Hwan-Jin Choi

Comparison of Machinability Between PCD Tool and SCD Tool for Large Area Mirror Surface Machining Using Multi-tool by Planer

Mirror surface machining for large area flattening in the display field has a problem such as a tool wear and a increase in machining time due to large area machining. It should be studied to decrease machining time and tool wear. In this paper, multi-tool machining method using a PCD tool and a SCD tool was applied in order to decrease machining time and tool wear. Machining characteristics (cutting force, machined surface and surface roughness) of PCD tool and SCD tool were evaluated in order to apply PCD tool to flattening machining. Based on basic experiments, the PCD/SCD multi-tool method and the SCD single-tool method were compared through surface roughness and machining time for appllying large area mold machining.

Wear characteristics of V shape diamond tool for micro prism pattern with Al alloys

Abstract The ultra-precision machining process using a single crystal diamond tool has been mainly used for machining molds of optical components. Since the micro patterns of various shapes having excellent surface roughness can be machined by using ultra-precision machine tools, the micro pattern on a large light guide plate (LGP) is mainly machined using a diamond tool. The tool wear occurs due to long machining distances and time while machining a large-area LGP mold. The deformation and dimensional error of micro pattern are caused by tool wear, as a result, the light efficiency of LGP declines. The characteristics of tool wear should be analyzed in order to precisely machine large-area LGP mold from all sorts of materials. The experiments were performed in order to compare wear characteristics of a V90° diamond tool using Al3003, 5052, 6061 and 7075. The prism pattern of depth 10 μm was machined in order to analyze characteristics of tool wear according to machining distances (0.5, 1 and 1.5 km). The effects of tool wear on pattern shape were analyzed by applying overlapped cutting depths (Rough machining is (10+8+7) μm and Finish machining is (5+3+2+1) μm) by continuously machining a prism pattern of W shape of 25 μm in depth.

Study on Machining High-Aspect Ratio Micro Barrier Rib Array Structures using Orthogonal Cutting Method

The micro barrier rip array structures have been applied in a variety of areas including as privacy films, micro heat sinks, touch panel and optical waveguide. The increased aspect ratio (AR) of barrier rip array structures is required in order to increase the efficiency and performance of these products. There are several problems such as burr, defect of surface roughness and deformation and breakage of barrier rip structure with machining high-aspect ratio micro barrier rip array structure using orthogonal cutting method. It is essential to develop technological methods to solve these problems. The optimum machining conditions for machining micro barrier rip array structures having high-aspect ratio were determined according to lengths ( and ) and shape angles ( and ) of diamond tool, overlapped cutting depths ( and ), feed rates (100 mm/s) and three machining processes. Based on the optimum machining conditions, micro barrier rib array structures having aspect ratio 30 was machined in this study.

Development of highly-efficient machining method of double-layered micro channels for small mixer using end-milling and metal mold

Micro end-milling is a highly-efficient machining process and can be used to machine high hardness metal mold directly; therefore, it is applied to the machining of micro channel structures. There are conventional methods to fabricate the micro channels such as lithography, etching and laser processing; however, they have some demerits of high cost, limitation of materials and complex processes. Machining molds with micro channel structures for mixers using micro end-mills have been studied. According to recent study, ultra micro end-milling technology is required in order to improve the efficiency of mixers because the micro structures are double-layered channels. Tool breakage and micro burrs are issues due to diameter of the micro end-mill getting smaller. Machining characteristics using Φ 50 and 30 μm end-mill on 64 brass and STAVAX were studied in order to machine the micro complex channels. Tool stability and burrs were studied through analysis of the cutting force and cutting conditions. A micro-mixer mold with double-layered channel structures was machined.

Comparison of Micro Trench Machining Characteristics with Nonferrous Metal and Polymer using Single Diamond Cutting Tool

【Micro trench structures are applied in gratings, security films, wave guides, and micro fluidics. These micro trench structures have commonly been fabricated by micro electro mechanical system (MEMS) process. However, if the micro trench structures are machined using a diamond tool on large area plate, the resulting process is the most effective manufacturing method for products with high quality surfaces and outstanding optical characteristics. A nonferrous metal has been used as a workpiece; recently, and hybrid materials, including polymer materials, have been applied to mold for display fields. Thus, the machining characteristics of polymer materials should be analyzed. In this study, machining characteristics were compared between nonferrous metals and polymer materials using single crystal diamond (SCD) tools; the use of such materials is increasing in machining applications. The experiment was conducted using a square type diamond tool and a shaper machine tool with cutting depths of 2, 4, 6 and 10

Study on ultrafine machining of a complex microlens mold with a lenticular pattern on an aspherical surface

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Analysis of Micro Machining Characteristics using End-milling and Its Applications

and a cutting speed of 200 mm/s. The machined surfaces, chip, and cutting force were compared through the experiment.】

Toward Perfect Light Trapping in Thin-Film Photovoltaic Cells: Full Utilization of the Dual Characteristics of Light

Demand for special optical components having the ability to concentrate and diffuse light effect has increased in order to improve luminance efficiency and function, relative to displays using micro lenses. There is a demand for design and machining technology for optical components that achieve various effects, among them the correction of light aberration and transmittance paths from aspherical surfaces with micro patterns. In this study, micro lens molds were machined that were able to simultaneously concentrate and diffuse light by means of lenticular patterns on aspherical surfaces. Two micro lens molds with micro lenticular pattern (pitch (P) of 10 and 100 μm) were machined on a sine type aspherical surface (amplitude (W) 0.15 mm and period (T) 3.0 mm). The micro lens molds were machined using an ultra-precision DTM (Diamond Turning Machine) and SSS (Slow Slide Servo). The micro lenses were replicated using PMMA resin; then light-transmission measurements were performed to confirm the effectiveness of the shape of various parts of the lenses on light-transmission. It was confirmed by measurement that concentration and diffusion light effects were simultaneously achieved.

Ferrimagnetism in gamma-manganese sesquioxide (gamma-Mn2O3) nanoparticles

Micro structures which are widely used at various fields are commonly fabricated by lithograph, etching and laser methods. Recently, with the emergence of micro tools and ultra-precision machine tools, fabrication of the micro structures obtained using end-milling are studied. However, there are some problems due to the diameter of the micro end-mill getting smaller below . The micro run-out resulted from miniaturization of end-mills have influence seriously on accuracy of micro structures. The error of run-out with a tooling jig showed a decrease of about . Furthermore, micro structures with width of could be applied through experiments of slot machining obtained using 30 and end-mill. Also, narrow angle structures with angle could be applied through analysis of machining acute angle structures. Based on basic experiments, micro fluidics channels and spiral patterns for air bearing were machined.