• 한국공작기계학회논문집
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• 제15권1호
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• pp.108-112
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• 2006

A Study of birefringence in an aspheric lens of injection molding became more important to improve its optical properties. In the present study, the experimental study was carried out to investigate the relationship between birefringence and injection molded conditions. The processing factors are conditions include packing pressure, packing time, injection speed, melt temperature of optical resin and wall temperature. Birefringence was observed figures by using a polarizer in light. This experiments were carried out using the simulation software and injection molding machine.

• 한국공작기계학회논문집
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• 제16권3호
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• pp.117-124
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• 2007

In order to operate CD and DVD compatibly in a pickup system, the objective lens comprise diffractive optical element(DOE) zone and aspheric curvature on its lens surface. The DOE objective lens is effective to simplify this dual-purpose pickup system of the 655nm and 785nm wavelength by using only one lens, but requires more precision manufacturing process and system due to the complicated shape. This paper presents the overall manufacturing process of this objective lens and describes main parameters in each process, for the correction of the aspheric surface in its core, the shrinkage compensation after injection molding, and the uniformity compensation by adjusting molding conditions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.97-98
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• 2013

• 소성∙가공
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• 제24권6호
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• pp.437-442
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• 2015

The development of polishing technology has enabled the production of injection molds with high quality surfaces and shapes. For products such as mobile phones which require high quality performance the use of plastic materials has many constraints such as shrinkage and deflection. The purpose of the current research is to use reverse engineering in order to find and analyze the data of a selected aspherical lens and then creating a process to design an improved lens. Additionally, the improved lenses are subject to molding analysis. In order to solve this problem, the lens construction program, Zemax, was used to analyze and optimize performance. In the case of optimization, the object was to eliminate spherical aberration and to find good MTF data. The result of the optimization data was similar to the MTF data found from a random lens. Specific resin and analysis conditions were selected and CAD modeling was done to enhance the injection molding analysis.

• 대한기계학회논문집A
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• 제39권10호
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• pp.1021-1028
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• 2015

최근 휴대폰용 카메라에 널리 사용되는 초소형 렌즈는 사출성형으로 생산되고 있다. 초소형 렌즈는 제품 크기에 비해 러너부가 상태적으로 큰 비중을 차지하는 특성이 있어 이에 특화된 금형설계 및 성형조건의 설정이 필요하다. 본 연구에서는 초소형 렌즈의 사출성형을 위한 박판형 러너구조를 제안하였다. 제안된 러너구조를 적용한 사출성형 공정의 전산모사를 수행하고, 해석 결과를 기존의 원통형 러너의 결과와 비교하였다. 해석 결과 박판형 러너의 경우 원통형 러너에 비해 냉각시간이 상당부분 절감되나 사출압은 다소 증가됨을 확인하였다. 또한 박판형 러너의 두께를 변화시켜가며 해석을 수행하여 유동특성과 냉각특성의 변화를 종합적으로 고려한 최적의 러너두께를 결정하였다.

• 한국정밀공학회지
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• 제31권11호
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• pp.1031-1040
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• 2014

In this paper, a new condition diagnosis algorithm for the lens injection molding process using various features extracted from cavity pressure, nozzle pressure and screw position signals is developed with the aid of probability neural network (PNN) method. A new feature extraction method is developed for identifying five (5), seven (7) and two (2) critical features from cavity pressure, nozzle pressure and screw position signals, respectively. The node energies extracted from cavity and nozzle pressure signals are also considered based on wavelet packet decomposition (WPD). The PNN method is introduced to build the condition diagnosis model by considering the extracted features and node energies. A series of the lens injection molding experiments are conducted to validate the model, and it is demonstrated that the proposed condition diagnosis model is useful with high diagnosis accuracy.

• 한국정밀공학회지
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• 제32권11호
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• pp.961-968
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• 2015

This study aims to develop an efficient mold structure for the injection molding of a subminiature lens, using shell-type runners instead of traditional cylindrical runners. While the shell runner has the advantage of shorter cooling time due to its thinner geometry, this smaller thickness causes an increase in injection pressure. In this study, the design of the shell runner was modified to contain multiple holes for the purpose of reducing injection pressure. Numerical analyses were performed for shell runners of various hole-shapes, and the resulting filling and cooling characteristics were discussed; the rhombic hole showed the best result for both filling and cooling characteristics. Subsequently, injection molding experiments were performed using an injection mold fabricated based on the rhombic design. The lens parts were successfully molded with highly-reduced cycle time and without degradation of part quality.

• 한국기계가공학회지
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• 제17권1호
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• pp.95-100
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• 2018

This study has focused on the weld-line and birefringence reduction of a plastic optic lens using over and CAE analysis in injection compression molding. A concave lens, which has a thin thickness in the center and a large difference in thickness between the center and the periphery, often causes weld-line defects during injection molding. CAE analysis has been applied to optimize the overflow design in order to reduce the weld-line defects and the polarization defects. To reduce the weld line and birefringence defects, overflow design and application using CAE analysis show that the measured birefringence values of the specimens before the overflow application were 46.8nm and 36.9nm, and the values after the over-flow application were 13.6nm and 14.0nm. From the experimental results, it is confirmed that birefringence is greatly improved when overflow is applied.

• 한국정밀공학회지
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• 제33권1호
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• pp.23-29
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• 2016

In this paper, a real-time condition diagnosis system for the lens injection molding process is developed through the use of LabVIEW. The built-in-sensor (BIS) mold, which has pressure and temperature sensors in their cavities, is used to capture real-time signals. The measured pressure and temperature signals are processed to obtain features such as maximum cavity pressure, holding pressure and maximum temperature by the feature extraction algorithm. Using those features, an injection molding condition diagnosis model is established based on a response surface methodology (RSM). In the real-time system using LabVIEW, the front panels of the data loading and setting, feature extraction and condition diagnosis are realized. The developed system is applied in a real industrial site, and a series of injection molding experiments are conducted. Experimental results show that the average real-time condition diagnosis rate is 96%, and applicability and validity of the developed real-time system are verified.

• 한국융합학회논문지
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• 제6권1호
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• pp.43-48
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• 2015

본 연구는 수술실 무영등용 PMMA 렌즈를 무결함 상태로 사출성형하는 조건을 조사하였다. 렌즈 제작용 수지는 PMMA를 적용하였으며 금형은 자체 제작한 가열-냉각 방식의 금형을 사용하였다. 사출성형 시 금형의 가열온도가 낮을수록 플라스틱 수지의 유동성에 영향을 미쳐 미성형이 발생하거나 웰드 라인, 플로우 마크가 발생하고, 가열온도가 높으면 휨 변형이 발생하였다. 이러한 결함은 냉각시간이 길어짐에 따라 PMMA 수지 결정화에 기인하는 것으로 판단된다. 본 연구를 통해 PMMA 수지로 결함이 없는 렌즈를 성형하는 최적의 조건은 금형 코어의 가열온도는 110[$^{\circ}C$]였으며, 냉각시간은 25[sec]임을 밝혀내어 최적의 가열-냉각 온도 프로파일링을 확립하는 계기를 마련하였다. PMMA소재를 이용한 광학렌즈의 제작은 낮은 생산단가를 구현할 수 있으며 이로 인해 수술실 무영등에 적용된 플라스틱 광학렌즈에 적극 활용될 것으로 기대된다.