Advances in Abrasive Technology IX

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Authors: Feng Wei Huo, Zhu Ji Jin, Fu Ling Zhao, Ren Ke Kang, Dong Ming Guo
Abstract: Grinding of single crystal silicon may be achieved by two modes of material removal: ductile mode and brittle mode. Knowing of the brittle to ductile transition point at which the grinding process changes from the brittle mode to ductile mode is critically important for the realization of ductile mode grinding. This paper uses a new single grain diamond grinding method developed recently by the authors to investigate the brittle to ductile transition during grinding of single crystal silicon in all around. The results indicate that there exist four stages of brittle to ductile transition as the depth of cut is reduced: firstly, the surface cracks outside the grinding groove disappeared, secondlycracks on the bottom of the groove disappeared, then the lateral cracks ceased in the subsurface region, and finally the median crack is suppressed beneath the grooves. It is not until the depth of cut reaches the last transition point that a crack-free groove can be produced, therefore, the last transition stage is decisive. The critical depth of cut delineating the brittle to ductile transition point derived based on this criterion is 40 nanometers, which is much lower than that based on surface cracks.
Authors: Kiyoshi Suzuki, Tetsutaro Uematsu, Manabu Iwai, Shinichi Ninomiya, Sadao Sano, Takeo Nakagawa
Abstract: A new complex grinding method named Ultrasonic Electrodischarging Grinding Method (US-ED-G in short) is described. In the US-ED-G, ultrasonic grinding and ED grinding are simultaneously carried out on an electrically conductive workpiece with a metal bond grinding wheel. When compared with other complex grinding methods, the US-ED-G is remarkably effective in reducing grinding force a great deal and maintaining grinding ability of a wheel for a long time in efficient grinding of extremely hard-to-grind ceramic materials like TiB2. A stock removal rate of 200mm3/min and a grinding ratio of 110 have been attained by selecting appropriate conditions in US-ED-G of TiB2. A compact and rigid ultrasonic attachment is also described, which was developed as a removable tool for carrying out US grinding and US-ED-grinding on a machining center or a grinding center.
Authors: Bo Zhao, Yan Wu, Feng Jiao, G.F. Gao, Xun Sheng Zhu
Abstract: The grain cutting trace of elliptical spiral in workpiece two-dimensional ultrasonic vibration grinding(WTDUVG) is defined, the reason of machining accuracy improvement by applying two-dimensional ultrasonic vibration is discussed. Adopting two-dimensional ultrasonic composite processing, the influences of grinding depth, worktable velocity, wheel granularity on the surface roughness of Al2O3/ZrO2 ceramic nanocomposites were described. Experimental results of AFM microstructure show that the material removal model in WTDUVG is dominated by ductile flow of material, some crystal refinement, the crush powder and grain pull-out are visible and there is almost no fracture. Furthermore, the surface roughness in WTDUVG with coarse grit is about 30 40% less than that in CG under identical grinding condition; the qualitative analysis of X-diffraction results indicated that the surface phases are composed of α-Al2O3, t-ZrO2 and small quality m-ZrO2, there are amorphous phase in the surface both with and without vibration grinding. M-zirconia phase transitions rule in vibration and conventional grinding was found. Under definitive grinding conditions, the material removal mechanism of inelastic deformation is the principal removal mechanism of Al2O3/ZrO2 ceramic nanocomposites, the grit size of diamond wheel and vibration grinding mode have important influence on material removal mechanism of ceramic nanocomposites.
Authors: Yan Wu, A.G. Sun, Bo Zhao, Xun Sheng Zhu
Abstract: Based on the single abrasive particle motion locus of elliptical spiral in two-dimensional ultrasonic vibration grinding (WTDUVG), the theoretical model representing the material removal rate are deduced and verified, and the reason of high efficiency material removal by applying two-dimensional ultrasonic vibration is analyzed. Finally, experimental researches on material removal rate of ceramics were carried out using coarse grit diamond wheel both with and without workpiece two-dimensional ultrasonic vibration assistance grinding. Experimental results indicated that (1) Material removal rate (MRR) in vibration grinding process is about 1.5 times as large as that of in conventional grinding, the experimental results are in good agreement with the calculated ones. (2)The material removal rate increases along with increases of the grinding depth and workpiece velocity both in with and without vibration grinding. (3)The vibration grinding surface had no spur and build-up edge and its surface roughness was smaller than CG significantly. Surface quality of WTDUVG is superior to that of conventional grinding, it is easy for ultrasonic vibration grinding that material removal mechanism is ductile regime grinding.
Authors: Hiroshi Matsuura, Yasuhiro Kunieda, Nobuhito Yoshihara, Ji Wang Yan, Tsunemoto Kuriyagawa
Abstract: A completely new diamond wheel, named the 3R wheel, has been developed. The 3R wheel has three unprecedented functions, reconfiguration, restoration and recyclability, and is molded from a mixture of special thermoplastic resin filler and diamond powder. The concept of the 3R wheel is to control the quantity and the position of abrasive material by actively using heat. In this study, tungsten carbide (WC) was ground using a thermoplastic resin bonded diamond wheels (radius 1.4 mm) with three different concentrations of 1500 grain size abrasive. As a result, a grinding ratio of over 200 and 18 nmRa roughness was achieved without dressing. In addition, a large quantity of abrasives was confirmed on the wheel surface by observation.
Authors: Nobuhito Yoshihara, Ji Wang Yan, Tsunemoto Kuriyagawa
Abstract: Aspherical surfaces are an important technology in optical instruments. Until now, only improvements in form accuracy and surface roughness of aspherical surfaces have been investigated. However, when the surface roughness becomes low, the small waviness of the surface becomes marked. This small waviness is termed “Nano-topography.” Nano-topography causes grinding marks and reduces the accuracy of an optical instrument. Nano-topography is caused by the vibration of a grinding wheel during the manufacture of the surface. This paper will reveal how a rubber-bonded grinding wheel has been developed to absorb that vibration. The dressing of the grinding wheel was also investigated. As a result, it is possible to eliminate the generation of nano-topography.
Authors: Kiyoshi Suzuki, Danyang Zhang, Yoichi Shiraishi, Manabu Iwai, Tetsutaro Uematsu, Shinichi Ninomiya, Sadao Sano
Abstract: This paper proposes a new PCD (polycrystalline diamond) wheel with porous skeleton structure realized by removing the cobalt binder from PCD by EDM (electrodischarge machining), and investigates the grinding characteristics of the wheel. The pores are made successfully on PCD by adopting appropriate EDM conditions. The efficiency of making the pores is found to be higher, when the size of the diamond grains in the PCD material is small, and jumping motion to the copper electrode is not given during the EDM. A porous PCD grinding wheel made by this method using a rotating circular PCD (grain size of 10'm) disc of 20mm diameter has a good skeleton structure with sufficient projections on the wheel surface. A satisfactory grinding characteristics with a surface finish of Ra=0.02'm in grinding on a tungsten carbide work is achieved.
Authors: Manabu Iwai, Kiyotaka Nakagawa, Tetsutaro Uematsu, Keizo Takeuchi, Kiyoshi Suzuki
Abstract: Metal and resin bonded diamond wheels were trial manufactured from boron doped diamond grits possessing electrical conductivity and high oxidation temperature. From the results of the investigation on the electro-discharge truing performance, a high truing efficiency along with the possibility of formation of cutting edges on the grits was confirmed. According to the results of the grinding experiment performed using this grinding wheel with flattened abrasive tips, a remarkable improvement in the work surface roughness could be achieved. Furthermore, from the results of the grinding test on cemented carbide and optical glass using the boron doped diamond grits wheel, the grinding ratio was found to increase significantly, whereas the surface roughness improved compared to a conventional diamond grits (similar friability) wheel.
Authors: T.R.A. Pearce, D.C. Fricker, A. Speight
Abstract: Electroplated CBN grinding wheels are not normally trued on a grinding machine and therefore inherently have a degree of run-out. The effect of run-out on workpiece roundness has both been modelled and measured experimentally. As well as affecting roundness, run-out can result in intermittent grinding around the wheel periphery, which can then lead to preferential wear on the most eccentric part of the wheel. This intermittent effect has been investigated by modelling the variation of the normal grinding force around the wheel and by measuring the variation of acoustic emission around the wheel during grinding tests.
Authors: Wei Peng, C.Y. Yao, Xun Lv, F.Q. Liu, Tao Gao, Ju Long Yuan
Abstract: This paper describes a method for experimental development of a novel fixed abrasive nano-grinding plate (FAG-plate) which is proposed for lapping some rigid brittle materials, such as quartz crystal and silicon. The FAG plate is developed with ultraviolet-cured resin by rapid prototyping technology. The analysis shows that such FAG-plate can keep its grinding ability constant and continuous and it can make the roughness of machined surface reach to nanometer level. Based on experimental comparisons with conventional free abrasive slurry lapping plates, the lapping process using FAG-plate has several distinct advantages. One is that the machining efficiency is significantly improved. The second is that it improves the surface roughness of machined work-pieces, although it decreases the flatness tolerance of materials. Furthermore, the fixed abrasive nano-grinding plate is made by the new bonding materials- ultraviolet curing resin and thus the fabrication of FAG-plate is convenient and economical.

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