• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.191-195
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• 2012

Heavy flint optical glass(SF57HHT) is new material that has extremely high transmittance. Due to brittleness and high hardness, optical glass is one of the most difficult to materials for ultra-precision turning. According to the hypothesis of ductile machining, all materials, regardless of their hardness and brittleness, will undergo transition from brittle to ductile machining region below critical undefromed chip thickness. In this study, cutting test was carried out to evaluate cutting performance of heavy flint glass using ultra-precision machine with single crystal diamond bite. The machined workpiece surface topography, tool wear and surface roughness were examined using AFM and SEM. The experimental results indicate that the machining mode become the brittle mode to ductile mode, when the maximum undeformed chip thinkness is large than critical value. Tool wear mainly occurs on the flank face and its wear mechanism is dominated by abrasion. This study demonstrates the feasibility of SF57HHT by diamond turning.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.1
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• pp.11-15
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• 2007

Composite materials are widely used to make all kinds of machine parts, internal and structural materials of cars, aerospace components, building structures, ship materials, sporting goods and others, It is worth while to use composite space substitute material in various applications when compared with others. But the use of composite material is limited in the field of the mechanical processing because of the difficulties in processing. Thus, it is proved that the surface is rough at the in and out sections of the hole processing when the GFRP is machined with HSS drill in the vertical machining center. And it is observed that the more it is processed, the more the fluid type long chip is changed into the powdered chip.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.15-21
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• 2004

Composite materials are widely used to make all kinds of machine parts, internal and structural materials of cars, aerospace industries, building structures, ship materials, sporting goods and others. It is worth the while to use composite materials as various substitutions when compared with others. But the use is limited in the field of the mechanical processing because of its difficulties in processing. Thus, it is proved that the surface is rough in and out of the hole processing the GFRP with HSS drill in the vertical machining center.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.63-68
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• 2008

Hard and brittle materials, such as Ni- and Ti-based alloys, glass, and ceramics, are very useful in aerospace, marine, electronics, and high-temperature applications because of their extremely versatile mechanical and chemical properties. One Ni-based alloy, Inconel 718, is a precipitation-hardenable material designed with exceptionally high yield strength, ultimate tensile strength, elastic modulus, and corrosion resistance with outstanding weldability and excellent creep-rupture properties at moderately high temperatures. However, conventional machining of this alloy presents a challenge to industry. Ultrasonic vibration cutting (UVC) has recently been used to cut this difficult-to-machine material and obtain a high quality surface finish. This paper describes an experimental study of the UVC parameters for Inconel 718, including the cutting force components, tool wear, chip formation, and surface roughness over a range of cutting conditions. A comparison was also made between conventional turning (CT) and UVC using scanning electron microscopy observations of tool wear. The tool wear measured during UVC at low cutting speeds was lower than CT. UVC resulted in better surface finishes compared to CT under the same cutting conditions. Therefore, UVC performed better than CT at low cutting speeds for all measures compared.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.585-590
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• 2002

Abrasive water-jet(AWJ) machining is a new cutting technology. The AWJ can cut various materials touch as metal, glass and stone. However, the AWJ machining makes troubles including kerf, rounding and side taper. In this study, we investigated the correlation between parameters of abrasive water-jet machining arid cutting characteristics. The machining parameter were the material thickness and the traverse speed. The experiment was conducted to cut the stainless steel(STS41) and the mild steel(SS41) specimens. The results of the experiment weirs presented as the relation between cutting conditions and trouble of a dimension error, a conner error, an uncut width and a kerf.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1028-1032
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• 1995

This paper describes the manufacture of spherical and aspherical surface on glass, superalloy and ceramic components. The rotationally symmetricallenses, and the ceramic or superalloy molds with spherical shapes are mainly generated by cutting processes on CNC lathe machine or 4,5 axis CNC machining centers. Recently, spherical shape parts require more precise and efficent machining technologies for wide material range such as optical lens of the lithography device in semiconductor manufacturing processes or the high precision mold machining of anti-chemical, anti-wear materials. In this paper, we introduce a newly developed infeed grinding machine with metal with metal bonded cup type wheel and its effects on spherical surface grinding.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.3
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• pp.1-7
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• 2004

Abrasive water-jet(AWJ) machining can cut various materials such as metal, glass and plastics. However, the AWJ machining has some troubles including kerf, rounding and side taper. In this study, we experimently investigated the correlation between the traverse speed of the abrasive water-jet and the dimensional error of the workpiece according to the thickness and the types of the material. The specimen was the stainless steel and the mild steel and the predetermined contour cutting was conducted. A comer radius error, an uncut width and a kerf were measured and evaluated.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.183-190
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• 2007

It is well known that abrasive waterjet(AWJ) was developed as a kind of high-density energy processing technologies. AWJ is used to obtain the better cutting quality of various materials such as metals, ceramics, glass and composite materials within a short manufacturing time because of the characteristics of heatless and noncontact processing. However, AWJ device still has some problems to obtain the high quality of thin workpiece. In this paper, we investigated the optimal microcutting conditions of AWJ, such as maximum pressure, cutting speed and standoff distance of thin multi-layered materials. The experimental results show that AWJ has possibilities and potential to apply to the microcutting of thin multi-layered materials for IT industrial applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.41-41
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• 2010

In this research, to study tungsten carbide alloy(Co 0.5%) ultra precision turning possibility that is used Glass Molding Press(GMP) using conventional (Rake angle $-25^{\circ}$) single crystal diamond bite observed machining surface condition, surface roughness($R_a$), diamond bite cutting edge after tungsten carbide alloy ultra precision turning. Suggested and designed optimum chamfer bite shape to suggest ultra precision optimum bite using Finite Element Analysis(FEM). After machining tungsten carbide alloy ultra precision turning using optimum chamfer bite and comparing with conventional bite machine result and studied optimum chamfer bite design inspection and also tungsten carbide ultra precision turning possibility for high temperature compression glass lens molding.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.831-836
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• 2000

During machining, since more than 50% compliance of the cutting point in machine tool structures comes from headstocks, with the remainder coming from beds, slides and structural joints, the structural analysis of the headstock is very important to improve the static and dynamic performances. Especially, in case of machining hard and brittle materials such as glasses and ceramics with the grinding machine, the reinforced headstock with the high damping material is demanded. Since the fiber reinforced composite materials have excellent properties for structures, owing to its high specific modulus, high damping and low thermal expansion, it is expected that the dynamic and thermal characteristics of the headstock will be improved if they are employed as the materials fur headstock. In this paper, the design and the manufacturing methods as well as the static and dynamic characteristics of a steel-composite hybrid headstock were investigated analytically and experimentally to improve the performance of the grinding machine system.