• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.205-206
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• 2007

• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.115-122
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• 2007

Recently, remarkable progress has been made in both technology and production of optical elements including aspheric lens. Especially, requirements for machining glass materials have been increasing in terms of limitation on using environment, flexibility of material selection and surface accuracy. 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 process was developed with an eye to mass production of precision optical glass parts by molding press. This GMP process can produce with precision and good repeatability special form lenses such as camera, video camera, aspheric lens for laser pickup, $f-\theta$ lens for laser printer and prism, and me glass parts including diffraction grating and V-grooved base. GMP process consist a succession of heating, forming, and cooling stage. In this study, as a fundamental study to develop molds for GMP used in fabrication of glass lens, we conducted a glass lens forming simulation. In prior to, to determine flow characteristics and coefficient of friction, a compression test and a compression farming simulation for PBK40, which is a material of glass lens, were conducted. Finally, using flow stress functions and coefficient of friction, a glass lens forming simulation was conducted.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.8
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• pp.60-66
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• 2021

This study aimed at identifying and optimizing the heating-condition parameters that cause surface defects during the compression molding of chalcogenide glass (GeSbSe) lenses through thermal analysis. We derived the optimal heating conditions for molding chalcogenide glass lenses through thermal analysis and analyzed the surface defects. As a result, we observed a significant reduction in surface defects, which verified the analysis process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.525-526
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• 2008

• Elastomers and Composites
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• v.47 no.4
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• pp.341-346
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• 2012

Injection molding is one of the widely used polymer processing operations. It is being used for not only conventional injection molding but gas injection molding, water injection molding, and injection compression molding. Injection compression molding involves injection and compression operation, and it gives uniform physical property and high dimensional quality of product. In this study, injection compression characteristics for various product shapes have been investigated by computer simulation. Product containing side wall showed not much effective in injection compression molding since wall thickness direction was perpendicular to the compression direction. Uniform and low shrinkage was observed in injection compression molding comparing conventional injection molding. Subsequently injection compression molding can be used for molding precise product. Optimal injection compression molding condition was obtained using design of experiment for plastic lens and the results were compared with conventional injection molding.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.143-147
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• 2003

Despite of outstanding optical performance of glass lens, glass lens have not been widely used because of poor productivity and high cost due to manufacturing process i.e. grinding, polishing. However, press-forming method of glass lens overcomes this disadvantage because of mass production. When glass lens is produced by press-forming method using closed die, it is needed that the volume of glass lens preform precisely measured in order to prevent incomplete products and to increase in life of die. The present paper shows the shortcoming of forming process with closed die, and performs FEM simulation of forming process with open die in order to overcome this shortcoming. The design parameter of open die is selected in standard of assembly with optical module and maintenance of optical performance. FEM simulation is carried out with selected parameter of open die and two basic preform. According to distribution of effective strain in glass lens, optical property of glass lens formed at each set of die and preform is compared.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.296-301
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• 2003

Though a glass tens has outstanding optical performance, it has not been widely used because manufacturing process shows poor productivity and high cost. However, press-forming method of glass lens overcomes these disadvantages with mass production. When glass lens is produced by press-forming method using closed die, it is needed that the volume of glass lens preform is precisely measured in order to prevent incomplete products and to increase in life of die. The present. paper shows the shortcoming of forming process with closed die, and performs FEM simulation of forming process with open die in order to overcome this shortcoming. The design parameters of open die are selected on the basis of assembly with optical module and maintenance of optical performance. FEM simulation is carried out with selected parameter of open die and two basic preform. According to distribution of effective strain in glass lens, optical property of glass lens formed at each set of die and preform is compared.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.567-568
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• 2006

Generally, progressive type GMP process is more efficient than batch type because there are advantages that problems of each stage(heating, press, cooling etc.) are easily grasped and a time of production is shortened. But if single cavity is used in progressive type GMP process, there is disadvantage that productivity is decreased. So, in order to improve productivity of progressive type GMP process, it is essential to secure multi cavity mold technic. In this study, as a fundamental study to develop multi cavity used in glass lens molding, we conducted a compression test for PBK40.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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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.