• 대한기계학회논문집
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• 제19권5호
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• pp.1176-1181
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• 1995

Microdrilling is one of the most difficult operations because of the poor chip discharge and the weakness of tool. This study is concerned about the development of a microdrilling monitoring system that is useful for minimizing the tool breakage and enhancing the machinability in the air spindle based microdrilling. The system is composed of a drilling state detection unit and an adaptive step-feed control unit that controls the micro-stepping motor driven spindle axis. Drilling states such as overload, tood breakage are recognized by the change of the air spindle speed which is measured via the reflective photo sensor. Based on the monitoring results, the adaptive step-feed control algorithm adjusts the step increment to keep the decrease of spindle speed within a specified range. The results of evaluation tests have shown that the developed system is very effective to prevent the breakage of microdrill and improves the productivity in comparison with the conventional microdrilling.

• 한국정밀공학회지
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• 제14권10호
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• pp.15-27
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• 1997

Quasti-static cutting force variations in milling process are measured indirectly using spindle motor current. Quasi-static sensitivity of the spindle motor current is higher than that of the feed motor current. Magnitude of the spindle motor current is independent of cutting direction. The linear relationship between the cutting force and the spimdle motor RMS current at various spindle rotational speed is obtained. Frequency/ Voltage(F/V) converter voltage is measured to identify the spindle speed and to determine the cutting force at various spindle speeds. Overload on the tool during milling process can be detected using the proposed indirect cutting force measurement. Based on these measurements, cutting force is regulated at a constant level by feedrate control.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.601-606
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• 2001

Free vibration analysis was performed for a spinning disk/spindle system mounted on a flexible baseplate. A simplified model was presented considering the effects of the baseplate flexibility on a disk/spindle system, and the equations of motion were derived by the assumed mode method and Lagrange's equation. From the results of the tree vibration analysis, the variations of the natural frequencies were investigated by changing rotating speed, baseplate thickness. They were attributed to the coupling between the flexible modes of the spinning disk/spindle system and the baseplate. This simplified model was used to predict the dynamic characteristics of a small size disk drive. The validity of the simplified model was verified by experiments and FE analysis.

• Tribology and Lubricants
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• 제13권4호
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• pp.47-52
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• 1997

Friction torques, electrical contact resistances and bearing temperatures were measured on high speed angular contact ball beatings for the spindle of machine tools. The test bearings ran with oil-air lubrication at the thrust loads from 320 N to 1920 N and at the rotational speed of up to 12000 rpm. Electrical contact resistances between balls and races were measured to evaluate the formation of the lubricant film in the contact area. The test results with sufficient lubrication showed that the variations of friction torques were sensitive to the thrust loads and the rotational speeds, and that the friction torques were higher than those with insufficient lubrication. With insufficient lubrication and high thrust loads, the collapse of the lubricant film was detected even at a high rotational speed. It was concluded that these high speed beatings to run in condition of fluid lubrication should require monitoring not only the temperature increase of the bearing but also the lubricant film formation in contact areas resulting from the change in the applied load and the lubricant amount.

• 소성∙가공
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• 제30권1호
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• pp.27-34
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• 2021

In this study, response surface method (RSM) was used in modeling and multi-objective optimization of the parameters of AA5052-H32 in incremental sheet forming (ISF). The goals of optimization were the maximum forming angle, minimum thickness reduction, and minimum surface roughness, with varying values in response to changes in production process parameters, such as tool diameter, tool spindle speed, step depth, and tool feed rate. A Box-Behnken experimental design (BBD) was used to develop an RSM model for modeling the variations in the forming angle, thickness reduction, and surface roughness in response to variations in process parameters. Subsequently, the RSM model was used as the fitness function for multi-objective optimization of the ISF process based on experimental design. The results showed that RSM can be effectively used to control the forming angle, thickness reduction, and surface roughness.

• 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.

• 풍력에너지저널
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• 제10권4호
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• pp.20-27
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• 2019

High-speed shaft coupling in a wind power system transmits power and absorbs variations in length and spindle dislocation between the gearbox and generator. Furthermore, the coupling has an insulation function that prevents electrical corrosion caused by the flow of the generator's current into the gearbox and prevents overload resulting from sudden power failure from being transferred to the gearbox. Its design, functions, and part verification are described in the IEC61400 and GL Guidelines, which specify that the part must have a durability life of 20 years or longer under distance variation and axial misalignment between the gearbox and the generator. This study presents the design of a high-speed coupling through composite stiffness calculation, structural analysis, and comparative analysis of test and theory to identify the characteristics of high-speed coupling for a large-capacity 6 MW wind power generator. A prototype was fabricated by optimizing the manufacturing process for each part based on the design, and the reliability of the fabricated prototype was verified by evaluating the performance of the target quantitative evaluation items.

• 한국생산제조학회지
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• 제21권6호
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• pp.932-937
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• 2012

In the presented study, SM45C carbon steel parts were joined by friction welding. The welding process was carried out under optimized conditions using statistical approach. The study of SM45C is conducted with various combinations of process parameters. Parameter optimization, microstructure and mechanical property correlation are the major contribution of the study. The welded joints were produced by varying spindle revolution speed, friction pressure, upset pressure and burn-off length. Tension tests were applied to welded parts to obtain the strength of the joints. Fracturs properties were additionally obtained experimentally under fluctuated tensile loads. Microstructures using microphotographs were examined in the weld interface and weld region and heat affected zone and base metal and flash zone of welded parts. Finally, Hardness variations in welding zone and base metal were also obtained. Through these tests, the optimum conditions of parameters for ${\phi}20$ SM45C in friction welding were obtained when the friction spindle revolution was 1,950 rpm, the friction pressures was 30 MPs, upset pressures was 50 MPs.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.199-202
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• 2005

High speed milling process is emerging as an important fabrication process benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry. It also enables the creation of micro and meso-scale molds for injection molding. Factors affecting surface roughness have not been studied in depth for this process. A series of experiments has been conducted in order to begin to characterize the factors affecting surface roughness and determine the range of attainable surface roughness values for the high speed milling process. It has previously been shown that run-out creates a greater problem for the dimensional accuracy of parts created by high speed milling process. And run-out also has a more significant effect on the surface quality of milled parts. The surface roughness traces reveal large peak to valley variations. This run-out is generated by spindle dynamics and tool geometry. In order to investigate the relationship between tool setting errors and surface roughness end tilted mills were used to cut aluminum samples. The results indicate that tool setting errors have significant effects on surface roughness and cutting forces.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.627-628
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• 2006

High speed milling process is emerging as an important fabrication process benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry. It also enables the creation of micro and meso-scale molds for injection molding. Factors affecting surface roughness have not been studied in depth for this process. A series of experiments has been conducted in order to begin to characterize the factors affecting surface roughness and determine the range of attainable surface roughness values for the high speed milling process. It has previously been shown that run-out creates a greater problem for the dimensional accuracy of pans created by high speed milling process. And run-out also has a more significant effect on the surface quality of milled parts. The surface roughness traces reveal large peak to valley variations. This run-out is generated by spindle dynamics and tool geometry. In order to investigate the relationship between tool alignment errors and surface roughness the scallop generating mechanism in the ball-end milling with tool alignement errors has been studied and simulated. The results indicate that tool alignment errors have no significant effects ell the dimension of scallops in for flat planes.