• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.769-772
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• 2005

Five DOF motion errors of a hydrostatic bearing table driven by the coreless type linear motor were compensated utilizing the active controlled capillaries in this study. Horizontal linear motion and yaw error were simultaneously compensated using two active controlled capillaries and vertical linear motion, pitch and yaw error were also simultaneously compensated using three active controlled capillaries. By the compensation, horizontal linear motion accuracy and yaw were improved from 0.16 ${\mu}m$ and 1.96 arcsec to 0.02 ${\mu}m$ and 0.03 arcsec. Vertical linear motion accuracy, pitch and roll were also largely improved from 0.18 ${\mu}m$, 2.26 arcsec and 0.14 arcsec upto 0.03 ${\mu}m$, 0.07 arcsec and 0.02 arcsec. The compensated motion errors were within the range of measuring repeatability which was ${\pm}0.02\;{\mu}m$ in the linear motion and ${\pm}0.05$ arcsec in the angular motion. From these results, it is found that the motion error compensation method utilizing the active controlled capillaries are very effective to improve the five motion accuracies of the hydrostatic bearing tables.

• Tribology and Lubricants
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• v.7 no.1
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• pp.35-39
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• 1991

The performance of the ultra-precision machine tools depends on the steady state characteristics of the main spindle bearings. For excluding the effect of machining error with perpendicularity, conical or spherical bearing has been used. In this paper, steady analysis of the externally pressurized conical gas bearing for ultraprecision is carried out based on the direct numerical method with assumption of point source. As a result of theoretical analysis, design parameters for optimal condition of conical gas bearing are' presented in dimensionless form.

• Tribology and Lubricants
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• v.15 no.3
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• pp.257-264
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• 1999

Recently as electronics and semi-conductor industry develop, ultra-precision machine tools that use air-spindle with externally pressurized air bearing appear in need of ultra-precision products which demand high precision property. Effects of air compressibility absorbs the vibration of shaft, this is called averaging effect, however, the higher running accuracy is demanded by degrees, the more important factor is machining errors that affect running accuracy of shaft. Actually, it would be very important in the view points of running accuracy to understand effects of machining errors on the running accuracy of the spindle system quantitatively to design and manufacture precision spindle system in the aspect that efficiency in manufacturing spindle system and performance in operation. So fu, there are some researches on the effects that machining error affect running accuracy. However, because these researches deal with one bearing of spindle system, these results aren't enough to explain how much machining errors affect running accuracy in the typical spindle system overall. In this study, we investigate the effects of the perpendicularity error of bearing and shaft on running accuracy of spindle system that consists of journal and thrust bearing theoretically, and suggest design guideline about shape tolerances.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.977-980
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• 1997

Ultraprecision machining process and MEMS technology have been taken more and more important position in machining of micro parts such as PDP and IT components, as the application field of micro parts increases. A micro machining center is very effective equipment for the fabrication of micro parts, because of its benefits such as lower power consumption, high precision and lower machining cost. Therefore, we study the possibility of application to the micro machining of barrier ribs used in PDP and also analyse the machining characteristics. The fabricated barrier rib has 30~$200\mu\textrm{m}$ pitch and was made by the flat endmill with the diameter of 0.2mm, 40, 000rpm condition.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.783-786
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• 2000

For the development of a ultra-precision CMC polishing system including on-machine measurement system, we study a corrective polishing algorithm. We calculated unit removal profiles for various polishing tools and polishing tool positions. Using these results we simulate the corrective polishing process based on dwell time control. We calculate dwell time distributions and residual error of the polishing simulation method and the FFT calculation method. We got good dwell time distributions and small residual when we used the FFT calculation method. This results will be used for the optimization of corrective polishing process.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.99-106
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• 2002

For the development of a ultra-precision CNC polishing system including on-machine measurement system, we study a corrective polishing algorithm. We calculated unit removal profiles for various flat type polishing tools and polishing tool positions. Using these results we simulate the corrective polishing process based on dwell time control. We calculate dwell time distributions and residual error of the polishing simulation method and the FFT calculation method. We test corrective polishing algorithm with an optical glass. The target removal shape is a sine wave that has amplitude 0.3 micro meters. We find this polishing process has a machining resolution of nanometer order and is effective for sub-micrometer order machining. This result will be used for the software development of the CNC polishing system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.2
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• pp.199-206
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• 2016

Linear motion (LM) ball guides with rolling contact are core units of feed-drive systems. They are widely applied for precision machinery such as machine tools, semiconductor fabrication machines and robots. However, the friction force induced from LM ball guides generates heat, which deteriorates positioning accuracy and incurs changes of stiffness and preload. To accurately analyze the effects and apply the results to precision machine design, mathematical modeling of the friction force is required. In this paper, accurate formulation of the friction force due to rolling, viscous, and slip frictions is conducted for LM ball guides. To verify the reliability of the developed friction model, experiments are performed under various assembly, load and velocity conditions. Effects of frictional components are analyzed through the formulated friction model.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.76-81
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• 2012

The continuing demand for increasingly slimmer and brighter liquid crystal display(LCD) panels has led to an increased focus on the role of the light guide panels(LGPs) or optical films that are used to obtain diffuse, uniform light from the backlight unit(BLU). And the most basic process in the production of such BLU components is the micromachining. LCD BLUs comprise various optical elements such as a LGP, diffuser sheet, prism sheet, and protector sheet with micro patterns. High aspect ratio patterns are required to reduce the number of sheets and enhance light efficiency, but there is a limit to the aspect ratio achievable for a given material and cutting tool. Therefore, this study comprised a series of experimental evaluations conducted to determine the machining feasibility in microcutting various aspect ratio patterns on electroless nickel plated die materials when using single-crystal diamond tools. Cutting performance was evaluated at various cutting speeds and depths of cut using different machining methods and machine tools.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.31-38
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• 2001

This paper deals with the micro turning property of setting angle using diamond tool. The bed of the system has used the granite which has the thermal and vibrational characteristics superior to the cast iron bed for the common machine tool. To minimize the inner and outer vibration of the fuming system, an air pad system was manufactured and tested. The aero-static spindle system which has the excellent rotation accuracy was designed and manufactured. As a result of the micro-cutting test on aluminum alloy, tool setting angel have effected on surface roughness. From the results, the micro-cutting conditions hope to provide the useful actual data using in industrial fields.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.59-64
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• 2002

One of the exciting research areas of the X-ray microscope is the observation of a living cell. In order to study a living cell with high resolution the order of the several tens nm, we need to improve the efficiency of mirrors which are components of an X-ray microscope system. In this paper we present the mirror design and manufacture to give a high resolution and reflectivity. We designed Wolter type I the condenser and objective mirror with the several tens of nm resolution. According to mirror design. we made the program using the visual basic. Using the new processing method as well as the ultra-precision diamond cutting, we directly processed the inside of an aluminum hulk in order to manufacture mirrors. From the experimental result, we think that the new processing method will improve a high reflectivity through the improved cutting tools and optimum cutting conditions.