Papers by Author: Akihiko Kubo

Abstract: This paper presents a surface generation mechanism of grinding that captures the microscopic interaction between the abrasive grains and work-surface. The mechanism utilizes both deterministic and stochastic formulations and deals with such realistic constraints as loss/wear and uneven distribution of abrasive grains, roughness of already-ground work-surface, and machine stiffness. Apart from the theoretical treatments, numerical examples are cited showing how the topography of the work-surface evolves because of the proposed mechanism. The work will help build computerized systems ensuring a reliable prediction of the surface roughness due to grinding under the realistic constraints.

Abstract: A computer-aided simulation was developed to visualize the three-dimensional topography of a grinding wheel surface dressed by a rotary diamond dresser (RDD), and the effects of up-cut and down-cut dressing on the roughness of the dressed surface were examined to demonstrate the effectiveness of the simulation. In the case of single-pass dressing, the roughness of the grinding wheel surface decreased with decreasing dresser feed rate and approached a constant value depending on the velocity ratio of the RDD to the grinding wheel. In the case of multipass dressing, up-cut dressing provided the grinding wheel with a surface topography which was much more stable than that provided by down-cut dressing.

Abstract: Hard materials based on Alumina (AN), Silicon Carbide (SC), Boron Carbide/Nitride (BC/N), Zirconia (ZN), and alike are often used to produce abrasive grains and coat cutting tools. These materials improve the performance of grinding/machining operations by providing an enhanced productivity, a longer grinder/tool life, and a better surface finish. On the other hand, they might leave some burdens on the environment. Therefore, eco-attributes (i.e., energy consumption, CO₂ emission, NO_X/SO_X emission, water usage, recycle fraction, etc.) of these hard materials should be used to make an informed decision. This study deals with this issue and provides an evaluation of AN, SC, BC/N, and ZN based hard materials in terms of CO₂ emission, NO_X emission, SO_X emission, and water usage. The outcomes of this study are useful for analyzing grinding and other abrasive processes for achieving eco-manufacturing.

Abstract: Face cutting of tungsten carbide was conducted using two monocrystalline diamond tools and three polycrystalline diamond tools to investigate the wear characteristics in terms of the crystal structure and composition of the diamond. It was found that the wear of the monocrystalline diamond tool depends on the crystal planes that form the rake face and flank face of the cutting tool, and a cleavage fracture occurs when the cutting force acts as a shear force on the (111) crystal plane. The binderless nano-polycrystalline diamond tool exhibits excellent wear resistance beyond those of the sintered polycrystalline diamond tool and chemical vapour deposition polycrystalline diamond tool, as well as better wear resistance than the monocrystalline diamond tool.

Abstract: The main body of grinding knowledge comes from the experiments done by independent investigators. If such experimental results are not made both human- and machine-comprehensible from the very beginning, then it would be difficult to reuse the results using a computerized network or any other means. In this respect, intelligent systems are needed to create human- and machine-comprehensible models of important results like 3D surface finish, cutting force, tool wear, etc. From this perspective, this paper describes a method for modeling and simulation of 3D surface finish of grinding. A human-friendly simulation tool is developed to implement the method. The simulation result is compared with the real 3D surface finish and a close correlation is found. The presented model can be integrated with the collaborative machining networks for better utilization of grinding resources using computers (e.g., condition monitoring, process planning, automation) and even using humans (e.g., effective exchange of information among peers in the research community and in the industry).

Abstract: Two grinding methods, parallel grinding and cross grinding, were applied to the horizontal-axis-type rotary surface grinding of silicon and tungsten carbide. It was found that the cross grinding method results in better ground surface roughness than parallel grinding for the silicon wafer and that an isotropic ground surface topography is achieved for both silicon and tungsten carbide by cross grinding.

Abstract: Single-point fly cutting and nanoindentation test of quartz glass were performed using three different cutting tools, namely, a V-shaped cutting tool, a Vickers indenter and a spherical indenter, to investigate the elastic and plastic behaviors of quartz glass in ductile-regime machining. It was found that these behaviors depend on tool shape and that the V-shaped cutting tool is most effective for removing quartz glass material followed by the Vickers indenter and spherical indenter.

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 effect of cutting-edge truncation on the grinding mechanism of quartz glass as a hard and brittle material was investigated. From computer-aided grinding simulations and experiments on surface plunge grinding it was found that cutting-edge truncation decreases the ground-surface roughness and the maximum grain depth of cut; however, the maximum grain depth of cut approaches a constant value depending on the grinding wheel specifications. The alternative means of making the maximum grain depth of cut much smaller than this constant value is to increase the speed ratio. Cutting-edge truncation should be terminated at the optimum truncation depth to avoid the high grinding forces resulting from the flattening of cutting edges.

Abstract: The elastic and/or plastic behaviors of glass quartz, the most popular optical material and a hard and brittle material, were studied experimentally from two points of view; static mode and dynamic mode. The static behaviors were investigated by a nanoindentation test and the dynamic behaviors were investigated by a single-point fly cutting (SPFC) test. In the experiments, copper was selected as a material representing soft and ductile materials. From the experiments it was found that the plastic deformation ratio of glass quartz is smaller than that of copper depending on the SPFC conditions, and the area coefficient of the pile-up has the same tendency for both glass quartz and copper.