• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.266-272
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• 2002

High-speed machining is one of the most effective technology to improve productivity. Because of the high speed and hugh fried rate, high-speed machining can alive great advantages for the machining of dies and molds. This paper describes on the improvement of machining accuracy in high-speed machining. Depth of cut, feed rate and spindle revolution are control factors. The effect of the control factors on machining accuracy is discussed fur the results of surface roughness and machining error in Z-direction of the high speed machining.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1052-1058
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• 2003

The possibility of micro/nano machining through electro-chemical process is discussed in this research. Electro-chemical dissolution region is localized within 1 ${\mu}m$ by applying ultra short pulses with tens of nanosecond duration. The effects of voltage, pulse duration, and pulse frequency on the localization distance are investigated. Localization distance can be manipulated by controlling the voltage and pulse duration, and various hole shapes are produced including stepped holes and taper free hole. High quality micro-hole with 8 ${\mu}m$ diameter with 20 ${\mu}m$ depth and micro-groove with 9 ${\mu}m$ width with 10 ${\mu}m$ depth are machined on 304 stainless steel.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.352-357
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• 2001

In this study, residual stress was investigated to evaluate damaged layer in high speed machining through simulation. In machining steel(STDll), residual stress remaining in machined surface was mainly appeared as compressive stress. The scale of this damaged layer more depends on feed per tooth and radial depth than spindle speed. Damaged layer was measured by optical microscope and hardness method. The micro-structure of damaged layer was a martensite because of cutting force and cutting temperature. Thickness of damaged layer is increased with incresing of feed per tooth and radial depth.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1053-1057
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• 1997

Laser thin film process with a Q-switch pulsed YAG laser was performed for micro machining. In this research, we performed basic Cr thin film on glass substrates removal machining experiments. Form experiments, it happens not only evaporration of thin film but also spatter and cohesion of melting substance in working region, when machining a Cr thin film by Q-switch YAG laser beam irradiation. Critical energy of surface irradiation type by irradiation direction of laser in a face composing thin film on the glass is higher than that of back irradiation type, but the latter is favorable because of spatter appearance. In case of image formation position when laser beam is irradiated, the defocus is permitted to a certain extent within forcus depth. Ifexceeds focus depth, formation of pattern is vanishing step by step.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.862-865
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• 2000

The surface grinding of STD-11 was attempted on the machining center. Grinding experiments were performed at the various grinding conditions and the grinding force, machining error, grinding ratio, and surface roughness were measured. The experimental results indicate that the grinding ratio decreases as the table speed and depth of cut increase. The surface roughness of ground surface was not affected by the change of depth of cut. The surface roughness values obtained on the experiments were 0.02 ～ 0.03${\mu}{\textrm}{m}$ which are fairy good and acceptable for ground surface.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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• pp.48-56
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• 2009

In this paper, laser-assisted machining(LAM) has been employed to machine hot isostatically pressed (HIPed) Si3N4 work pieces. Due to little residual flaws and porosity, HIPed $Si_3N_4$ work pieces are more difficult to machine compared to normally sintered $Si_3N_4$ workpieces. In LAM, the intense energy of laser was used to enhance machinability by locally heating the workpiece and thus reducing yield strength. In experiments, the laser power ranges from 200W to 800W and the diameter of work pieces is 16mm. While machining, the surface temperature was kept nearly constant by laser heating except for a short period of rise time of max. 58 seconds. Results showed as feed rate increases the surface temperature of $Si_3N_4$ workpieces decreases slightly, whereas the effect of depth of cut is disregardable. With a laser power of 800W, achievable maximal depth of cut as 0.7mm and feed rate was 0.03mm/rev.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.77-83
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• 2007

The study on damaged layer is necessary for machinability improvement in micro machining. The damaged layer in metal cutting is derived from plastic deformation and transformation of metal structure. The damaged layer affects micro mold life and micro machine parts. In this study, the damaged layer of micro machined surface of copper is evaluated according to various machining condition. The damaged layer structure and metallurgical characteristics are measured by optical microscope, and evaluated by cutting forces and surface roughness. The scale of this damaged layer depends on cutting process parameters and machining environments. By experimental results, depth of damaged layer was increased with increasing of cutting depth, also the damaged layer is less occurred in down-milling compared to up-milling during micro endmilling operation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.393-396
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• 1997

High-speed machining is one of the most effective technologies to improve productivity. Because of the high speed and high feed rate, high-speed machining can give great advantages for the machining of dies and molds. This paper describes on the improvement of machining accuracy in high-speed machining. Depth of cut and feed rate are control factors. The effect of the control factors on machining accuracy is investigated using two-way factorial design.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.88-96
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• 2002

High-speed machining is one of the most effective technologies to improve productivity. Because of the high speed and high feed rate, high-speed machining can give great advantages for the machining of dies and molds. This paper describes on the improvement of machining accuracy in high-speed machining. Depth of cut, feed rate and spindle revolution are control factors. The effect of the control factors on machining accuracy is investigated using two-way factorial design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.245-249
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• 2002

Tungsten carbide microshaft is used as various micro-tools in MEMS because it has high hardness and good rigidity. In this study, experiments were performed to produce tungsten carbide microshaft using electrochemical machining. $H_2SO_4$solution was used as electrolyte because it can dissolve tungsten and cobalt simultaneously. Optimal electrolyte concentration and machining voltage satisfying uniform shape and large MRR of workpiece were found. For one-step machining, the immersion depth over 1 mm was selected for avoidance of concentration of electric charge at the tip of the microshaft. The limit diameter with good straightness was shown and an empirical formula for WC-microshaft machining was suggested. By controlling the various machining parameters, a straight microshaft with 30 $\mu\textrm{m}$ diameter, over 1 mm length and under 0.5$^{\circ}$ taper angle was obtained.