Papers by Keyword: Optical Glass

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Authors: Jian Qiang Guo, Hitoshi Ohmori, Wei Min Lin, T. Adachi, H.M. Shimizu
Abstract: In order to improve the application of neutron scattering technique, a new neutron optical device, which optical system consists of an array of several ten neutron Fresnel lenses, is designed by the researcher engaging in the study of neutron optics. Neutron Fresnel lenses for this new device have the same symmetric concave form. Its center is a spherical surface and the other surfaces are conic section. MgF2 single crystal glass is selected as the material for making neutron Fresnel lens because of its high transparence. Considering the form complicity and the brittle properties of MgF2 material, the fabrication of neutron Fresnel lens is of very difficulty. Form ELID (electrolytic in-process dressing) grinding was used for grinding the neutron Fresnel lens in this first study. The optima of grinding conditions for #325, #1200 and #4000 cobalt bonding diamond abrasive wheels are obtained through a series of tests. The MgF2 material is removed at the ductile mode by using #4000 abrasive wheel. Thus, the neutron Fresnel lens fabricated has low roughness and high transparence. The transmission of an array of 50 pieces of neutron Fresnel lens is 92.5 percents to neutron beam with wavelength 5Å and 79.3 percents to 16Å.
904
Authors: Ai Bing Yu, A.J. Wang, C.G. Luan, S.F. Chen
Abstract: Bonds of electroplated diamond tools are investigated through the studies of microstructures and properties. Three coatings for tool bonds, nickel, nickel-cobalt and bright nickel, were fabricated with electrodeposition processes, and were heat-treated with different temperatures. The hardness and microstructures of coatings were measured and observed. Optical glass K9 was machined with fabricated electroplated diamond tools to compare material removal rate and grinding ratio. The grain sizes of three bond coatings are different. The laminar structures of nickel-cobalt and bright nickel coatings turn to fine columnar structure after heat treatment processes. With heat treatment of 200°C temperature, bright nickel electroplated diamond tool presents highest values of material removal rate and grinding ratio. The research results show that better microstructures and property of bond for electroplated diamond tool can be obtained by selecting proper electroplating technology and heat treatment processes.
81
Authors: Assefa Asmare Tsegaw, Fang Jung Shiou
Abstract: As the needs of optical glasses are on the rise, the precision on shape, form, surface qualities and the scaling down of sizes are rising, too. The standards and surface finish of reference mirrors used in measuring appliances are crucial; hence, enhancement of the surface finish is indispensable in manufacturing industries. This paper proposes a self-propelled multi jet polishing technique for ultra precision polishing process in which bladeless Tesla turbine was used as a prime mover. The turbine is characterized by high swirling velocity at the outlet; therefore, high kinetic energy in the course of away from the turbine was used as polishing energy. Simulation of the flow of the field of turbine blades using computational fluid dynamics software (CFD) has also been presented. With a newly designed and manufactured polishing tool, this paper investigates the optimal polishing parameters for surface roughness improvement of crown optical glasses using Taguchis experimental approach; signal-to-nose (S/N) ratio and ANOVA analysis was also carried out to determine the effect of main factors on the surface roughness. Consequently, a 2.5μm size of Al2O3 abrasive, 10wt% abrasive concentration, 80rpm of polishing head, 6 numbers of nozzles, 6 kg/cm2 of pressure, and 45min. of polishing time have been found to be the optimal parameters. It was observed that about 94.44% improvements on surface roughness; Ra, from 0.360μm to 0.020μm has been achieved using the optimal parameters. In addition to this; angular speed of polishing head, pressure and polishing time were found to have significant effect on surface roughness improvement.
481
Authors: Assefa Asmare Tsegaw, Fang Jung Shiou
Abstract: Most optical glasses are in recent years being manufactured by diamond turning processes which has certainly modernized the field of production of optics. Confines of diamond turning for both form and surface finish accuracy have not been reached, yet. In advent of contemporary technology, high precision finishing techniques are of great concern and the need of present industrialized-scenario. This paper presents the development of a small rotary multi-jet abrasive fluid jet polishing tool for use in polishing of optical glasses. The newly designed and manufactured tool has relative angular speed with respect to the spindle of machining centre and is capable of polishing at micro levels. The paper also investigates the optimal polishing parameters for selected, crown optical glass based on experiments conducted using Taguchi’s experimental method. According to the possible number of control factors L18 orthogonal array was used. ANOVA analysis was carried out to determine the main factors which would affect the surface roughness significantly. Consequently, a 2.5 μm size of Al2O3 abrasive, 10wt% abrasive concentration, 40 rpm of polishing head rotation, 6 numbers of nozzles, 6 kg/cm2 of fluid pressure, 45minuet of polishing time and 40% of step over have been found to be the optimal parameters. It was observed that about 97.22% improvements on surface roughness; Ra, from 0.360 μm to 0.010 μm has been achieved using the optimal parameters. In addition to this; rotation of polishing head, applied fluid pressure and polishing time were found to have significant effect on surface roughness improvement.
140
Authors: Terutake Hayashi, Masaki Michihata, Yasuhiro Takaya
Abstract: The nondestructive, non-contact, three-dimensional evaluation of optical glass has been important to the manufacturing of high-precision optical components. In order to achieve high-precision nondestructive evaluation of optical heterogeneity, we develop a versatile evaluation system using the parallel phase- shift digital holography, which enables measurements of the optical path differences at a nanometer-scale resolution. The amplitude and phase distributions of the object wave can be reconstructed directly from a single hologram by using the parallel phase-shift digital holography system. The optical heterogeneity of a sample is determined quantitatively based on the distribution of the optical path differences quantitatively.
865
Authors: Peng Jia
Abstract: For the technology of diamond cutting of optical glass, the machinability of glass is poor, which hindering the practical application of this technology. In order to investigate and ameliorate the machinability of glass, and achieve optical parts with the satisfied surface quality and dimensional accuracy, this paper first conducted SF6 indentation experiment by Vickers microhardness instrument, and then the scratching tests with increasing depths of cut were conducted on glass SF6 to evaluate the influence of the cutting fluid properties on the machinability of glass. Based on this, turning tests were carried out, and the surface quality of SF6 was assessed based on the detections of the machined surfaces roughness. Experimental results indicated that compared with the process of dry cutting, the machinability of glass SF6 can be improved by using the cutting fluid.
16
Authors: Qing Liang Zhao, Jun Yun Chen, Jun Yao
Abstract: In this paper, a copper-resin bonded diamond wheel was applied to machine the optical glass on a precision grinder. The process of truing and pre-dressing with ELID (electrolytic in-process dressing) were first carried out for the grinding wheels, then the ELID assisted grinding experiments were conducted with the special fine and coarse grained diamond wheels. The experimental results show that the fine and coarse grained wheels can all generated the smooth surface with the surface roughness in nanometer scale and the coarse grained diamond wheel correlates to the slightly more surface damage than the fine grained diamond wheel, which also proves that the high efficient grinding of the optical glass with a good surface quality can be realized with the coarse grained copper-resin wheel on a precision grinder and the grinding wheels were all well conditioned with the conditioning method presented in this paper.
76
Authors: Xin Yu Liu, Li Fen Hou, Ren Ping Zou
Abstract: The mechanism of ultrasonic assisted grinding is presented. Single factor experiment method was used to conduct experiments in order to reveal the effect of different grinding parameters (including feed rate, spindle speed, grinding depth) on surface roughness and grinding force of optical glass in ultrasonic assisted grinding and conventional grinding. The experiment data wss analyzed and it shows that the surface roughness and tangential grinding force decrease while the axial grinding force increase in ultrasonic assisted grinding process than that in conventional grinding process.
1999
Authors: Hong Hua Su, Jiu Hua Xu, Yu Can Fu, Wen Feng Ding, Shuai Wang
Abstract: The dressing methods of monolayer diamond tool have recently been developed increasingly because a substantial improvement of the ground surface roughness could be achieved with the dressed monolayer diamond tools. In this paper, a new dressing method was proposed, namely chemical-mechanical dressing of the diamond grits. Dressing experiments were carried out on the monolayer brazed diamond grinding wheel. The grit-tip distances from the base of wheel substrate were measured before and after dressing. Grinding experiments were conducted on K9 optical glass after each dressing interval. The roughness parameters of the ground surfaces were measured. The outcome of this attempt appeared highly encouraging, and the dressing of monolayer brazed diamond grinding wheel is effective with the chemical-mechanical dressing.
208
Authors: Peng Jia
Abstract: In diamond cutting of optical glasses, the magnitude of critical depth of cut for brittle-ductile transition is an important factor affecting the machinability of the work material in terms of production rate and surface quality. In this work, scratching tests with increasing depths of cut were conducted on glass BK7 to evaluate the influence of the cutting fluid properties on the critical depth of cut. Boric acid solutions of different concentrations were selected as cutting fluids in the tests. The resulting scratches were examined utilizing a white light interferometer and the values of the critical depth of cut were determined based on the observations of the micro-morphology of the scratch surfaces produced. Experimental results indicated that compared with the process without cutting fluid action, the critical depth of cut in diamond cutting of glass BK7 can be increased by using boric acid solution as the cutting fluid.
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