Abstract: This paper aims to develop an alternative novel technique for the high efficiency and ultrafine surface finishing of fused silica glass. A semi-fixed abrasive tool named MCF (magnetic compound fluid) wheel is produced by distributing a certain volume of MCF slurry uniformly over the whole circumference surface of ring-shaped permanent magnets. An experimental rig is constructed in house followed by experimental investigations involving effects of the MCF wheel construction and process parameters on the material removal and work-surface roughness. As a result, the performance of the developed MCF wheel in the surface finishing of fused silica glass has been confirmed, and the appropriate wheel construction and process parameters have been determined in terms of the material removal rate, the flatness of polishing area and the surface roughness, showing an extremely smooth work-surface with surface roughness of Ra0.92nm has been achieved successfully in the current work.
Abstract: Soft magnetic powder cores are materials manufactured by pressing pure iron powder covered with insulating film into shape. These are widely known soft magnetic materials which are used as essential electromagnetic conversion parts in automobiles and household appliances. In recent years, demand for higher magnetic properties and dimensional precision has been growing with respect to soft magnetic powder cores. It has therefore become necessary to develop a high-efficiency, high-precision finishing method. The issues to be addressed with regard to this kind of method are: (1) the pure iron used in these materials displays ductility resulting in burring and cohesion to machining tools, (2) these materials are green compacts with low binding forces between powder particles and high tendencies towards cracking and gouging, and (3) these materials possess residual pores at levels of several percent thus resulting in microscopically intermittent processing which causes heavy machining tool wear. We have solved these issues through the development of a super-smooth finishing method designed for soft magnetic powder cores.
Abstract: The purpose of this study is to develop the environment-friendly coolant. Cylindrical plunge grinding tests are carried out using alkaline electrolyzed water, high-frequency reduced water and alkali-reduced water as coolant. Most effective coolant is brought out in comparison with surface roughness, grinding force and workpiece surface temperature. Moreover, elemental analyses and measurements of contact angle of treated water are carried out in order to clarify the effect on grinding performance. Furthermore, elemental analyses and observation of evaporation residues in treated water are also carried out. As a result, grinding performance using alkali-reduced water is better than that using alkaline electrolyzed water or high-frequency reduced water.
Abstract: This paper reports our recent results on the diamond grinding process of single crystallized sapphire wafers. It was found that the diamond grains were severely dislodged at the wheel/ workpiece interface and the material was removed by a mixed process of both grinding and lapping. Grinding governed the wafer center while lapping dominated its fringe. By increasing the wheel speed, it was able to shift the dominant process from lapping to grinding, and achieve a better surface roughness. Nine diamond wheels varying in both concentration and bond material were tested in surface grinding of 6 inch sapphire wafer, to investigate the dynamic behavior of diamond grain in the grinding process and its resultant surface quality and productivity.
Abstract: Roughness is important criterion of ground surface. When the surface roughness is demanded to be smooth, it is required to make the grinding conditions optimum. To optimize the grinding conditions, relationship between grinding conditions and ground surface roughness must be known. Therefore, it has been attempted to reveal the effect of grinding conditions on the roughness of ground surface over the years. From previous researches, it becomes possible to estimate the ground surface roughness with statistical grinding theory. However, there are some parameters, such as wheel depth of cut and distribution of abrasive grain, are not factored in the theory. In this paper, fundamental research on cross sectional profile is carried out to consider the relationship between the wheel depth of cut and ground surface roughness.
Abstract: A vitrified bonded diamond wheel having electrical conductivity was manufactured on a trial basis. The electrically conductive (EC) vitrified bonded diamond wheel has enabled an electrodischarge truing and an electrical contact sensing. In this study, the EC vitrified bonded diamond wheel is applied to the EDM (Electro Discharge Machining) assisted grinding of PCD materials. The result shows that a lower and more stable grinding force can be realized and a better surface finish is attained compared with those achievable with a metal bonded diamond wheel.
Abstract: Single-layered metal bond diamond wheels are useful to high efficient grinding of difficult-to-grind materials because of the high gripping force of abrasive grains and the controllable grain density. In this paper, fundamental information are obtained for an application of electrostatic force to setting of diamond grains into pasted metal bond slurry layer on wheel surface, investigating experimentally jumping phenomenon of diamond grains in an electrostatic field between a electrode plate and metal bond slurry layer. The SD grains and the SDC grains coated with Ti are selected. SDC grains jump into a metal bond layer as quick as making an electrostatic field, however SD grains jump with short time lags. The setting rate of SDC grains is larger than that of SD grains, and setting position accuracy of SDC grain array is better than SD grain array. The possibility of setting abrasive grains into single-layered metal bond diamond wheel surface using electrostatic force is obtained and SDC grains are suitable to the proposed abrasive setting method.
Abstract: Fabrication experiments of porous composite-bonded CBN wheels were conducted using alumina (Al2O3) bubbles, CBN grains, Cu-Sn-Ti alloy and graphite particles. Influence of sintering parameters and porosity on the bending strength of the CBN composite blocks was measured and analyzed. Dressing and grinding practice was carried out. The results show that the optimal sintering temperature of the CBN composite blocks is 880°C. When the porosity of composite blocks is 8-45 %, the strength reaches 51-103 MPa. Regular shape of the pores is obtained after dressing. Both the grinding force and grinding temperature of the composite-bonded CBN wheel are lower than that of the vitrified one under the same grinding condition, which indicates the better grinding performance of the new-type porous composite-bonded CBN wheel.
Abstract: In grinding operation, elastic deformations of the grinding machine and the grinding wheel induce a residual stock removal of workpiece. On the other hand, thermal expansions of the workpiece and the grinding wheel increase the depth of cut. Therefore, calculation of a ground depth of cut and/or the grinding time has to be considered by the elastic deformations and the thermal expansions. From such a viewpoint, in this study, grinding process model taking into account the elastic deformations and the thermal expansions was proposed. This paper aims to estimate the grinding time by means of the proposed grinding process model.