• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.76-81
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• 2012

The continuing demand for increasingly slimmer and brighter liquid crystal display(LCD) panels has led to an increased focus on the role of the light guide panels(LGPs) or optical films that are used to obtain diffuse, uniform light from the backlight unit(BLU). And the most basic process in the production of such BLU components is the micromachining. LCD BLUs comprise various optical elements such as a LGP, diffuser sheet, prism sheet, and protector sheet with micro patterns. 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 feasibility in microcutting various aspect ratio patterns on electroless nickel plated die materials when using single-crystal diamond tools. Cutting performance was evaluated at various cutting speeds and depths of cut using different machining methods and machine tools.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.4
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• pp.50-56
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• 2007

This study aims to find the optimal cutting conditions, when are IR Detection device HgCdTe is machined with diamond tool of diamond turning machine. Machining technique for HgCdTe with single point diamond turning tool is reported in this paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. It has been found HgCdTe has more and more important applications in the field of modern optics. The purpose of our research is to find the optimum machining conditions for ductile cutting of HgCdTe and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle materials.

• Journal of the Korean Magnetic Resonance Society
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• v.24 no.2
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• pp.59-65
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• 2020

Nitrogen-Vacancy (NV) center in diamond has been an emerging versatile tool for quantum sensing applications. Amongst various applications, nano-scale nuclear magnetic resonance (NMR) using a single or ensemble NV centers has demonstrated promising results, opening possibility of a single molecule NMR for its chemical structural studies or multi-nuclear spin spectroscopy for quantum information science. However, there is a key challenge, which limited the spectral resolution of NMR detection using NV centers; the interrogation duration for NV-NMR detection technique has been limited by the NV sensor spin lifetime (T₁ ~ 3ms), which is orders of magnitude shorter than the coherence times of nuclear spins in bulk liquid samples (T₂ ~ 1s) or intrinsic ¹³C nuclear spins in diamond. Recent studies have shown that quantum memory technique or synchronized readout detection technique can further narrow down the spectral linewidth of NMR signal. In this short review paper, we overview basic concepts of nanoscale NMR using NV centers, and introduce further developments in high spectral resolution NV NMR studies.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1456-1464
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• 1993

The achievable machining accuracy depends upon the level of the micro-engineering, and the dimensional tolerances in the order of 10 nm and surface roughness in the order of 1 nm are the accuracy targets to achieved today. Such requirements cannot be satisfied by the conventional machining processes. Single point diamond turning is one of the new techniques which can produce the parts with such accuracy limits. The aims of this thesis are to get a better understanding of the complex cutting forces. A cutting model for describing the influence of cutting conditions (cutting speed, feedrate and depth of cut), material properties of the workpiece and tool geometry has been proposed after estimating the two cutting force models-the Recht model and the Dautzenberg model. The experiments with Al-alloy workpieces, which have been carried out in order to estimate the models, show that the proposed model in this thesis is better than the two models. As the depth of cut and feedrate are increased in the operations settings (depth of cut 8-100$\mu{m}$, feedrate 8-140$\mu{m}$/rev, and cutting speed 8 m/sec), the relation of dimensionless cutting forces from experiments are similar to the proposed model. With the undeformed chip area of $30-80{\times}10^{2}$\mu{m}^2$, the experimental cutting forces accord with the force prediction.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1995.10a
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• pp.76-81
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• 1995

MgO single crystal is widely used as a the material of high temperature resistance, but is difficult to grind because of brittleness and crack generation. Therefore, superabrasive diamond wheel is required for mirror like grinding of this material. This study describes a newly proposed optimum in-process electrolytic dressing system for carrying out effective dressing of superbrasive diamond wheel. Using this system the grinding surface of MgO single crystal was improved, the grinding force was very l9ow and crack was removed. In conclusion, this system is good to obtain the efficient grinding and mirror-like grinding without crack of MgO single crystal.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.44-49
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• 2003

To obtain the surface roughness with range from 10nm to 1nm we need the study of ultra-precision machine, cutting condition, and materials. In this paper, the optimal cutting conditions for getting mirror surface of aluminum alloy have been examined experimentally by using ultra-precision turning machine and sing1e crystal diamond tool. In generally, the cutting conditions such as feed rate and depth of cut have effect on the surface roughness in ultra-precision turning. The result of surface roughness was measured by the ZYGO New View 200. Therefore, The surface roughness and cutting conditions has been clarified. The smooth surface of aluminum alloy less than 1nm RMS, 1nm Rmax can be obtained by the ultra-precision cutting.

• Journal of the Korean institute of surface engineering
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• v.53 no.6
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• pp.360-368
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• 2020

Wear resistance of cutting tools is one of the most important requirements in terms of the durability of cutting tool itself as well as the machining accuracy of the workpiece. Generally, tungsten carbide ball end mills have been processed with hard coatings for high durability and wear resistance such as diamond coating and tetrahedral amorphous carbon(ta-C) coating. In this study, we developed multilayer ta-C coatings whose wear resistance is comparable to that of diamond coating. First, we prepared single layer ta-C coatings according to the substrate bias voltage and Ar gas flow, and the surface microstructure, raman characteristics, hardness and wear characteristics were evaluated. Then, considering the hardness and wear resistance of the single layer ta-C, we fabricated multilayer coatings consisting of hard and soft layers. As a result, it was confirmed that the wear resistance of the multilayer ta-C coating with hardness of 51 GPa, and elastic recovery rate of 85% improved to 97% compared to that of the diamond coated ball end mill.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1223-1227
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• 2005

Fine microgroove is the key component to fabricate micro-grating, micro-grating lens and so on. Conventional groove fabrication methods such as etching and lithography have some problems in efficiency and surface integrity. This study deals with the creation of ultra-precision micro grooves using non-rotational diamond tool and CNC machining center. The shaping type machining method proposed in the study allows to produce V-shaped grooves of $40\mu{m}$ in depth with enough dimensional accuracy and surface. For the analysis of machining characteristics in micro V-grooving, three components of cutting forces and AE signal are measured and processed. Experimental results showed that large amplitude of cutting forces and AE appeared at the beginning of every cutting path, and cutting forces had a linear relation with the cross-sectional area of uncut chip thickness. From the results of this study, proposed micro V-grooving technique could be successfully applied to forming the precise optical parts like prism patterns on light guide panel of TFT-LCD.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.769-770
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• 2011

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.102-107
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• 1993

The achievable machining accuracy depends upon the level of the micro-engineering, and the dimensional tolerances in the order of 10nm and surface roughness in the order of 1nm are the accuracytargets to be achieved today. Suchrequirements cannot be satisfiedby the conventional machining processes. Single point diamond turning is one of the new techniques which can produce the parts with such accuracy limits. The aims of this thesis are to get a better understanding of the complex cutting process with a diamond tool and, consequently, to develope a predicting modelof a turned surface profile. In order to predict the turned surface profile, a numerical model has been developed. By means of this model, the influences of the cutting conditions, the material properties of the workpiece, the geometry of the cutting tool and the dynamic behaviour of the lathe and their influences via the cutting forces upon the surface roughness have been estimated.