Advanced Materials Research Vols. 76-78

Abstract: A new system for measuring a tangential grinding force using the slip of the rotational speed of an induction motor was developed. The motor slip is measured as the change in the rotational period for the induction motor. The system operates LabVIEW software on a personal computer, and a rotary encoder is connected with the motor spindle, which drives the axis of a grinding wheel. A signal of one pulse per rotation from the rotary encoder is input to the interface of the computer to measure the rotational period. LabVIEW has the flexibility of a programming language and operates within a graphic environment in compiling the signal, analyzing measurements, and displaying analysis results. Thus, the present system is simpler than previous development tools. This work conducts a grinding experiment using the developed system to verify the sensitivity and response in measuring the motor slip. As an example of application, semidry grinding is investigated by measuring tangential grinding forces. Hence, we demonstrate the effectiveness of the developed system for data processing in the analysis of grinding phenomena.

Abstract: The boundary layer of air rotating with the grinding wheel can result in fluid starvation in the contact region. The boundary layer acts a barrier to fluid penetration and prevents fluid reaching the contact region and the fluid is deflected elsewhere. Such a situation is inefficient and wasteful. This work reports on an investigation of the air boundary layer aimed at increasing understanding of boundary layer for development of improved fluid delivery systems. The work reported focuses on the outcomes of experimental tests using the Laser Doppler Anemometry technique. Three velocity components of the air flow around the periphery of a rotating grinding wheel were measured for a range of wheel speeds. The contour distribution of the velocity and the turbulent distribution of velocity clearly show the air flow motion around the grinding wheel.

Abstract: In many grinding applications, the material removal rate (MRR) is constrained by undesired thermal surface damages like burns and tensile residual stresses as well as dimensional inaccuracy. In dry grinding, due to lack of coolant, the limitation to achieve higher MRR is more critical as the major part of the heat, generated on the contact zone, is transferred to the workpiece. That is why the lower heat generation is a most important target by dry grinding. This paper presents some of the very interesting results by a comparison between a structured electroplated CBN wheel and a conventional one during surface grinding of steel. One of the grinding wheels has the normal structure and the other has special macro-structure topography developed for dry grinding. The results show a considerable reduction in grinding forces and less thermal damages using the novel electroplated CBN wheel comparing to conventional wheel.

Abstract: The wear of a brazed diamond wheel with diamond grits covered with brazing alloy was investigated in comparison with a traditional brazed wheel whose grits were without covering. The two wheels were brazed in vacuum furnace and grits on one of them were overlaid with a thin layer of brazing alloy. The wear of the two wheels was tested through grinding of granite, during which grinding forces were measured and the wear states of diamond grits were observed. It is shown that grits covered with brazing alloy exhibited stronger self-sharpening ability and fracture resistance. Therefore, the wheel with covered diamonds performed lower grinding force and better wear performance.

Abstract: In order to dominate the wetting behavior of molten Ag-Cu-Ti alloy and control the brazing reaction at the joining interface, CBN abrasive grains were brazed using the composite filler of Ag-Cu-Ti alloy and 8 wt.% TiB2 particles. Ag-Cu-Ti alloy without reinforcing particles was also applied in the current investigation to compare with the composite filler. The characteristics of the joining interface and the reaction products were examined using optical microscope, scanning electron microscope, and X-ray diffraction instruments. Finally, the morphology of the CBN grains on the working surface of the brazed abrasive tools was observed. Results obtained show that the composite filler containing TiB2 particles distribute uniformly in the filler layer. Moreover, the interfacial chemical reaction of CBN grains and Ag-Cu-Ti alloy is restrained when TiB2 particles are added. The sharp edges of CBN grains are exposed fully due to the decreased wetting behavior of the composite filler.

Abstract: Usually, the contact stiffness between a grinding wheel and a workpiece has been measured in a stationary state. So, in this study, the contact stiffness under the grinding operation is measured under different table feed rate of the workpiece. From this result, it is known that, while the contact stiffness in the stationary state increases with the increase of the contact force, the contact stiffness under the grinding operation decreases with the increase of the normal grinding force relating the table feed rate. In this paper, since the number of contacting abrasive grain with workpiece is constant irrespective of the table feed rate, and the residual stock removal of workpiece is varied by the table feed rate, it is clarified that the contact stiffness under the grinding operation differs from the contact stiffness measured by the stationary state.

Abstract: To manage and control grinding process theoretically, the cutting-edge density should be quantified. In this study, the estimation method of the grain-height distribution, which is necessary to quantify the cutting-edge density, has been examined. From the results of simulation by modeling the grain distribution of a grinding wheel, the close correlation has been confirmed between the grain-height distribution and the peak-height distribution of the working surface profile. Based on this, the grain-height distribution can be estimated from the peak-height distribution by narrowing the width accompanied maintaining the total frequency. Since the estimated grain-height distribution agreed well to the distribution determined from the measured 3D-topography, the validity of the method has been confirmed.

Abstract: In this study, the quantification method of the cutting-edge density is proposed because of its close relation to the grinding mechanism. The cutting-edge density depends upon not only the grain distribution but also the thickness of effective cutting-edge layer. Therefore, the quantification of the cutting-edge density requires measuring not only the profile but also the grinding force. The thickness of effective cutting-edge layer can be determined based on the grain distribution, the grinding force and the stiffness of a grinding wheel. From applied result of the proposed method for the actual grinding process, the cutting-edge density and the effective cutting-edges layer is determined appropriately corresponding to the change in the working surface condition.

Abstract: Dressing force measuring equipment was developed and the performance of a single-point diamond dresser was examined focusing on the relationship between dressing force and grinding performance. It was found that a distinct relationship exists between dressing force and grinding performance, and that the sharp-edged single-point diamond dresser can control grinding performance with low dressing force. The single-point diamond dresser and multipoint diamond rotary dresser induce the same dressing force if their wear widths are equal.

Abstract: The efficiency of using of CBN grinding wheels highly depends on the dressing process as well as on the coolant lubricant used. The Institute of Grinding and Precision Technology (KSF) investigated the performance of vitrified CBN grinding wheels -being dressed using different parameters- while using two different grinding oils and two different water-miscible coolant lubricants. The obtained results show that the performance of the vitrified CBN grinding wheels regarding the quality of the workpiece surface, the grinding forces as well as the wear of the grinding wheel, highly depend on the dressing conditions and the type of the coolant lubricant used. Compared to the water-miscible coolant lubricants, the grinding oils show better results.