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        • KCI등재

          Study on Ultra-Precision Grinding Processing for Aspheric Glass Array Lens WC Core

          고명진(Myeong Jin Ko),박순섭(Soon Sub Park) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.11

          Plastic array lens are cheap to manufacture; however, plastic is not resistant to high temperatures and moisture. Optical glass represents a better solution but is a more-expensive alternative. Glass array lens can be produced using lithography or precision-molding techniques. The lithography process is commonly used, for instance, in the semiconductor industry; however, the manufacturing costs are high, the processing time is quite long, and spherical aberration is a problem. To obtain high-order aspherical shapes, mold-core manufacturing is conducted through ultra-precision grinding machining. In this paper, a 4 X 1 mold core was manufactured using an ultra-precision machine with a jig for the injection molding of an aspherical array lens. The machined mold core was measured using the Form TalySurf PGI 2+ contact-stylus profilometer. The measurement data of the mold core are suitable for the design criterion of below 0.5 ㎛.

        • SCIEKCI등재

          Development of an Electronically Controlled Variable Displacement Vane Pump for Engine Lubrication

          Truong, Dinh Quang,Truong, Bui Ngoc Minh,Ahn, Kyoung Kwan,Lee, Jae Shin Korean Society for Precision Engineering 2015 International Journal of Precision Engineering and Vol.16 No.9

          Lubrication is one of the most important factors in developing internal combustion engines. And vane pumps are known as potential choices for conducting the engine lubrication systems. To better optimize the lubrication performance, an electronically controlled variable displacement vane pump developed from a typical vane pump is newly introduced in this paper. Firstly, the concept and methodology to design properly an electric actuator to provide an additionally degree of pump control by regulating the pump displacement is carefully considered. Secondly, a control logic is developed to manage the operation of the actuator and subsequently, smoothly varying the pump output in order to satisfy any given lubrication profile. Finally, test rigs are setup to investigate the performances of the fabricated actuator and pump prototype. Practical tests are performed to evaluate the effectiveness of the newly pump design over the typical one.

        • SCIEKCI등재

          Development and Experimental Performance Validation of Torsional Viscosity Damper for Crank Shaft System of Transporting Machine

          Hong, Do-Kwan,Ahn, Chan-Woo,Shim, Jae-Joon,Lee, Sang-Suk,Jung, Young-Duk Korean Society for Precision Engineering 2015 International Journal of Precision Engineering and Vol.16 No.7

          The purpose of the present study is to deal with the development of a viscosity damper for the crank shaft system of a transporting machine using reverse engineering. A viscosity damper is developed to substitute import product. An engine simulator for performance evaluation has been produced to enable the control of engine speed using a PID controller and to evaluate the performance of several models by reverse engineering. Several prototypes are made according to the mass variation of an inertia ring. To evaluate the reduction effect of torsional vibration by viscosity damper, several sensors are used such as microphone, tri-axis accelerometer and the optical fibre sensor. In addition, order tracking and FFT (Fast Fourier Transform) analysis are performed by FFT analyzer and F/V converter according to speed increase (1,000~4,000 rpm). The viscosity damper for a high performance to reduce torsional vibration has been developed successfully using several designs, structural stability analysis and manufacturing techniques, as well as performance tests.

        • SCIEKCI등재

          Manufacturing and Mechanical Evaluation of Cooled Cooling Air (CCA) Heat Exchanger for Aero Engine

          Kim, Chang-Soo,Kim, Hyeon-Jun,Cho, Jong-Rae,Park, Sang-Hu,Ha, Man-Yeong Korean Society for Precision Engineering 2016 International Journal of Precision Engineering and Vol.17 No.9

          Recent studies on improving the efficiency of gas turbine engines have focused on increasing the inlet temperature of gas flowing into the turbine. For the high inlet temperature, it requires the development of a super-alloy based material that can withstand harsh operating conditions. However, it is essential to utilize alternative solutions such as turbine blade cooling technology. Unfortunately, lightweight, high performance, and high mechanical reliable heat exchangers for aircraft have not yet been examined because of the difficulties associated with design optimization and reliability verification under high temperatures and pressures. The purpose of this study is to develop a manufacturing process for a heat exchanger that can be used in aircraft gas turbine engines. The manufacturing process involved preparing fine tubes through multi-step drawing and annealing processes, and joining these to a tube sheet through brazing. In this work, we reported on the total fabrication processes and mechanical integrity tests of a cooled cooling air (CCA) heat exchanger for the aircraft turbine engine. Through the work, a prototype model of a heat exchanger based on a gas turbine assembly was then developed using each of the individual processes. An X-ray CT test and an endoscopy test were performed to inspect the heat exchanger. The results indicated good manufacturing integrity; thus, the developed heat exchanger can be used for cooling turbine blades.

        • KCI등재

          Detection of Absolute Position for Magneto-Optical Encoder Using Linear Table Compensation

          김슬기(Seul Ki Kim),김형준(Hyeong Jun Kim),이석(Suk Lee),박성현(Sung Hyun Park),이경창(Kyung Chang Lee) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.12

          This paper presents the development of a magneto-optical encoder for higher precision and smaller size. In general, optical encoders can have very high precision based on the position information of the slate, while their sizes tend to be larger due to the presence of complex and large components, such as an optical module. In contrast, magnetic encoders have exactly the opposite characteristics, i.e., small size and low precision. In order to achieve encoder features encompassing the advantages of both optical and magnetic encoders, i.e., high precision and small size, we designed a magneto-optical encoder and developed a method to detect absolute position, by compensating for the error of the hall sensor using the linear table compensation method. The performance of the magneto-optical encoder was evaluated through an experimental testbed.

        • SCIEKCI등재

          Geometrical Compensation of Injection-Molded Thin-Walled Parts in Reverse Engineering

          Kim Yeun Sul,Lee Hi Koan,Huang Jing Chung,Kong Young Sik,Yang Gyun Eui Korean Society for Precision Engineering 2005 International Journal of Precision Engineering and Vol.6 No.2

          A geometric compensation of thin-walled molded parts in reverse engineering is presented. Researches in reverse engineering have focused on the fitting of points to curves and surfaces. However, the reconstructed model is not the geometric model because the molded parts have some dimensional errors in measurements and deformation during molding. Geometric information can give an improved accuracy in reverse engineering. Thus, measurement data must be compensated with geometric information to reconstruct the mathematical model. The functional and geometric concepts of the part can be derived from geometric information. LSM (Least square method) is adopted to determine the geometric information. Also, an example of geometric compensation is given to improve the accuracy of geometric model and to inspect the reconstructed model.

        • SCOPUS

          Free-form Surface Generation from Measuring Points using Laser Scanner

          Park, Jae-Won,Hur, Sugn-Min,Lee, Seok-Hee Korean Society for Precision Engineering 2002 International Journal of the Korean Society of Pre Vol.3 No.4

          With the development of a laser scanner of high precision and increased speed, reverse engineering becomes a key approach to reduce the time for the development of new products. But the modeling process is not so automated enough until now. Modeling in real workshops is usually performed by the experienced operators and it requires a skillful technique to get the resultant surface of high quality and precision. In this paper, a systematic solution is proposed to automate the free-form surface generation from the measured point data. Compatibility is imposed to the measured point data during input curve generation. And the compatibility of cross-sectional curve is also considered for the loft surface generation. The data in each step is produced in IGES file format to make an easy interface to other CAD/CAM software without any further data manipulation.

        • SCIEKCI등재

          Structural Integrity Analysis and Evaluation of Cooled Cooling Air Heat Exchanger for Aero Engine

          Kim, Na-Hyun,Cho, Jong-Rae,Ra, Yong-Jae Korean Society for Precision Engineering 2018 International Journal of Precision Engineering and Vol.19 No.4

          The rise in air traffic demand has led to the escalation of concerns about environmental effects, such as pollution emission. Thus, developing a technology that would reduce environmental problems is more urgent. One of the methods for reducing gas emission is to increase the combustion temperature, which, unfortunately, increases the turbine blade temperature. This problem can be solved by installing a heat exchanger on the engine. However, developing the appropriate heat exchanger that can withstand the severe operating conditions of an aircraft engine is difficult. Thus, a heat exchanger has not yet been installed in an aero engine, but is still being developed. This study aims to assess the structural integrity of the heat exchanger being developed. A finite element (FE) analysis was performed under certain flight operating conditions. The surface temperature was measured during the performance test to verify the thermal boundary conditions. The analysis results were then evaluated according to the fatigue strength of Inconel 625 at <TEX>$10^4$</TEX> cycles. Moreover, a transient analysis was conducted to identify the analysis results under a steady state. Its results were compared with those of a static analysis. The comparison showed an acceptable result in their differences. Therefore, the static analysis results of the full model are considered reasonable.

        • SCOPUSKCI등재

          A Study on the Optimum Design of the Spindle Taper Angle by Chucking Force of a 2-Head Simultaneous Grinding Machine

          이춘만(Choon-Man Lee),이정학(Jeong-Hak Lee),정호인(Ho-In Jeong),이정훈(Jeong-Hun Lee) Korean Society for Precision Engineering 2021 한국정밀공학회지 Vol.38 No.2

          In recent years, the machine industry has demanded high precision of the processed products and high efficiency of production due to the rapid development of technology. The grinding machine is being studied in many countries. The typical grinding machine is processed in the order of one side each. However, a 2-head simultaneous grinding machine processes both sides at the same time. Therefore, it has reduced processing time and improved precision. In this study, the overall structural analysis of a 2-head simultaneous grinding machine with high precision and high efficiency of productivity was performed. For high precision of the 2-head simultaneous grinding machine, the spindle taper angle was analyzed and optimized. When the spindle taper angle was 16 degrees, it had the highest chucking force. Therefore, the spindle had high precision as the spindle taper had the strongest force to chuck the collet. The analysis results can be applied to further develop the 2-head simultaneous grinding machine.

        • KCI등재

          비구면 유리렌즈 성형용 SiC 코어의 DLC 코팅에 관한 연구

          박순섭(Soon Sub Park),원종호(Jong Ho Won) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.12

          Technical demands for aspheric glass lens formed in market increases its application from simple camera lens module to fiber optics connection module in optical engineering. WC is often used as a metal core of the aspheric glass lens, but the long life time is issued because it fabricated in high temperature and high pressure environment. High hard thin film coating of lens core increases the core life time critically. Diamond Like Carbon(DLC) thin film coating shows very high hardness and low surface roughness, i.e. low friction between a glass lens and a metal core, and thus draw interests from an optical manufacturing industry. In addition, DLC thin film coating can removed by etching process and deposit the film again, which makes the core renewable. In this study, DLC films were deposited on the SiC ceramic core. The process variable in FVA(Filtered Vacuum Arc) method was the substrate bias-voltage. Deposited thin film was evaluated by raman spectroscopy, AFM and nano indenter and measured its crystal structure, surface roughness, and hardness. After applying optimum thin film condition, the life time and crystal structure transition of DLC thin film was monitored.

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