• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1053-1059
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• 2002

The purpose of this study is to suggest how the machining technique of constant control of cutting speed can improve precision machining and tool life in high speed machining using a ball end mill. Cutting speed is changed in machining fee form surfaces such as connecting rod die. So, we don't have supreme surface form and tool life on machining. To solve this problem we should settle on optimal cutting speeds in free form surface machining. And, to improve precision machining, We must execute high speed machining methods to output optimum NC data using developed constant control of cutting speed program after modeling by CAD/CAM. In this paper, a comparison was made of the cutting precision and tool life in conventional cutting and those in connecting rod machining applying the program developed.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.3
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• pp.201-208
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• 2002

The machine tool which operates by hand is replacing by CNC machine tool to improve the quality of the product and the productivity in modem mechanic industry. The precision of machine part is influenced greatly the surface roughness by cutting condition of machine tool. So this study was performed to examine the aluminium surface roughness of section according to change of strength rating, nose radius, cutting speed, using live center. The results of this study are as follows; 1. In the case of 56mm diameter of test piece(length is below triple of diameter), whether establish the live center or not, doesn't influence to the surface roughness, and it is possible to make product without the live center. 2. The average surface roughness of 42mm diameter(length is quadruple of diameter) is similar to the 56mm diameter in the cutting condition of nose radius 0.8mm and cutting speed 140mm/min, but there are increases and differences in other cutting conditions. 3. In the case of test piece length more 70m/min(140m/mm) and nose radius improved greatly using the live center. 4. In the case of test piece length is quintuple of diameter, the nose radius must choose big tool and increase the cutting speed in preference live center establishment availability to improve that is surface roughness. Conclusively, if aluminum test piece length is fewer than triple of diameter, can process without establishing live center. If aluminum test piece length is more than quintuple of diameter, cutting conditions to improve surface roughness are (1) cutting speed (2) nose radius (3) whether the live center uses or not.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.816-824
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• 2003

In this study, variations of cutting performance with pulse time, open circuit voltage, wire speed and dielectric fluid pressure were experimentally investigated in Wire Electrical Discharge Machining (WEDM) process. Brass wire with 0.25 mm diameter and AISI 4140 steel with 10 mm thickness were used as tool and work materials in the experiments. The cutting performance outputs considered in this study were surface roughness and cutting speed. It is found experimentally that increasing pulse time, open circuit voltage, wire speed and dielectric fluid pressure increase the surface roughness and cutting speed. The variation of cutting speed and surface roughness with cutting parameters is modeled by using a regression analysis method. Then, for WEDM with multi-cutting performance outputs, an optimization work is performed using this mathematical models. In addition, the importance of the cutting parameters on the cutting performance outputs is determined by using the variance analysis (ANOVA).

• KSTLE International Journal
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• v.2 no.2
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• pp.103-113
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• 2001

The influence of aerated oil on high-speed journal bearing is examined by classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The live oil surface tension is considered as functions of temperature, API gravity and air volume ratio. With changing eccentricity ratio, it is investigated the effects of air bubbles on the performance of a high-speed plain journal bearing. Just at the moderate eccentricity ratios, even if the involved aeration levels are not so severe and the entrained air bubble sizes are not so small, it is found that the bearing load and friction farce may be changed so visibly for the high speed bearing operation.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.48-68
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• 2000

The high-speed machining technology of difficult-to-cut material is needed to achieve the high-efficiency of die manufacturing. The high-speed machining is applied in automobile, airplane and electricityㆍelectro industry etc, because it can improve machining efficiency and productivity with high speed, high power and high rotation. In this study, high speed machinability, tool wear characteristics and its monitoring, characteristics of damaged layer, machinability of difficult-to-cut material, characteristics of a free curved surface and method of CAD/CAM system were introduced to acquire the shortening of machining time, the improvement of machining efficiency and the high quality of machined surface. Therefore, we establish the stabilization condition of difficult-to-cut material machining and present the optimal cutting condition for high-efficiency cutting.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.878-881
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• 2000

Recently high speed machining is being studied actively to reduce machining time and to improve machining precision. To perform efficient high speed machining, evaluation of high speed machinability must be studied preferentially and it can be identified by investigation of cutting force, tool wear and surface roughness. In this study. the cutting force and tool wear and surface roughness are investigated in case of various cutting conditions for hardened die steel.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.1
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• pp.1-6
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• 2012

In this paper, an adaptive fuzzy control system is proposed for the speed control of the ASV (Autonomous Surface Vehicle) with nonaffine nonlinear system dynamics. We consider the turning speed of the screw propeller to be the control input instead of thrust so that we do not have to know the exact function between turning speed and thrust. But in this case, the ASV becomes a nonaffine nonlinear system because thrust is a nonlinear function of the turning speed. To solve this problem, we propose a Takagi-Sugeno fuzzy-model-based control system and simulation studies are performed. Simulation results show the effectiveness of the proposed control scheme.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1681-1688
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• 2000

A dynamic model for the prediction of surface topography in high speed end milling process is developed. In this model the effect of tool runout, tool deflection and spindle vibration were taken in to account. An equivalent diameter of end mill is obtained by finite element method and tool deflection experiment. A modal parameter of machine tool is extracted by using frequency response function. The tool deflection, spindle vibration chip thickness and cutting force were calculated in dynamic cutting condition. The tooth pass is calculated at the current angular position for each point of contact between the tool and the workpiece. The new dynamic model for surface predition are compared with several investigated model. It is shown that new dynamic model is more effective to predict surface topography than other suggested models. In high speed end milling, the tool vibration has more effect on surface topography than the tool deflection.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1995.03a
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• pp.1-8
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• 1995

This paper proposed a simple method for measuring surface roughness of ground surface. utilizing non-contact in-process measuring system using the diode laser. The measurement system is consisted of a laser unit with a diode laser and a cylindrical lens a detecting unit with polygon mirror and CCD array sensor. and a signal processing unit with a computer and device. During operation, this measuring system can provide information on surface roughness in the measuring distance with a single sampling and simultanilusly monitor the state of the grind wheel. The experimental results, showed that the increase of the feed rate and the dressing speed an caused increase in the surface roughness and when the surface roughness is 4Rmax-10Rmax, the cutting speed is 1653m/min-1665m/min. the feed rate is 0.2m/min-0.9m/min, the dressing speed is 0.2mm/rev-0.4mm/rev, the stylus method and the in-process method can be obtained the same results. thus under limited working conditions. using the proposed system. the surface roughness of the ground surface during cylindrical grinding can be obtained through the in-process measurement method using the diode laser.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.392-392
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• 2010

In this study, high-speed chemical dry thinning process of Si wafer and evolution of surface roughness were investigated. Direct injection of NO gas into the reactor during the supply of F radicals from $NF_3$ remote plasmas was very effective in increasing the Si thinning rate due to the NO-induced enhancement of surface reaction but thinned Si surface became roughened significantly. Addition of Ar gas, together with NO gas, decreased root mean square (RMS) surface roughness of thinned Si wafer significantly. The process regime for the thinning rate enhancement with reduced surface roughness was extended at higher Ar gas flow rate. Si wafer thinning rate as high as $22.8\;{\mu}m/min$ and root-mean-squared (RMS) surface roughness as small as 0.75 nm could be obtained. It is expected that high-speed chemical dry thinning process has possibility of application to ultra-thin Si wafer thinning with no mechanical damage.