• Journal of the Korean Society for Heat Treatment
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• v.30 no.5
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• pp.222-226
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• 2017

Recently sapphire wafer has expected as smart phone cover material, however, brittle nature of sapphire needed edge grinding processes to prevent early initiation of cracks. Electro-deposited multi-layered groove tools with $35{\mu}m$ diamond particles were studied for sapphire wafer grinding. Solid particle flow behaviors in agitated electrolyte was studied using PIV(Particle Image Velocimetry), and uniform particle distribution in Ni bond were obtained when agitating impeller was located lower part of electrolyte. Hardness values of $400{\pm}50Hv$ were maintained for retention of diamond particles in electro-deposited bond layer. Sapphire wafer edge grinding test was carried out and multi-layered $160{\mu}m$ thick diamond tool showed much greater grinding capabilities up to 2000 sapphire wafers than single-layered $50{\mu}m$ thick diamond electro-deposited tools of 420 wafers. The reason why 3 times thicker multi-layered tools than single-layered tools showed 5 times longer tool lives in grinding processes was attributed to self-dressed new diamond particles in multi-layered tools, and multi-layered diamond tools could be promising for sapphire grinding.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1641-1646
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• 2011

The second-generation magnetic abrasive polishing is one of the nontraditional machining technologies newly developed. Because of the flexibility effect in magnetic abrasive polishing, the precise and mirror like surface can be obtained during this process. In this study, magnetic abrasive polishing process was applied in small grooved surface. As a result, it was seen that the flexible magnetic abrasive tool was effective to remove burrs on the edge of the groove. However, the efficiency of magnetic abrasive polishing at the slot was very low according to increasing depth and width of slot. So, correlation between geometric parameters, such as the depth and width, and surface roughness was evaluated and the minimum width for suitable polishing was found by experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.625-628
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• 2005

For precise micro-grooving and surface machining, ultrasonic cyclic elliptical cutting is proposed using two parallel piezoelectric actuators. The piezoelectric actuators are energized by sinusoidal voltages of varying phase which is essenstial to generating elliptical cutting. Experimental setup is composed of ultrasonic motor, single crystal diamond cutting tool, and precise motorized xyz stage. It is confirmed experimentally that the cutting performance, in terms of the cutting force, the burr formation, and the discontinuous chip formation is improved remarkably by applying ultrasonic elliptical vibration cutting.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.576-581
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• 2012

A 23 W continuous wavelength $CO_2$ laser system exited by a high-frequency LCC resonant converter is adapted to cut a biodegradable rope fabricated with polybutylene succinate. As the biodegradable rope consists of three twisted strands, the thickness changes relative to the position of the laser beam and we thus propose a method to determine exact cutting depth. In order to obtain the parameters related to the rope cutting, the experimental and theoretical cutting depths are compared and analyzed for a range of laser heat sources. The melted thickness and groove width of the cut biodegradable rope are also examined. The proposed theoretical cutting depth depends on the incident power and target velocity ratio. From these experimental results, the biodegradable rope with a diameter of 22 mm can be cut with a heat source of 50 J/cm resulting in a melted thickness of 1.96 mm and a groove width of 0.65 mm. The laser system is shown to be perfect tool for the processing of biodegradable rope without the occurrence of raveling.

• Journal of Powder Materials
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• v.22 no.3
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• pp.169-174
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• 2015

The optical film for light luminance improvement of BLU that is used in LCD/LED and retro-reflective film is used as luminous sign consist of square and triangular pyramid structure pattern based on V-shape micro prism pattern. In this study, we analyzed machining characteristics of Cu-plated flat mold by shaping with diamond tool. First, cutting conditions were optimizing as V-groove machining for the experiment of micro prism structure mold machining with prism pattern shape, cutting force and roughness. Second, the micro prism structure such as square and triangular pyramid pattern were machined by cross machining method with optimizing cutting conditions. Burr and chip shape were discussed with material properties and machining method.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.28-33
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• 2005

Recently, trends of TFT-LCD toward larger scale and thinner thickness continue. so, demands of Light Guide Panel (LGP) which is to substitute for prism sheet are appeared. Functions of LGP obtaining polarization of light of the prism sheet as well as the incidence and reflection of light are demanded. This prism type LGP to complete functions of the existing LGP and polarization at once must be supported by micro machining technology of LGP surface. In this research, the machining characteristics of the various materials were analysed by shaping using V-shaped single crystal diamond tool. The characteristics are machined surface, machining force due to the variation of cutting depth. Used specimens are engineering materials, which are 6:4 brass, oxygen-free copper, Al6061, PC, PMMA. The FFT analysis of the measured cutting force was conducted. The cutting characteristics were analyzed and the optimum cutting conditions with materials were established.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.130-136
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• 2001

Generally, a metal slitting saw is plain milling cutter with thickness less than 3/16 inch. This is used for cutting a workpiece that high dimensional accuracy and surface finish is necessary. A small thin milling cutter like a metal slitting saw is useful for machining a narrow groove. In this case, built up edge(BUE) is severe at each tooth and affects the surface integrity of the machined surface and tool wear. It is well known that tool geometry and cutting conditions are decisive factors to remove BUE. In this paper, we optimized the geometry of the milling cutter and selected cutting conditions to remove BUE by the experimental investigation. The experiment was planned with Taguchi method based on the orthogonal array of design factors such as coating, rake angle, number of tooth, cutting speed, feed rate. Response table was obtained from the number of built-up edge generated at tooth. The optimized tool geometry and cutting conditions could be determined through response table. In addition, the relative effect of factors was identified bh the analysis of variance (ANOVA). Finally, coating and cutting speed turned out important factors for BUE.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1597-1600
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• 2005

Recently, the trends of TFT-LCD are large scale and thin thickness, so, the demands of Light Guide Panel(LGP) which is able to substitute for prism sheets are appeared. Functions of LGP obtaining polarization of light of the prism sheet as well as the incidence and reflection of light are demanded. This prismless type LGP to complete functions of the existing LGP and polarization at once must be supported by micro machining technology of LGP surface. In this research, we have used the STAMPER method for the mass product and In-Line process, and the optimized conditions are established by analyzing the cutting force and conditions according to the material and processing properties when the prismless type LGP mold is fabricated. Parameters of the cutting condition were the workpiece and cutting depth.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.77-86
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• 2019

The purpose of this study was to reveal how the agility of fingers directly involved in the use of mobile phones, a necessity for modern people, is related to the amount of text usage. To find out, 95 people who agreed to the purpose of this research without any limitation on visual and upper-geometry were selected. The research period was from June 27, 2018 to July 31, 2018. The evaluation tool used in this study was Grooved Pegboard, a standardized evaluation tool that measures hand dexterity, and the general characteristics of examinees such as age, text message amount, and a hand that using for text messages were investigated through interviews. Since text input methods vary depending on mobile phone types, unfamiliar methods of typing mobile phone characters can affect the speed of texting. As a result, there were significant differences in hand dexterity between age and gender. The rate of texting and hand dexterity were statistically significantly faster than those in their 20s and 30s (p<0.05), and in gender, women showed significantly faster texting and hand dexterity than men (p<0.05). However, it was not statistically significant to text usage and to the dexterity of the hand.

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.83-86
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• 2003

In this paper, arbitrary pulse power for electro chemical etching, which manufactures the groove of fluid dynamic bearing and aero dynamic bearing, is presented. For high precision manufacture, we generally use high precision CNC machine. However, this case has the disadvantage that cost is very expensive and bur due to bites of tool can be generated. So most of companies are interested in the method of electro chemical etching. But for more precision results, it is important to decision the parameters of electrical conditions, such as currents and frequency. We designed and made the arbitrary pulse power system easy to input the parameters for optimal conditions. Experimental results show the effectiveness of the system strategy proposed for the high precision manufacture.