• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.225-226
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• 2006

As the technique of high-speed end-milling is widely adopted to machining field. The investigation for microscopic precision of workpiece is necessary for machinability evolution. The environmental pollution has become a big problem in industry and many researcher have investigated in order to preserve the environment. The environmentally conscious machining and technology have more important position in machining process. In the milling process, the cutting fluid has greatly bad influence on the environment. The damaged layer affect mold life and machine parts in machining. In this study, the cutting force, the surface roughness, micro hardness and residual stress is evaluated according to machining environment. Finally, it is obtained that the characteristics of damaged layer in environmentally conscious machining is better than that in conventional machining using cutting fluid.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.629-635
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• 2009

In this research, KP-4, one of the plastic mold steels, was coated with the AlTiN from one layer to four layers by the PVD method in the $\Phi$ 8mm cemented carbide ball end mill. Coated KP-4 was processed with various conditions. For example, slope of $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ the spindle rotation speed was changed from 10,000rpm to 16,000rpm, the tool feeding speed was changed from 1,300mm/min to 1,700mm/min, the depth of cut was also changed from 0.3mm to 0.9mm, and etc. Cutting component force according to the coating layer number, and surface roughness were studied. The cutting component force showed a good agreement better the up ward direction than the down ward direction under all experimental conditions. In case of the condition per the material shape, it was lessen when the tool have larger angle because the average effective diameter of the tool is larger. The surface roughness showed good condition in case of the up ward than the down ward direction. And, in the 3rd layer of AlTiN coating, it showed the most suitable condition.

• Journal of the Korean Ceramic Society
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• v.45 no.1
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• pp.75-81
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• 2008

In this study, machining characteristics of AIN-hBN composites were evaluated in end-milling process. As a first step, AIN-hBN composite specimens with various hBN contents were prepared using hot press method. Material properties of the composites, such as relative density, Young's modulus and fracture toughness, were measured and compared. Then, a series of end-milling experinients were performed under various cutting conditions by changing cutting speed, depth-of-cut and feed rate. Cutting force variations were measured using a tool dynamometer during the cutting experiments. Machined surfaces of the specimens were observed using SEM and a surface pro filer to investigate the surface integrity changes. The cutting force decreased with an increases of hBN content. The cutting process was almost impossible for monolithic AIN, owing to severe chipping. In contrast, at high content of hBN, surface damage and chipping decreased, and better surface roughness can be obtained.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.53-61
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• 2013

A new deformation of reinforcing bar in coils was proposed to improve a machinability of straightening process, which has crescent-shaped transverse ribs with an inclination angle of 50 degrees, a crest width of $0.15d_b$, and a flank inclination of 55 degrees. The proposed deformation can increase contact area between a surface of re-bar and a groove of a roller during a straightening process and, therefore, it might reduce a damage of ribs, improve a final straightness, and enhance an efficiency of the straightening process. Splice tests were conducted to evaluate bond strengths of three types of re-bar in coils including the proposed re-bar, of which the inclination angles of transverse ribs were 50, 60, and 90 degrees, respectively. Test results show that the re-bars in coils have higher bond strengths than predicted strengths by equations of Orangun et al., ACI 408, and KCI by at least 10%. Correlation coefficients of bond strengths between a straight bar and re-bars in coils are 0.94 and more. Consequently, equations of the KCI code for determining development and splice lengths can be applied to the tested re-bars in coils.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.4
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• pp.130-137
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• 1997

The demand for wire-cut EDM is increasing rapidly in the die and tool making industry. In this study machining characteristics such as machining rate, surface roughness, hand drum form and hardness of machined material are investigated experimentally under the conditions varing pulse on time, pulse off time, peak voltage, wire tension after fixing other conditions in SKD 11 and brass and brass workpiece. It was found that various operating conditions had significant influences on machining characteristics. But the hardness of workpiece was uneffected by operating conditions. Also it was obtained experimentally that brass workpeice had better machinability than SKD 11 one.dition according to the current(Ip) in an electric spark machine : 1) Electrode is utilized Cu and Graphite. 2) Work piece is used the material of carbon steel. The condition of experiment is : 1) Current is varied 0.7(A) to 50(A) and the time of electric discharging to work piece in each time is 30(min) to 60(min). 2) After the upper side of work piece was measured in radius(5$\mu$m) of stylus analyzed the surface roughness to ade the table and graph of Rmax by yielding data. 3) Electro wear ratio is : \circled1Cooper was measured ex-machining and post-machining by the electronic balance. \circled2The ex-machining of graphite measured by it, the post-machining was found the data from volume $\times$specific gravity and analyzed to made its table and graph on ground the data. 4) In order to keep the accuracy of voltage affected to the work piece was equipped with the A.V. R and the memory scope was sticked to the electric spark machine. 5) In order to preserve the precision of current, to get rid of the noise occured by internal resistance of electric spark machine and to force injecting for the discharge fluid , it made the fixed table for a work piece to minimize the work error by means of one's failure during the electric discharging.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.133-138
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• 2002

The technique of high speed machining is widely studied in machining fields, because the high efficiency and accuracy in machining can be obtained in high speed machining. Unfortunately the development of tool fur high speed machining in not close behind that of machine tool. In this study, 10 types flat endmill is prepared for obtaining data according to tool shape. Especially, we concentrated in helix angle, number of cutting edge and rake angle. Cutting condition is selected for several experiments and measuring cutting farce, tool life, tool wear and chip shape according to cutting length. 3-axis cutting farces are acquired from the tool dynamometer with high natural frequency, as the conventional tool dynamometer (9257B, Kistler) has cannot measure the state of high frequency force. Particularly, we found out that the axial cutting force waveform has a good relation with tool wear features. And flow is interrupted at the beginning of cutting by the decrease of rake angle. By above results. it is suggested the endmill tool with 45$^{\circ}$helix angle, 6 cutting edge and -15$^{\circ}$rake angle is suitable for high speed machining.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.263-267
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• 2013

The continuing demand for increasingly slimmer and brighter liquid crystal display (LCD) panels has led to an increased focus on the role of light guide panels (LGPs) or optical films that are used to obtain diffuse, uniform light from the backlight unit (BLU). The most basic process in the production of such BLU components is the micromachining of V-shaped grooves. Thus, given the current trend, micromachining of V-shaped grooves is expected to play increasingly important roles in today's manufacturing technology. LCD BLUs comprise various optical elements such as a LGP, diffuser sheet, prism sheet, and protector sheet with V-shaped grooves. High-aspect-ratio patterns are required to reduce the number of sheets and enhance light efficiency, but there is a limit to the aspect ratio achievable for a given material and cutting tool. Therefore, this study comprised a series of experimental evaluations conducted to determine the machining limit in microcutting V-shaped grooves on electroless nickel plated die materials when using single-crystal diamond tools with point angles of $20^{\circ}-80^{\circ}$. Cutting performance was evaluated at various cutting speeds and depths of cut using different machining methods and machine tools. The experimental results are that V-shaped patterns with angles of $80^{\circ}$ or up can be realized regardless of the machining conditions and equipment. Moreover, the feed rate has little effect on machinability, and it is thought that the fly-cut method is more efficient for shallow patterns.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.36-41
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• 2017

In this paper, $Si_3N_4/hBN$ ceramics with various hexagonal boron nitride (hBN) contents (0, 10, 20, or 30 wt%) were fabricated via spark plasma sintering (SPS) at $1500^{\circ}C$, 50MPa, and 10m holding time. The material properties such as the relative density, hardness, and fracture toughness were systematically evaluated according to the hBN content in the $Si_3N_4/hBN$ ceramics. The results show that relative density, hardness, and fracture toughness continuously decreased as the hBN content increased. In addition, peak-step drilling (with tool diameter $500{\mu}m$) was performed to observe the effects of hBN content in micro-hole shape and cutting force. A machined hole diameter of $510{\mu}m$ (entrance) and stable cutting force were obtained at 30 wt% hBN content. Consequently, $Si_3N_4/30wt%$ hBN ceramic is a feasible material upon which to apply semi-conductor components, and this study is very meaningful for determining correlations between material properties and machining performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.313-318
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• 2013

Magnetic abrasive polishing is an advanced deburring process for nonmagnetic materials and micropattern products that have non-machinability characteristics. Despite these advantages, there are some problems with using MAP for deburring. MAP has introduced geometric errors into microgrooves because of an over-cutting force caused by uncontrolled magnetic abrasives in the MAP tool. Thus, in this study, to solve this problem, an EP (electrolyte polishing)-MAP hybrid polishing process was developed for deburring microgrooves in an STS316 material. In addition, an evaluation of EP-MAP for the deburring of microgrooves was carried out by profiling the burrs. The results of the experiment showed geometric errors after the deburring process using MAP. However, in the case of EP-MAP, no geometric error was observed after the process because of the lower material removal rate in EP-MAP.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.975-986
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• 2013

This paper dealt with the fabrication and performance evaluation of the electronics housing made of lightweight composite materials, aiming at the enhancement of satellite mass savings by replacing conventional aluminum alloy widely used for satellite avionics with lightweight composite material. For this purpose, a fabrication process was designed to overcome low machinability of CFRP and to minimize the post-treatment. The composite housing with grid-stiffened and monolithic frame was made using co-curing method. Its performance was also evaluated regarding endurance, stiffness, thermal conductivity, electrical grounding, EMI protection and radiation shielding. The composite housing can provide the considerable mass savings over the aluminum housing with same dimension.