Tadaaki Hanaoka

Effect of grinding parameters on acoustic emission signals while grinding ceramics

Abstract Grinding process of engineering ceramics is always accompanied by cracking. For automation of machining process it is necessary that a reliable sensing system be devised to detect the workpiece cracking during grinding. In this paper an acoustic emission (AE) sensor was examined for in-process detection of workpiece conditions. Different grinding conditions were performed for evaluation of sensitivity of AE and understanding the effect of each grinding parameter on AE activities during grinding process of alumina ceramics. The results of experiments indicate that AE activities increase with increasing wheel depth of cut and table speed, however when the wheel speed increases, AE activities decrease. As a result, it is shown that AE is basically a function of abrasive grain depth of cut which is in turn, the main factor for determining the surface integrity of fine ceramics.

Acoustic Emission Characteristics in Multipoint Scratching of Fine Ceramics

Using acoustic emission (AE) signal analysis for in-process monitoring of grinding damage in ceramic workpieces requires understanding the characteristics of AE signal during abrading in a free-of-noise environment. In this work multipoint scratching tests were performed using segments of different diamond grinding belts as a model for the grinding process and AE signals were detected and analyzed. Microscopic observations of surfaces and chips were used for understanding the mechanism of material removal and for evaluation of AE data. These observations confirm that the removal mode is a mixture of plastic deformation and fracture. As a result, AE activities were found to be highly sensitive to the material removal mode and phenomena such as the abrasive belt performance, adhesive force and elasticity of the bond, sinking of abrasive grains into the bond, and wear and abrasive separation from the bond.

Whirling action of drill at the beginning of cutting

Abstract In order to measuring the whirling phenomenon of drill, we have designed new measuring apparatus. The distinction of this apparatus is that a workpiece could be moved freely in the plane of right angle to drill by whirling action. To detect the behavior of workpiece, whirling phenomenon could be measured. As the result, it was found that the whirling characteristics are closely related to the geometrical error of drill.

Estimations of Finishing Performance of Lapping Films Based on Deformation Analysis of their Constituents. Finishing of Ceramics by Diamond Lapping Films.

This paper describes the finishing performance of lapping films based on deformation analysis of their constituents by using the Finite Element Method (FEM). The models applied to the FEM were varied by changing polyester film backing thickness, bond thickness, shape of abrasive grain and size of grain of lapping film, supposing that different types of lapping films are used in the actual finishing processes. And, the effects of them and the elastic characteristics of bond on the deformation characteristics were also estimated. As a result, the behavior of abrasive grains in the contact area between the lapping film and workpiece became clear. Furthermore, experiments on the cylindrical ceramic workpiece surface finishing, utilizing lapping films coated diamond abrasive grains, were carried out and the effects of finishing conditions on stock removal and finished surface roughness were examined. From the experimental results, it was confirmed that the experimental characteristics could be explained clearly by the obtained results of FEM analysis.

Finishing Characteristics of Lapping Films.

Lapping films are widely applied to the finishing processes. There are, however, a few research works on the machining characteristics of lapping films. In this study, finishing of cylindrical workpiece surfaces were carried out with measuring the grinding force, stock removal and finished surface roughness in order to examine the machining mechanism. Furthermore, the elastic contact conditions of contact roll, lapping film and workpiece were estimated by using the Finite Element Method (FEM). As a result, the effects of grinding conditions on the stock removal and finished surface roughness became clear and the behavior of grains in the contact area between lapping film and workpiece were also examined.

Finishing of Cylindrical Surfaces by Using Lapping Films.

Many types of lapping films are manufactured today. This is because they greatly improve the finishing process and reduce the finishing costs. However, the effects of the structural characteristics of lapping films and the elastic contact conditions between contact roll and workpiece on the performance of finishing have not yet been fully explained. In this study, finishing of cylindrical workpiece surfaces were carried out with different contact pressures applied to the workpiece surfaces and with rubber contact rolls of different hardness, using lapping films of different backing thickness and grain sizes. As a result, the effects of them on the finished surface roughness, the ground amount and the accuracy of their forms were clearly recognized. And useful suggestions were obtained for implementing the lapping film finishing effectively.

Influence of the height distribution and elastic displacement of the grain cutting edges on the ground surface in abrasive belt grinding.

A simulation of abrasive belt grinding process was carried out. In abrasive belt grinding, the height distribution of grain cutting edges changes with the advance of grinding time and the elastic deformation of contact wheel is the cause of the displacement of grain cutting edge position. So, the influence of the height distribution and elastic displacement of the grain cutting edges were investigated by the simulation. As a result of that, the mechanism of residual depth of cut and the finished surface roughness were analyzed theoretically in cylindrical plunge grinding. The obtained main results are as follows. (1) Residual depth of cut and finished surface roughness increase as the height distribution of grain cutting edges becomes wide. (2) In the case of using a rubber contact wheel, the displacement of grain cutting edges makes the residual depth of cut increased. But, the increase of effective cutting edges makes the finished surface roughness improved. (3) Residual depth of cut caused by the height distribution and displacement of the grain cutting edges is almost generated at the start of grinding. (4) It was found that there is an optimum rubber hardness of contact wheel.