A grinding wheel is made of extremely hard abrasive grains that form cutting edges on the wheel in comparison with metallic material, nonmetallic material, etc. The grinding wheel consists of three constituents, namely the abrasive grain, bond and pores. Abrasive grains act as cutting edges for cutting the work material. Bond platform support the cutting edges as a holder. Pores store cutting chips and assist flush out. During use, an abrasive grain that decreases at the cutting edge always provides a new edge, but when it has been exhausted and released, the next abrasive grain is newly provided (this phenomenon is called self-sharpening). A grinding wheel rotates at high speed. Each cutting edge consists of many blades. Thus, one cutting blade cuts the workpiece for a short time and takes a rest for a long time. This is favorable as viewed from standpoint of grinding wheel service life. Since there are the above features for grinding work, a high efficiency, high precision and good finishing surface can be obtained.
The mechanism of workpiece removal in grinding is generally explained under consideration of tribological aspects. Grain depth of cut, average cross-sectional area of grinding chips and average cutting-edge spacing are derived theoretically. The given values,however, are not decisive, but change with wheel wear and three-dimensional distribution of cutting edges. Characteristics of wheel-to-workpiece contact are experimentally examined. Cutting ability of abrasive grains, successive cutting-edge spacing,temperature of wheel-to-workpiece contact zone and grinding forces widely change with wheel ware.
The dimensional accuracy is reduced due to thermal deformation of a ground workpiece during the grinding process. The thermal deformation of the workpiece is caused by grinding heat that is proportional to tangential grinding force. Therefore, to improve the dimensional accuracy of the ground workpiece, it is necessary to understand the thermal deformation of the workpiece during the grinding process. In this article, the mechanism of thermal deformation of a workpiece and effect of the grinding heat are explained. The grinding force is important factor of thermal deformation and size generation of the workpiece in grinding. An advanced compensation system of thermal deformation of the ground workpiece by using the simulation analysis of the thermal deformation is also introduced.
Although super abrasive grinding wheels are now being used frequently, we have considered the basic theory of the dressing for ordinary grinding wheels. At first presenting the basic thinking of dressing for ordinary grinding wheel, then the concept on the method of dressing for super abrasive grinding wheels has been explained. In addition, this report indicates the outline of the highly efficient and accurate SF dressing method developed by the author.
Grind fluid is having important role to produce in processing, low cost with high-efficiency. Recently, the required performance of grinding agents has become highly diversified, and many grinding fluid have been developed. As examples of such fluid, there are fluid for regulations concerning chemical substances, considering environment. Basic knowledge such as the roles and types of fluid are understood to demonstrate the performance of grinding fluid sufficiently, and proper oil solution selection and daily management is important. In this paper we introduce of grind process fundamental, performance and feature of grind fluid,selecting method, instructions for use and recent developments.
Productivity can be improved, if a mirror finished surface is obtained with grinding instead of polishing. The quality of the surfaces, finished with conventional grinding wheels composed of fine abrasives, is worse than the one finished by polishing. In this article, we introduce a new layer-structured grinding wheel, based on a natural whetstone called Awasedo, and a grinding wheel which has product layer of silica and mica. The ability of the grinding wheel is also described in the case of grinding a 3-inch silicon wafer under constant-pressure process. And that gives a mirror surface with the roughness of 1nm Ra and 7nm Rz was obtained.
In this paper, we introduce the friction characteristics and the grinding performance of the grinding wheel containing nanodiamond and show examples of ultra-smooth planar processing and shape processing of materials that are difficult to grind precisely and efficiently. Concretely, 0.01 to 4.9 wt. % nanodiamond aqueous solution showed a low friction coefficient, and grinding wheel containing nanodiamond was effective for improving the surface roughness of various glass, cemented carbide and sapphire. By combining the grinding wheel containing nanodiamond with ELID grinding and ion-shot dressing method, it was possible to obtain the mirror surface of the injection needle using only water. Compared to the current materials, those ground needles have become possible to reduce the puncture resistance.
In the cross roller bearing, rollers are arranged crosswise with each roller perpendicular to the adjacent roller in a V groove. This design allows one bearing to receive loads in all direction. Since the cross roller bearing achieves high rigidity despite the minimum dimensions of the inner and outer rings, it is optimal for applications such as the joints of industrial robots, swiveling tables of machining centers and medical equipment. Although the cross roller bearing has high rigidity, friction torque is said to be high compared to other bearings. Studies of the friction torque of the cross roller bearing have hardly been published. In the cross roller bearing, it is said that preload affects friction torque, but preload measurement method of the cross roller bearing has also not been studied. In this study, the authors measure preload of the cross roller bearing with a newly developed method, and the relationship between tightening torque and preload was clarified. Furthermore, experiments on the influence of preload and grease components on friction torque were carried out. The results showed that, the influence of preload is small and the influence of kinematic viscosity of grease base oil is large.
In elastohydrodynamic lubrication (EHL) theory published in 1962, Dowson et al. derived a density pressure relational equation. Therefore, it seemed that this equation could be utilized as an estimation equation of the density term of the viscosity pressure-temperature-density linear equation of the 1st report. However, since the temperature function is not included in the equation, the calculated value at 40°C is in good agreement with the measured value, but in the high temperature region, the calculated value found large deviation from the measured value. Therefore, introduction of temperature function into the equation was studied, and density-pressure-temperature relational equation was newly derived. In this result, it became possible to estimate the high pressure density at each temperature, and it became possible to utilize as the estimation equation of the density term of the 1st report. And it was found that the linear equation can also be applied to the ASME report data up to around 1 GPa. Incidentally, the slope a of the linear equation is a characteristic constant of the lubricant related to the high pressure density and the 1+1/b value obtained from the intercept b indicates the maximum density ratio.
To decrease the agitating resistance and the rolling viscosity resistance of rolling bearings, it is effective to reduce the quantity of lubricant. However, the reduction of lubricant quantity decreases the EHL oil film thickness. The breakdown of EHL oil film causes the short life of the rolling bearing. In this paper, we used three-wavelength interferometry method to obtain basic data for the development of new surface textures for operation under starved lubrication conditions. The three-wavelength interferometry method is successfully applied for the measurement of EHL oil film thickness on the textured surface under rolling contact. With this method, measurements can be taken with high precision over wide thickness range and in one shot. Three texture patterns were tested under fully flooded lubrication: line groove, cross-hatch and dimples. Under fully flooded lubrication, oil film on the edge near the groove became thinner with line groove and cross-hatch textures, but did not change significantly with dimple texture. Under oil starvation, cross-hatch and dimple textures were compared. The oil film did not change significantly with both of them. By increasing the dimple diameter and deepening the dimple under oil starvation, the amount of oil retained increases and the oil film also thickness increases.
Machine elements in rolling contact operate under severe loading condition associated with repetitive pure rolling or rolling/sliding contacts. Such a severe loading condition can promote fatigue accumulation in the surface and subsurface layers leading to a fatigue flaking failure known as rolling fatigue. In our previous report, a novel test rig to simulate flaking of constant velocity universal joints, CVJs, was developed and preliminary tests using this test rig showed that various modes of failures can occur in CVJs depending on the test condition. This study is to evaluate flaking prevention of greases using this test rig under a test condition in which flaking is caused by the development of subsurface comb-shaped cracks. The results confirmed that the occurrence of the flaking is significantly affected by the type of thickener used. The flaking and cracks were initiated at the stroke end at a relatively low speed suggesting that the thickener contributes to extended flaking life by thickening a boundary film in the low-speed range.