• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.647-648
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• 2011

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.922-925
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• 2002

Klystron which is micro wave amplifier tube are mainly used in fields of science such as accelerator, nuclear fusion, broadcasting, communication fields, and defense industry fields, tract. The quality of Klystron anode and cavity are determined by form accuracy and roughness of the worked surface. Therefore anode and cavity are restricted the from accuracy strictly and the surface roughness be under Rmax 0.03S. As a work material of anode and cavity, the oxygen-free copper, that is used for optical pares of aerospace and laser mirror is selected. An outside diameter of material is $\Phi$100 mm and an inside diameter is $\Phi$30~33 mm. In this study, to find the optimum ultra precision cuffing condition of oxygen-free copper with diamond turning machine, the surface roughness is examined for various diamond toot nose radius, main spindle speed, fred rate and depth of cut. As a result of experiment, we could machined the anode and cavity with a surface roughness within Ra 3.2 nm, a form accuracy within 0.01 $\mu\textrm{m}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1597-1600
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• 2005

Recently, the trends of TFT-LCD are large scale and thin thickness, so, the demands of Light Guide Panel(LGP) which is able to substitute for prism sheets are appeared. Functions of LGP obtaining polarization of light of the prism sheet as well as the incidence and reflection of light are demanded. This prismless type LGP to complete functions of the existing LGP and polarization at once must be supported by micro machining technology of LGP surface. In this research, we have used the STAMPER method for the mass product and In-Line process, and the optimized conditions are established by analyzing the cutting force and conditions according to the material and processing properties when the prismless type LGP mold is fabricated. Parameters of the cutting condition were the workpiece and cutting depth.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.4
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• pp.9-16
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• 2003

In this study, the decision of dressing time for diamond wheel was analyzed by observing with acoustic emission signals and surface roughness, and also obtained the machining characteristics by weibull distribution plot for the values of bending strength. From the experimental study, it was possible to predict the time of re-dressing for the diamond grinding wheel with the analysis of acoustic emission signals and surface roughness values, and following conclusions were obtained. The root-mem-square values of acoustic emission signals were obtained low as the increased of table speed for different abrasive grain size. This is caused by the lack of grinding power which is not able to get rid of all real grinding mass of depth as the table speed is increased. The values of bending strength for ground $Si_3 N_4$ specimens were decreased for gain size of #400 than that of #60, but it was found that the surface roughness values for gain size of #60 were better than that of #400. As compared the shape parameter of weibull distribution plot for the values of bending strength, it was found that the reliability of bending strength for grain size of #60 increased than that of #400.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.11
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• pp.905-910
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• 2016

Infrared (IR) optic lens can be fabricated by a single point diamond turning (SPDT) machine without subsequent polishing process. However, this machining process often leaves micro-cracks that deteriorate the surface quality. In this work, we propose an experimental design to remove micro-cracks on IR lens. The proposed design gathered data between cutting process condition and Rt surface roughness. This is of great importance because the scale of micro-cracks is a few micrometer. Rt surface roughness is suitable for analyzing maximum peak height signals of the profile. The experimental results indicate that feed per revolution variable is one of the most dominant variable, affecting the generation micro-cracks on IR lens surfaces.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.6
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• pp.52-58
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• 1996

This paper described on the effect of residual stocks in internal grinding of tungsten carbide materials in order to improve the grinding efficiency as well as grinding accuracy. Through the fundamental investigation is carried out for tungsten carbide materials using electroplated diamond wheel, the residual stock after grinding process is effective to the grinding efficiency. The obtained results are as follows: (1) Under the depth of cut(t) is constant and decreasing the workpiece velocity(Vw), the residual stock after grinding is increased, but the difference is little less than the difference by table speed. (2) Increasing the wheel velocity, the residual stock after grinding is decreased. Therefore in order to minimize the residual stock, the wheel velocity should be increased as far as possible. (3) The surface roughness and out-of roundness increased with depth of cut and table speed, and decreased with wheel velocity, but it may as well adopt as much as possible under the dimensional tolerance which is required for high efficiency grinding. (4) In order to remove residual stock, the spark-out grinding shoule be done, and it also can be improved about 20~25% throughout spark-out grinding, and the number of optimal spark-out times were within 10 times.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.183-189
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• 2013

The chalcogenide glass has superior optical properties in IR region transmittances. We have determined the composition of GeSbSe chalcogenide glass for the application of good IR lenses, resulting in the composite rate of $Ge_{19}Sb_{23}Se_{58}$. The optical, structural, thermal and physical properties were measured by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Differential scanning calorimeter (DSC), X-ray computed tomography (X-ray CT) respectively. The fabrication of the chalcogenide glass lens for infrared optics applications was proposed using a diamond turning machining technology which is known as the suitable ways for the production cost reduction and the accurate fabrication process control.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.58-63
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• 2009

Silicon carbide (SiC) has been used for many engineering applications because of their high strength at high temperatures and high resistances to chemical degradation. SiC is very useful especially for a glass lens mold whose components demanded to the machining with good surface finish and low surface damage. The performance and reliability of optical components are strongly influenced by the surface damage of SiC during grinding process. Therefore, the severe process condition optimization shall be necessary for the highly qualified SiC glass lens mold. Usually the major form of damage in grinding of SiC is a crack occurs at surface and subsurface. The energy introduced in the layers close to the surface leads to the formation of these cracks. The experimental studies have been carried out to get optimum conditions for grinding of silicon carbide. To get the required qualified surface finish in grinding of SiC, the selection of type of the wheel is also important. Grinding processes of sintered SiC work-pieces is carried out with varying wheel type, depth of cut and feed using diamond wheel. The machining result of the surface roughness and the number of flaws, have been analyzed by use of surface profilers and SEM.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.1
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• pp.57-62
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• 2003

Machining technique for optical crystals with single point diamond turning tool is reported in tills paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. SPDT has been widely used in manufacturing optical reflectors of non-ferrous metals such as aluminum and copper which are easy to be machined for their proper ductility. But optical crystals being discussed here are characterized by their high brittleness which makes it difficult to obtain high quality optical surfaces on them. The purpose of our research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle materials. As a result, the cutting force is steady, the cutting force range is 0.05-0.08N. The surface roughness is good when spindle is above 1400rpm, and feed rate is small. The influence of depth of cut is very small.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.382-385
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• 2011

There is an immense need to obtain nanometric surface finish on optical glass owing to the advantage of improved performance of the components. But owing to brittleness and hardness, optical glass is one of the materials that is difficult to ultra-precision turning. According to the hypothesis of ductile mode machining, regardless of their hardness and brittleness, will undergo a transition from brittle to ductile machining region below a critical undeformed chip thickness. Below this threshold, it is suggested that the energy required for plastic formation. Thus, plastic deformation is the predominant mechanism of material removal in machining these materials in this mode. An experimental study is conducted diamond cutting for machining BK7 glass. The investigation presents the feasibility of achieving nanometric surface and the understanding the mechanism of cutting glass, proving the cutting edge radius effect.