• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.775-778
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• 2000

Single point diamond turning technique fur optical crystals is reported in this paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability. The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. SPDT has been widely used in manufacturing optical reflectors of non-ferrous metals such as aluminum and copper which are easy to be machined for their proper ductility. But optical crystals being discussed here are characterized by their high brittleness which makes it difficult to obtain high quality optical surfaces on them. The purpose of cur research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle materials. As a result, the cutting force is steady, the cutting force range is 0.05-0.08N. The surface roughness is good when spindle is above 1400rpm. and feed rate is small. The influence of depth of cut is very small.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.11
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• pp.905-910
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• 2016

Infrared (IR) optic lens can be fabricated by a single point diamond turning (SPDT) machine without subsequent polishing process. However, this machining process often leaves micro-cracks that deteriorate the surface quality. In this work, we propose an experimental design to remove micro-cracks on IR lens. The proposed design gathered data between cutting process condition and Rt surface roughness. This is of great importance because the scale of micro-cracks is a few micrometer. Rt surface roughness is suitable for analyzing maximum peak height signals of the profile. The experimental results indicate that feed per revolution variable is one of the most dominant variable, affecting the generation micro-cracks on IR lens surfaces.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.48-54
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• 2012

In recent years, developments in the semiconductor and electronic industries have brought a rapid increase in the use of large size silicon. However, for many companies, it is hard to produce 400mm or 450mm wafers, because of excesive funds for exchange the equipments. Therefore, it is necessary to investigate 300mm wafer to obtain a better efficiency and a good property rate. Polishing is one of the important methods in manufacturing of Si wafers and in thinning of completed device wafers. This research investigated the surface characteristics that apply variable machining conditions and Taguchi Method was used to obtain more flexible and optimal condition. In this study, the machining conditions have head speed, oscillation speed and polishing time. By using optimum condition, it achieves a ultra precision mirror like surface.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.2
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• pp.138-143
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• 2000

The establishment of a practical ultra-precision grinding technique using Diamond and CBN wheels is one of the major key technolo-gies to improve production techniques for machine-to-difficult materials without finishing process such as lapping and polishing. But the special efficient dressing technique for ultra-fine grit type grinding wheels to stabilize the grinding ability was not developed. Recently electrolytic in-process dressing technique is proposed to ultra-fine grit type metal bonded diamond wheels to protrude abra-sives continuously from the tool surface. This technology can be widely used to surface grinding and cylindrical grinding but cannot be used efficiently to internal grinding because of the electrode attachment trouble. This paper describes the effect of interval type electrolytic dressing as proposed newly to cast iron bonded diamond wheel for efficient internal grinding with mirror type high quality ground surface.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.3
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• pp.36-42
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• 2015

The aspherical lens was designed to be able to array a focal point. For this reason, it has very curved surface. The aspherical lens is fabricated by injection molding or diamond turning machine. With the aspherical lens, tool marks and surface roughness affect the optical characteristics, such as transmissivity. However, it is difficult to polish free form surface shapes uniformly with conventional methods. Therefore, in this paper, the ultra-precision polishing method with MR fluid was used to polish an aspherical lens with 4-axis position control systems. A Tool path and polishing mechanism were developed to polish the aspherical lens shape. An MR polishing experiment was performed using a generated tool path with a PMMA aspherical lens after the turning process. As a result, surface roughness was improved from $R_a=40.99nm$, $R_{max}=357.1nm$ to $R_a=4.54nm$, $R_{max}=35.72nm$. Finally, the MR polishing system can be applied to the finishing process of fabrication of the aspherical lens.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.86-89
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• 2003

Chemical Mechanical Planarization(CMP) has been accepted as the most effective processes for ultra large scale integrated (ULSI) chip manufacturing. However, as the polishing process continues, pad pores get to be glazed by polishing residues, which hinder the supply of new slurry. And pad surface is ununiformly deformed as real contact distance. These defects make material removal rate(MRR) decrease with a number of polishied wafer. Also the desired within-chip planarity, within wafer non-uniformity(WIWNU) and wafer to wafer non-uniformity(WTWNU) arc unable to be achieved. So, pad conditioning in CMP Process is essential to overcome these defects. The eletroplated or brazed diamond conditioner is used as the conventional conditioning. And. allumina long fiber, the jet power of high pressure deionized water, vacuum compression. ultrasonic conditioner aided by cavitation effect and ceramic plate conditioner are once used or under investigation. But. these methods arc not sufficient for ununiformly deformed pad surface and the limits of conditioning effect. So this paper focuses on the characteristics of diamond conditioner which reopens glazed pores and removes ununiformly deformed pad away.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.179-185
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• 2004

Surface finish technology is highly demanded in the wide field of industry applications from ultra-precision parts to rough casting parts. Therefore, many kinds of surface finish technologies have been developed for each purpose. Because surface of a car's wheel cast is very rough it becomes the reason of the corrosion. This surface is coated to complement such problem but because surface is rough, the result of coating is not good and the coated metal peels off well. Therefore before the wheel is coated, it is necessary to grind the surface. In this study, we devised the plant to apply a barrel machining to improve the surface roughness and enhance the productivity. Also we could obtain the optimum barrel machining conditions for the proper surface roughness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.939-942
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• 2000

Single point diamond turning technique for optical crystals is reported in this paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability. The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. The purpose of our research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle material.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.1
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• pp.57-62
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• 2003

Machining technique for optical crystals with single point diamond turning tool is reported in tills paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. SPDT has been widely used in manufacturing optical reflectors of non-ferrous metals such as aluminum and copper which are easy to be machined for their proper ductility. But optical crystals being discussed here are characterized by their high brittleness which makes it difficult to obtain high quality optical surfaces on them. The purpose of our research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle materials. As a result, the cutting force is steady, the cutting force range is 0.05-0.08N. The surface roughness is good when spindle is above 1400rpm, and feed rate is small. The influence of depth of cut is very small.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.2
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• pp.31-36
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• 2005

Machining technique for optical crystals with single point diamond turning tool is reported in this paper. The main factors influencing the machined surface quality are studied and regularities of machining process are drawn. Optical crystals have been known to more and more important applications in the field of modern optics. Ge is more brittle material of poor machinability. The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. The purpose of our research is to find the optimum machining conditions for ductile cutting of Ge and apply the SPDTM technique to the manufacturing of ultra precision optical components of Ge. As a result, the surface roughness is the best when cutting speed is 180m/min, feed rate is 2mm/min, depth of cut is $0.5{\mu}m$ and nose radius of tool is 0.8mm.