• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.237-238
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• 2006

Micro drilling is a very important machining method to produce precise parts or small molds. General macro-program for drilling is a non-efficient method because of many movements to safety height. In this research new macro-program was suggested to raise machining-efficiency. New micro-drilling method caused the much reduction of machining time and the same tool life.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1995.03a
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• pp.40-62
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• 1995

A micro positioning system using piezoelectric actuators have very wide application region such as ultra-precision machine tool optical device measurement system. In order to keep a high precision displacement resolution it to useful to take a position sensor and feedback of the error. From the practical point of view high-resolution displacement sensor systems are very expensive and it is difficult to make such a sensitive sensor work properly in a poor operational environment of industry. In this study a piezo-electric micro-depth control system which does not require position sensor but piezoelectric voltage feedback has been developed. It is driven by hysteresis-considering reference input voltage calculated in advance and actuator/sensor characteristics of piezoelectric materials. From the result of experiments a fast and stable response of micro-depth control system has been achieved and an efficient technique to control the piezoelectric actuator suggested.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.8-13
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• 2000

In this paper, a new adaptive cross-coupling control (CCC) method with an improved contour error model is proposed to maintain contouring precision in high-speed nonlinear contour machining. The proposed method utilizes variable controller gains based on the instantaneous curvature of a contour and the feedrate command. In addition, a real-time federate adaptation scheme is included in the proposed CCC to regulate cutting force. The proposed method is evaluated and compared with the conventional CCC for nonlinear contouring motion through computer simulations. The simulation results show that the proposed CCC improves the contouring accuracy and regulates cutting force more effectively than the existing method.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.3
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• pp.141-149
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• 1998

Diamond shaping is one of the machining strategies to make the optical micro-groove molds, and it is especially useful when the component is an assembly of the linear micro-groove array. A mirrorlike surface and an arbitrary crose-sectional curve can be easily made by the diamond tool. However, the cutting speed of shaping is relatively lower than that of the other cutting methods, and there exist an unstable cutting conditions that generate the chatter. This study is focused on the modeling of the simplified self-induced chatter of the diamond shaping, and the machinabilities of three materials are compared by cutting experiments. From the chatter model and experiments, it is found that the unstable cutting conditions exist when the depth of cut is low and cutting speed is high. It is also found that the brass is relatively good material in micro shaping than copper or aluminium from the cutting experiments.

• Journal of the Korean Society of Industry Convergence
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• v.16 no.4
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• pp.119-125
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• 2013

To enhance the cutting performance of high speed steel(HSS) endmill, single and multilayer coating is applied on the substrated of the HSS endmill. Coating material reduces cutting force and enhances resistance against abrasive wear. This paper presents the physical vapour deposition(PVD) coating technology and evaluate the PVD coated HSS endmill. The performance of coated HSS endmills are fifteen times better than uncoated HSS endmill on proposed cutting conditions. The TiAlN monolayer coated endmills(futura nano coating) are better than those of multilayer coated endmills(futura coating) on machined surface and tool wear.

• Design & Manufacturing
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• v.2 no.2
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• pp.1-5
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• 2008

Mechanical properties of the materials used for mold and industrial machinery under high strain rate loading conditions such as high impact loading are required to provide appropriate safety assessment to varying dynamically loaded mechanical structures. The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, the dynamic deformation behavior of a brass under high strain rate compressive loading conditions has been determined using the SHPB technique.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2006.06a
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• pp.35-40
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• 2006

Laser welding is high power density welding method which is higher speed and productivity, lower thermal deformation, without material restrictions for car body welding. But, in case of zinc coated sheet metal welding, the gap is needed $0.1{\sim}0.2mm$ to avoid weld bead blowup. This paper describe that it used dimple and pressure roller tool to improve laser welding quality for 3-layer zinc coated sheet metal.

• Korean Journal of Computational Design and Engineering
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• v.8 no.3
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• pp.150-156
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• 2003

Direct Metal Deposition (DMD) is a new additive process producing three-dimensional metal components or tools directly from CAD data, which aims to take mold making and metalworking in an entirely new direction. It is the blending of five common technologies: lasers, CAD, CAM, sensors and materials. In the resulting process, alternatively called laser cladding, an industrial laser is used to locally heat a spot on a tool-steel work piece or platform, forming a molten pool of metal. A small stream of powdered tool-steel metal is then injected into the metal pool to increase the size of the molten pool. By moving the laser beam back and forth, under CNC control, and tracing out a pattern determined by a computerized CAD design, the solid metal part is eventually built line-by-line, one layer at a time. DMD produces improved material properties in less time and at a lower cost than is possible with traditional fabrication technologies.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.877-878
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• 2006

The sintered parts are mainly used for automobile industry, and a part of air conditioners. In automobile industry, the application range of sintered parts is very broad and use for a driving and a lubricating system. And air conditioner uses them for compressor. Grinding of compressor and pump parts is very difficult these days, because these parts use High hardness materials and require high precision grinding. Tool life has to be extended to decrease production cost. We analyzed processing mechanism and developed new grinding wheels for Double Disk Grinding. And, we introduce new truing technology that improved tool-life and precision.

• Journal of the Korea Safety Management & Science
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• v.3 no.1
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• pp.117-125
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• 2001

Polyacetal resin is usually used to make molds, but it is difficult to achieve dimension accuracy during molding. Therefore it is usually necessary to cut the polyacetal resin after a molding process. Polyacetal resin is easily machining by standard machine tool. Acetal is also a thermal stable material which can be totted without coolant Another concern about the use of polyacetal resin is that it absorbs water easily, which also results in problems with dimension accuracy Therefore, in this study, the cutting resistance of water-absorbed polyacetal resin and its surface roughness after cutting in order to achieve the highest degree of accuracy in the cutting of polyacetal resin were investigated. Also, The Robust Design method uses a mathematical tool called orthogonal arrays to study a large number of decision variables with a small number of experiments. It also uses a new measure of quality, called signal-to-noise (S/N) ratio, to predict the quality from the customer's perspective. Thus, we have taken Taguchi's parameter design approach, specifically orthogonal array, and determined the optimal levels of the selected variables through analysis of the experimental results using S/N ratio.