Advanced Materials Research Vol. 1017

Abstract: In order to decrease the negative environmental impacts of the cutting fluids (for example, disposal of grinding sludge) and also to reduce the manufacturing costs and the required space for the machines the dry grinding can be a conceivable alternative for the conventional grinding processes. Nevertheless, dry grinding has not been widely introduced into industry because of the high temperature generated in the grinding zone and difficulties of heat transfer without coolants. Selection of the proper grinding wheel bonds, grit sizes and concentration has significant effect on the grinding performance and the generated heat in the contact zone. This paper addresses the effects of the grinding wheel bond and the concentration on the dry grinding process efficiency through comparing the results of the carried out experiments with three resin bonded cBN-cup-wheels, each consisting different bond components. For this purpose, surface roughness and thermal damages during dry and wet grinding (utilizing grinding oil) by three different resin bonds were measured. The results show almost identical surface roughness values for dry and wet grinding. Furthermore, using the resin-kryolith-graphite bonded wheel leads to a reduction in thermal damages on the workpiece. Through different experiments, it was shown that the different bonds, used in this study, have significant influence on the chip loading of the grinding wheels. This is contributed to the different chip formation mechanisms and induced grinding temperatures when grinding by the different wheel bonds.

Abstract: A grinding wheel wears rapidly during ultrasonic assisted surface generation of a large aperture aspherical RB-SiC mirror, which leads to an increase of grinding force and profile error. In this paper, different types of resinoid bonded diamond grinding wheel with a same grit size were dressed with high-pressure abrasive water jet. The dressing effects of abrasive water jet were assessed through comparing the 3D roughness of the grinding wheel topographies before and after dressing. The experimental results show that diamond grits of a worn grinding wheel are protruding from bond after dressing. The feed rate of nozzle and the bond materials have significant impact on the 3D surface roughness of the wheel and dressing efficient. The softer binder and the decrease of the feed rates and lead to deeper grooves during dressing of grinding wheel. However, too low feed rate will make a large number of abrasive particles drop from binder, which worsens the wheel topography. Therefore, to dress grinding wheel well and efficiently, optimized feed rate must be chosen.

Abstract: The possibility of using the new processing technique of vacuum evaporative pattern casting (V-EPC) process to fabricate the Al-Si based bonded diamond grinding wheels was explored in this paper. Distribution of diamond grits in the diamond/EPS composite pattern and in the grinding layer of the cast of the grinding wheel were analyzed. Microstructures and mechanical properties of the metal bonds and diamond composites fabricated by V-EPC process were studied. It is confirmed that thermal damage of the diamond grits did not occur. Strong bonding between metal bond and diamond grits can be produced. However, the uniformity of the distribution of diamond grits in the metal matrix should be further improved. Also, further hardening on the metal bond is necessity by trying other kinds of aluminum alloys.

Abstract: The wafer grinding by use of fixed abrasive diamond wheels is required to create a high-quality wafer surface in a short time. In general, it is known that the grinding performance of diamond wheel is mainly dependent on grinding wheel specifications and grinding conditions. The cutting edge distribution or abrasive protrusion height in depth-wise of a specified wheel is one of the most important factors to determine the finishing surface roughness and the grinding force, which in turn determine the surface and subsurface quality of ground wafers. The overall purpose of this study is to understand the dynamic behavior of each diamond abrasive via modeling an actual diamond wheel and simulating of wafer grinding. In previous report [1], we have theoretically analyzed three-dimensional cutting edge distribution on the working surface of diamond wheels. This paper reports our recent achievements in the evaluation of 3-D cutting edge distribution in depth-wise of a specified wheel via the bearing ratio of its topography.

Abstract: This paper describes on the experimental results of diamond wheel wear in groove grinding of cemented carbide. The speed ratio of grinding was widely changed. Square grooves and 90 degree V-grooves were ground. The square grooves were ground by using a resin-bonded diamond wheel and the V-grooves were by a vitrified diamond wheel. At first, a water-based coolant was used, but afterward, to investigate a possibility of nitrogen to suppress the wear of wheel, nitrogen gas was dissolved into the water-based coolant. The main results obtained are as follows, (1) The wheel wear increases as the speed ratio decreases, (2) The average grinding forces is almost independent from the grinding conditions but those at the lowest speed ratio are fairly large, (3) The influence of nitrogen gas dissolved coolant is small, but in a case of V-shape grinding at a middle speed ratio there found a considerable decrease of wheel wear.

Abstract: This study was examined about the relationship between the fillers added to the grain layer of a resinoid bond diamond wheel and mechanical properties, the grade, the grinding performance. In the abrasion test using a constant pressure grinding, it was shown clearly that the critical grain holding power changed by kinds of fillers. On the other hand, in the constant cut surface grinding, the grinding interval was evaluated based on the grinding force. And, it was confirmed that the grinding interval changed by kinds of filler. Also, it was found that the characteristics of truing and dressing changed by kinds of filler. In addition, Young's modulus and bending strength of the grain layer of a resinoid bond diamond wheel was measured by three point bending test and ultrasonic pulse method. In the results, it checked that the mechanical properties such as bending strength and Young's modulus of a grain layer changed by kinds of filler. And, the modulus of rupture was calculated from the Young's modulus and bending strength.The result of having compared the modulus of rupture with the critical grain holding power, it was found that the modulus of rupture and the critical grain holding power have good correlation. Namely, the critical grain holding power of a resinoid bond diamond wheel can be evaluated by the modulus of rupture. Furthermore, it was shown that the grinding performance may be able to be predicted by the modulus of rupture of a grain layer of a resinoid bond diamond wheel.

Abstract: This paper presents the results of an experimental investigation on molar ratios of MgO/ MgCl₂ affecting the hardness of magnesia grinding wheels, which is one of the most important properties. Magnesite grinding blocks of different ratios of MgO/MgCl₂ were prepared. The surface Rockwell hardness of which was tested under the same curing conditions. By an integrated assessment of the experimental studies of hardness and component, it is recognized that the molar ratios of MgO/MgCl₂ can significantly affect the properties of magnesia grinding wheels. With the increase of MgO/MgCl₂ molar ratio, hardness of the specimens increases. Scanning electron microscopy (SEM) studies on grinding blocks of different ratios indicated that micro needle shaped crystal structure of phase 5 are mainly responsible for hardness development. Finally the optimal recipe was selected in consideration of the characteristics of the silicon mechanical chemical grinding (MCG), which was verified to be effective by the following grinding experiment.

Abstract: Currently CAD/CAM systems have become more and more common in automated manufacturing to enhance the accuracy and efficiency of machining process. On the other hand, 3D model processing technologies has long been researched in computer graphics (CG) fields. However, few algorithms were designed for the application of machining and manufacturing. In this paper, the current researches about the 3D model processing technologies in the application of freeform surface machining were introduced. These researches take the advantage of 3D model processing technology, and focus on the application of machining and manufacturing. They provide a new methodology to enhance the intelligence of the CAM, and improve the integration of CAD and CAM.

Abstract: C-ring specimen experiment was conducted combined with finite element method, in order to reveal the influence of residual stress on corrosion resistance of machined surface. The results show that pitting is the main corrosion type in marine water under stresses. Under compressive stresses, the distribution and expansion of corrosion pits extend along radial direction of C-ring. The corrosion depth and corrosion area ratio show that corrosion extent decreases with the increase of compressive stress. Finally, the results can be used to optimize cutting parameters.

Abstract: The local distribution of the convection heat transfer coefficient (CHTC) of grinding fluids along the wheel-work contact zone under high speed grinding conditions has been investigated. A new approach has been proposed to derive the distribution of CHTCs along the contact zone by using the measured grinding temperatures and linking the distribution of local heat flux and heat partitioning to the workpiece, wheel and grinding chips. It has been found that the worktable speed is the key factor affecting the pattern of CHTC distribution, whilst the grinding speed strongly affects the overall magnitudes of the CHTCs. Down grinding mode is beneficial for achieving effective cooling under creep-feed conditions. The distribution of CHTC under faster worktable speeds shows a rather different pattern, which has to be considered when selecting the grinding mode and grinding fluid supply strategy.Keywords: Grinding, Fluid, Convective heat transfer coefficients, Temperature, High speed