Don-Kyu Lee

NC post-processor for 5-axis milling machine of table-rotating/tilting type

Abstract The free surface machining with more than three axes motion needs CAD/CAM system for the cutter location and orientation data. Since these data are defined with respect to the coordinate system of workpiece, they need converting for machine control commands in machine coordinate system, through processing so called a NC post-processing. Most commercial CAD/CAM software vendors provide these post-processors for each type of 5-axis machines. However, they may cause some erroneous operation during phase reverse process that is due to unsymmetrical operation limits about rotating axes. In this work, efficient algorithms for NC post-processing have been presented for typical 5-axis milling machine of table-rotating/tilting type. The first algorithm is for avoiding the interference between a workpiece and the machine tool during the process of phase reverse. The second is for better strategy of machine path, which needs fewer number of phase reverse processes.

Evaluation of machinability by cutting environments in high-speed milling of difficult-to-cut materials

Abstract High-speed machining of difficult-to-cut materials generates concentrated thermal/frictional damage at the cutting edge of the tool and rapidly decreases the tool life. In this paper, the cutting environments, such as dry, flood coolant, and compressed chilly-air coolant, were investigated to improve the tool life. For this study, a compressed chilly-air system was manufactured. The experiments were performed for various hardened materials and various coated tools. The effectiveness of the developed methods on the basis of tool life was estimated. The results show that the cutting environment using compressed chilly-air coolant provided better tool life than using flood coolant or using a dry environment.

Comparison of transparent conductive indium tin oxide, titanium-doped indium oxide, and fluorine-doped tin oxide films for dye-sensitized solar cell application

In this study, we investigate the photovoltaic performance of transparent conductive indium tin oxide (ITO), titanium-doped indium oxide (ITiO), and fluorine-doped tin oxide (FTO) films. ITO and ITiO films are prepared by radio frequency magnetron sputtering on soda-lime glass substrate at 300 °C, and the FTO film used is a commercial product. We measure the X-ray diffraction patterns, AFM micrographs, transmittance, sheet resistances after heat treatment, and transparent conductive characteristics of each film. The value of electrical resistivity and optical transmittance of the ITiO films was 4.15×10 -4 Ω-cm. The near-infrared ray transmittance of ITiO is the highest for wavelengths over 1,000 nm, which can increase dye sensitization compared to ITO and FTO. The photoconversion efficiency (η) of the dye-sensitized solar cell (DSC) sample using ITiO was 5.64%, whereas it was 2.73% and 6.47% for DSC samples with ITO and FTO, respectively, both at 100 mW/cm 2 light intensity.

Electro-optical characteristics of plasma display panel with Mg1−xSixO protecting thin films deposited by an electron-beam evaporation method

The effect of Si doping in MgO has been investigated in order to improve the material properties of the MgO protecting layer in plasma display panels. A small amount of Si was added to the MgO pellet while the MgO layer was being deposited by using an electron-beam evaporation method. Both the surface characteristics of the protecting layer and the electro-optical properties of 4in. test panels were investigated, such as firing and sustain voltages, luminous efficacy, addressing jitter, and image sticking. The firing voltage is minimized when the Si concentration is 0.03%∼0.04%, where the luminous efficacy increases up to 35% compared with that of the conventional MgO film, and the boundary image sticking also shows good characteristics around the Si concentration level by 0.04%.

14.4: Analysis of Temporal Image Sticking in ac-PDP and the Methods to Reduce It

Intensive experiments have been performed to investigate the origin of temporal image sticking (TIS) in ac-PDP. It has been shown that TIS can be classified into different groups: TIS in background and full-white display. Each one has different memory characteristics at patterned area and boundary between peak white and black patterns. The relationships between TIS and its possible origins such as phosphor degradation, temporal change of MgO layer, wall charge have been discussed. A new driving method to reduce the background image sticking was suggested.

Evaluation of cutter orientations in high-speed ball end milling of cantilever-shaped thin plate

Abstract This work was carried out in order to evaluate machinability in high-speed ball end milling of thin cantilever-shaped aluminum plate, and the effect of tool path, tool angle on geometric accuracy and surface integrity. The experiments were performed at tilt angles 0°, 15°, 45° of workpieces using four cutter orientations (horizontal outward, horizontal inward, vertical outward, vertical inward). Workpiece deflection, surface profile and machined surface have been measured. The results show that when machining cantilever-shaped thin plate, the best cutting strategy is vertical outward at a workpiece tilt angle of 45°.

The effect of a Si-doped protective layer on the discharge characteristics of an alternating current plasma display panel

In order to improve the discharge characteristics such as discharge voltage, luminance, luminous efficacy, high-temperature misfiring, and lifetime, a small amount of Si was added to the MgO protective layer of a plasma display panel. The MgO protective layers were deposited by using an electron-beam evaporation method. The addition of Si onto a MgO protective layer can effectively increase the secondary electron emission coefficient so as to improve the discharge characteristics compared with using a pure MgO film. Both the surface characteristics of the protective layer and the electro-optical properties of 4in. test panels were investigated, such as the discharge voltage, luminance, luminous efficacy, high-temperature misfiring, and lifetime. The results show that Si doping of 0.03%–0.04% in MgO has the best performance on plasma display panels.

21.4: Discharge Characteristics of AC-PDP having Doped MgO Protective Layer in a Variation of Temperature

In order to improve the discharge characteristics such as discharge voltage, luminance, luminous efficacy, temperature dependence of misfiring, a small amount of Si was added to the MgO protective layer of an alternating current plasma display panel (AC-PDP). The effect of Si-doping on a MgO protective layer was reported that it reduces the firing voltage and improved electro-optical characteristics of AC-PDP due to the increase of the secondary electron emission with Si concentration. In this study, it was observed that Si-doping on MgO protective layer reduces the temperature dependence of misfiring compared with a pure MgO film. The effects of Si concentration are reported on the surface-discharge characteristics of an AC-PDP.

P-98: The Effects of Si Doped MgO Protecting Layer in AC PDP

In order to improve the material characteristics of the protective layer for ac-PDPs, a small amount of Si was added to the MgO films. Both the surface characteristics of the protecting layer and the electro-optical properties were investigated, such as discharge voltages, luminance, luminous efficacy, addressing jitter, and image sticking.

A Study on the Relationships between the Electrooptical Characteristics and Working Gas Xe+Ne+Kr

Recently, in order to improve the characteristics of operating voltage, brightness, discharge time lag, luminous efficacy of ac PDP, the PDP with high Xe partial pressure has been investigated. However, the serious problems in this case is to increase the operating voltage of ac PDP. In this study, in order to meet this problem the influences of kr gas in Ne-Xe-Kr ternary gas system is investigated for wide range of Xe partial pressure in terms of operating voltage, driving margin, luminance and luminous efficacy.