• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.30-35
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• 1997

CNC Grinding Center is developed to improve the flexibility of grinding process and to obtain the high machine accuracy in grinding processes. It consists of a built-in type spindle with max. 25,000 rpm, ATC(automatic tool changer) for quick and reliable loading/unloading of tools, a rotary dresser for trueing, dressing, and personal computer based CNC controller, etc. This research concentrates on the machine structure, the evaluation of efficiency, and the machining technology of the developed prototype

• 한국정밀공학회지
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• 제15권8호
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• pp.81-87
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• 1998

High-speed machining is one of the most effective technologies to improve productivity. Because of the high speed and high feedrate, high-speed machining can give great advantages for the machining of dies and molds. In this paper, high-speed machining for HP-4 die material was carried out with a coated tungsten carbide ball endmill. In the high-speed machining, the cutting force and surface roughness of workpiece show various characteristics in different cutting conditions. Especially, the surface roughness of the workpiece depends largely on pick feed and feed-per-revolution of the ball endmill. In the condition where pick feed and feed-per-revolution are equal, better surface roughness is measured. By obtaining good surface roughness at high speed, efficiency of machining can be increased.

• 한국정밀공학회지
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• 제30권11호
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• pp.1187-1192
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• 2013

In the case of 4 wheel drive (4-WD) type car, power switching occurs to 4-WD by operating lever or switch that operates power switching device attached in transfer case which can operate motor by electric signal. So if the RPM of motor is high, power switching will not exactly occur and can cause damage to gear in transfer case according to circumstances. So in this study, we applied 2 level of planet gear type motor spindle of motor drive part of a power train. And conducted decelerating to increase torque to switch power safe and accurately. Also, we researched efficiency of gear by designing reduction gear ratio and gear type and by calculating contact stress and bending strength. Based on researched content, we made drive head of power switching device and a reduction module which uses type that uses motor spindle as sun gear and ring gear as cover.

• 한국기계가공학회지
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• 제20권6호
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• pp.10-16
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• 2021

Drilling is a crucial process that takes up a significant amount of weight during machining operations. In addition, drill tip-type tools and related operations have been developed for manufacturing industries to achieve economic efficiency. In this study, SM45C carbon steel, widely used for machine structures, was utilized as the working material after quenching and tempering. Insert-tip types of carbide tools, such as TiN and TiAlN, were used as tool materials. Drilling conditions such as the spindle revolution, feed rate, step of cut, and tool diameter were used to measure roughness, roundness, and straightness using the orthogonal array table statistical method. The surface roughness, roundness, and straightness characteristics based on the conditions were analyzed using ANOVA. The results showed that the spindle speed and feed rate were the main factors influencing carbide insert-tip drilling under the same conditions as the experimental conditions.

• 한국정밀공학회지
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• 제22권7호
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• pp.146-154
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• 2005

Recently, the high-speed and intelligence technology of machine tools are developed for the high efficiency of productivity Under the operating condition from the high-speed of machine tools, the various failure modes can occur in core units of manufacturing system. Therefore it is for the reliability concept of machine tool to be required in a design level. And the above-stated technology must be accommodated in the feeding and spindle subsystem, etc those are the core units of machine tools. In this study, we are developed the test-bed of sliding cover (C-plate) in order to evaluating reliability and estimating failure modes of feeding subsystem under operating conditions. The reliability experiment using the developed test-bed and the additional structural analysis executed on single and double structure. We found out the weak parts of sliding cover and were able to predict a life cycle from the experiment results. In this study, we propose the new C-plate model with double link structure to apply the high-speed machine tool in the fundamental guideline.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.144-146
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• 2007

Interior Permanent Magnet Synchronous Motors(IPMSM) are expanding the application extent for industrial applications. Because that High efficiency and wide speed range are required in applications of electric vehicles, spindle drives and compressors and so on. The performance of IPMSM are deeply affected by the current phase control. Therefore, this paper deals with the analysis of the torque performance according to the variation of the current phase angle.

• 한국생산제조학회지
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• 제26권2호
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• pp.257-261
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• 2017

Drilling file is medical mini-drill which is made of Ni-Ti material and has tapered shape. It's for removing teeth nervine which helps the endodontic treatment. All files, saled at domestic market, are imported from U.S. and Europe. Also they have low manufacturing efficiency and high price because it is made by universal 5 axis CNC grinding machine. To solve these problem, 3 axis CNC table, controllable tilting angle spindle and helix angle moving table are devised. To confirm divised CNC grinding machine's manufacturing accuracy, conveying amount and finish product size measurement expreiment has been practiced. Also to automate all manufacturing processes, automatic mechanism is designed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1092-1098
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• 2004

Today the demand of the optical communication components has been increased. Zirconia Ferrule has become the one of the most important elements because it determines transmission efficiency and quality of information in the optical communication system. Grinding is the major process in the ferrule manufacturing process which require high processing precision. In this reseach, specially designed spindle, chucking system, loading & unloading system and cooling system, as a supporting experimental equipment for development of an Intelligent Coaxial Grinding System (ICGS) for Zirconia Ferrule processing, is developed. We are also analized the adaptability of ICGS in practical use, through the way of evaluation for the performance of the each systems above.

• 대한전기학회논문지
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• 제45권3호
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• pp.352-357
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• 1996

Recently, Permanent Magnet Synchronous Motor(PMSM) drives are widely used for industrial applications due to its high efficiency and high power factor control strategy. PMSM generally have two classifications such as the SPMSM(Surface Permanent Magnet Synchronous Motors) and IPMSM(Inter Permanent Magnet Synchronous Motors). IPMSA has economical merits over SPMSM in higher speed range, mechanical robustness, and higher power rate by the geometric difference. The maximum torque operation in IPMSM is realized by the current angle control which is to utilize additional reluctance torque due to a rotor saliency. In traction, spindle and compressor drives, constant power operation with higher speed range are desirable. This is simply achieved in the DC motor drives by the reduction of the field current as the speed is increased. However, in the PMSM, direct control of the magnet flux is not available. The airgap flux can be weakened by the appropriate current angle control to demagnetize. In this paper, the control method of optimal current vector in IPMSM is described in order to obtain the maximum torque or maximum output with the speed and load variations. The applied algorithm is realized by the proto system with torque and speed control Experimental results show this approach is satisfied for the high performance servo applications. (author). 6 refs., 9 figs., 1 tab.

• Clinical and Experimental Reproductive Medicine
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• 제49권2호
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• pp.149-158
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• 2022

Objective: Optimizing culture media for the incubation of immature oocytes is a vital strategy to increase the oocyte maturation rate during in vitro maturation (IVM) programs. This study evaluated the IVM and fertilization rates of human germinal vesicle (GV) and metaphase I (MI) oocytes using two different maturation media (commercial and homemade) with or without growth differentiation factor 9-β (GDF9-β). supplementation. Methods: Immature oocytes from intracytoplasmic sperm injection (ICSI) cycles were collected and assigned to one of two IVM culture media (commercial or homemade; cleavage-stage base). After maturation, MII oocytes were examined under an inverted microscope for the presence of the polar body, zona pellucida (ZP) birefringence, and meiotic spindle (MS) visualization after maturation in four conditions (commercial or homemade medium, with or without GDF9-β. ICSI was done for matured oocytes, and fertilization was confirmed by the visualization of two distinct pronuclei and two polar bodies. Results: No significant differences were found between the two culture media in terms of the time and rate of oocyte maturation or the rate of fertilization (p>0.05). Growth factor supplementation increased the 24-hour maturation rate for both GV and MI oocytes only in homemade medium. The maturation rate after 24 hours was higher for MI oocytes (p<0.05). Similar results were observed for MS visualization and ZP structure in both types of media (p>0.05). Conclusion: Higher rates of oocyte maturation and fertilization were observed after application of homemade medium supplemented with GDF9-β. Therefore, this combination may be recommended as an alternative for clinical IVM programs.