국정밀공학회지
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• 제26권1호
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• pp.57-62
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• 2009

Recently, with the increasing lightness and miniaturization of high resolution camera phones, the demand for aspheric glass lens has increased because plastic and spherical lens are unable to satisfy the required performance. An aspheric glass lens is fabricated by the high temperature and pressure molding using a tungsten carbide molding core, so precision grinding technology for the molding core surface are required. This paper reports a development of feedrate control grinding method for aspherical molding core using parallel grinding method. A plane molding core was ground using conventional and feedrate control grinding method. The performance of the feedrate control method was evaluated by measurement of surface roughness. The result indicated that the average surface roughness was reduced to 1.5 nm, which is more efficient than the conventional grinding method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.441-441
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• 2007

As Rhenium-Iridium{Re-Ir) coating possesses such features as, high hardness, high elasticity, abrasion resistance and chemical stability, there have been exerted continuous efforts in research works in a variety of fields, and this technology has also been applied widely to industrial areas. In this research, the optimal grinding condition was identified using Microlens Process Machine in order to contribute to the development of aspheric glass lens for mobile phone module having 3 mega pixel and 2.5X zoom, and molding core(WC) was manufactured having performed ultra-precision machining. Effects of Re-Ir coating on form accuracy (P-V) of molding core and surface roughness(Ra) were measured and evaluated.