• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1645-1651
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• 2015

This paper describes the changes of shape accuracy in workpiece materials depending on the turning clearance angle. The experiments started from choosing three workpiece materials, SM45C(machine structural carbon steel), STS303(stainless steel) and SCM415 (chrome-molybdenum steel). The experiments showed specifically how features of selected materials changed when they were processed with diverse machining depths, 0.1 mm, 0.2 mm and 0.3 mm, with various negative angles, $0.0^{\circ}(-6.0^{\circ})$, $0.3^{\circ}(-6.3^{\circ})$ and $0.9^{\circ}(-6.9^{\circ})$, and called cutting edge inclination starting from a fixed rotational speed, 2,500 rpm, focusing on the feed rate, 0.07 mm/rev and 0.10 mm/rev. The results of the accuracy of processing, cylindricity, deviation from coaxiality, etc. were compared using the graph and table. The accuracy of cylindricity in the order of degree $0.0^{\circ}{\rightarrow}0.3^{\circ}{\rightarrow}0.9^{\circ}$ depending on the workpiece materials showed the best cylindricity when it was $0.9^{\circ}$. In conclusion, the accuracy improved in specific degrees irrespective of the quality of the materials when the bite negative angles increased. This means that workability improved in these experiments. In addition, the processing shape changed depending on depth of the cut and feed rate.

• Journal of Internet of Things and Convergence
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• v.6 no.4
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• pp.21-26
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• 2020

An autonomous driving system is based on the deep learning system built by big data which are obtained by various IoT sensors. The miniaturization and high performance of the IoT sensors are needed for diverse devices including the autonomous driving system. Specially, the miniaturization of the sensors leads to compel the miniaturization of the fixer structures. In the viewpoint of the miniaturization, metallic structure is a best solution to attach the small IoT sensors to the main body. However, it is hard to manufacture the small metallic structure with a conventional machining process or manufacturing cost greatly increases. As one of solutions for the problems, in this work, metallic FDM (Fused depositon modeling) based on metallic filament was proposed and the FDM process was investigated to fabricate the small metallic structure. Final part was obtained by the post-process that consists of debinding and sintering. In this work, the relationship between infill rate and the density of the part after the post-process was investigated. The investigation of the relationship is based on the fact that the infill rate and the density obtained from the post-processing is not same. It can be said that this work is a fundamental research to obtain the higher density of the printed part.

• Journal of the Korean Ceramic Society
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• v.42 no.6 s.277
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• pp.377-383
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• 2005

Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness, as compared with the original glass. This improvement is due to the microstructure consisting of very small crystals. In this study, Ag-doped $45SiO_2-24CaO-24Na_2O-4P_2O_5$ glasses were irradiated to strengthen by the crystallization using Femto second laser Pulses. Through the UV/VIS spectroscope, XRD, Nano-indenter and SEM etc., heat-treated and irradiation of laser pulses without heat-treated samples were analyzed. Two kinds of samples, heat-treated and laser irradiated without heat-treated samples, showed the peaks in the same wavelength near 360 nm. Especially, samples irradiated by 140 mW laser with XYZ stage having at the rate of 100$\~$l000 $\mu$m/s had the largest absorption peak among them, and heat-treated samples was shown lower absorption range than over 90 mW laser irradiated samples. Moreover, samples irradiated by laser had higher values ($4.4\~4.56{\times}10^{-3}(Pa)$) of elastic modulus which related with strength of glass than values of heat-treated samples and these are 1.2$\~$1 .5 times higher values than them of mother glass.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.38-45
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• 2007

A liquid rocket engine fuel-rich gas generator has been developed for the first time in the country, which can produce combustion gas over the rate of 4 kg/s at 900 K and 58 bar. The gas is not only for driving a turbopump but also for providing heat source for propellant supply tanks. The final design of the gas generator had been fixed based on the concept and preliminary development tests, and was validated through structure and heat transfer analysis. The manufacturing involved precision machining, surface finish, and special welding technique. The final assessment on the characteristics of ignition and combustion had been carried out for two different versions of injector heads. This concluded that the present product satisfies the development requirements such as spatial temperature distribution and the development has been successful.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.181-185
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• 2006

A liquid rocket fuel-rich gas generator developed for the first time in the country can produce combustion gas over the rate of 4 kg/s at 900 K and 58 bar. The gas can be used not only for driving a turbopump but also for providing heat source for propellant supply tanks. The final design of the gas generator has been fixed based on the concept and preliminary development tests, and was validated through structure and heat transfer analysis. The manufacturing involves precision machining, special surface finish, and welding techniques. The final assessment on the characteristics of ignition and combustion had been carried out through five combustion tests. This concluded that the present product satisfies the development requirements.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.2
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• pp.123-128
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• 2007

The demand for the precision rubber products has been rapidly increasing with the recent growth of industries. And the requirement for the productivity and the quality calls out for the injection molding machines with the precision machining ability as well as the high productivity. Especially modern automobile industry is in urgent need of developing injection molding machines for the high quality rubber products with high productivity. And the inability of the domestic companies to meet the standards causes importing foreign machines and as a result spending good amount of dollars. It is extremely important to develop competitive machines and strengthen the infrastructure of the related industries. In this paper the functions and the structure of a automatic multi-nozzle injection molding machine has been studied to set up a proper test system for the precision rate and the reliability of the machines, which can help build the machines to meet the request of the industry.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.11
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• pp.1121-1128
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• 2013

Ultrasonic grinding system is that the ultrasonic vibration by ultrasonic actuator is applied on conventional grinding system during grinding process. The Ultrasonic vibration with a frequency of over 20kHz can reduce grinding forces and increase surface quality, material removal rate (MRR) and grinding wheel life. In addition, ultrasonic vibration assisted grinding can be used for the materials that are difficult to cut. In this paper, methodology for ultrasonic tools is studied based on finite element method, and in turn the ultrasonic tools are designed and fabricated. It is found that the ultrasonic tool can vibrate with a frequency of 20kHz and amplitude of $25{\mu}m$. In order to verify the machining performance, the grinding experiment is performed on titanium alloy. By applying ultrasonic vibration, the grinding force and temperature are reduced and MRR is increased compared with the conventional grinding.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.2
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• pp.99-105
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• 2009

Among a few items with world wide competitiveness are the semiconductor and the LCD. Grinding/polishing is the most significant process in manufacturing semiconductor wafers and LCD panels, the most critical quality of which is the precision rate of the machined surfaces. It is well known that the control of the vibrations is the major factor in maintaining superb machined surfaces. In this paper the dynamic properties of a grinding machine have been investigated through the frequency analysis test and the computer simulation to deduce ideas of design modifications for improved stability. The alterations have been applied to the simulation model, which is supposed to have identical dynamic property with the original structure, to identify the effects and to finally achieve the satisfactory level of stability. The result shows that the machine can have much improved stability with relatively simple design changes, and also can improve the surface quality of the products.

• Journal of the Semiconductor & Display Technology
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• v.2 no.4
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• pp.37-40
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• 2003

We have studied micro-machining technologies to fabricate parts and sensors used in the semiconductor equipment. The studies were based on the silicon integrated circuit processes, and composed of the anisotropic etching of single crystal silicon to fabricate a membrane structure for hot and cold junctions in the infrared absorber. KOH and TMAH were used as etching solutions for the anisotropic wet etching for membrane structure formation. The etching characteristic was observed for the each solution, and etching rate was measured depending upon the temperature and concentration of the etching solution. The different characteristics were observed according to pattern directions and etchant concentration. The pattern was made to incline $45^{\circ}$ on the primary flat, and optimum etching property was obtained in the case of 30 wt% and $90^{\circ}C$ of KOH etching solution for the formation of the membrane structure.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.104-111
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• 2008

The objective of this study is to evaluate micro end-milling characteristics and tool wear behavior of AlN-hBN composites. First, AlN based composites with hBN contents in the range of 10 to 20vol% were prepared by hot-pressing. Vickers hardness and flexural strength of the prepared composite specimens were measured and compared according to the vol% of hBN variations. Then, cutting force variations were measured and analyzed using a tool dynamometer during the micro end-milling experiments; and machined surface shapes and roughness were investigated using a 3D non-contact type surface profiler. After micro end-milling, worn tools were investigated using a tool microscope and SEM images. From the experimental results, it can be observed that the cutting forces decreased, and surface qualities were improved with increasing hBN contents. At low content of hBN, tool chipping was observed; and tool wear rate decreased with increasing hBN contents. The results of this study insist that proper machining conditions, including tool wear behavior investigation, should be determined for the micro end-milling of AlN-hBN composites for its further application.