Key Engineering Materials Vols. 389-390

Abstract: This paper presents a fractal analysis of the self-sharpening phenomenon of the grain cutting edges in cBN grinding. To clarify the self-sharpening mechanism due to the micro fracture of the cutting edges, the changes in three-dimensional profile of the cutting edges in the grinding process have been measured using a scanning electron microscope with four electron probes and evaluated on the basis of the fractal analysis. The fractal dimension for surface profile of the cutting edge formed by the micro fracture is higher than that of the cutting edge formed by the ductile attritious wear. Therefore, the complicated changes in shape of the cutting edge due to the self-sharpening can be evaluated quantitatively using the fractal dimension.

Abstract: In contact areas between grinding wheels and workpieces, elastic deformations of grinding wheel take place due to the act of grinding forces. Since grinding wheels consist of abrasive grains and bonds, it may be regarded that the elastic deformations of grinding wheels in contact areas depend on movements of each abrasive grain. However, plural grains are connected each other complicatedly, and then it is difficult to observe each grain behavior. This study aims to directly observe the behaviors of grains in contact areas with workpieces. A small loading apparatus for grinding wheel is newly developed. Inserting a loaded wheel with this apparatus into SEM, grains behaviors in contact area are directly observed. Furthermore, grains behaviors under loaded condition are analyzed with a wheel model developed previously and observed results are compared with analyzed results.

Abstract: Recently, a new drilling technology has been attracting attention using a super-high-speed spindle and micro diameter drills (less than 0.2 mm). In these drilling conditions, B-RING damage extends more than internal damage around the drilled holes. Therefore, we investigated the best drilling conditions for control of the B-RING, considering productivity. The following conclusions were obtained. (1) The temperature of the drilling tool is raised by decreasing the heat capacity of the drill. B-RING damage around the drilled hole is especially generated under drilling conditions using the super-high-speed spindle and micro diameter drill. (2) B-RING is mainly caused by the heat being conducted to the hole wall of the PWB. (3) Raising the R point height is an effective method for preventing B-RING damage. (4) We confirm obtaining the best drilling condition by considering B-RING and productivity.

Abstract: The purpose of this study is to fabricate a wheel using fullerenes with nano-scaled particles, and to investigate the polishing performance of fullerene wheel. A super smooth surface was formed on a silicon wafer by polishing the wafer with metal-bonded diamond wheels using a diamond abrasive grit of 0-0.125 μm and fullerenes with a diameter of 0.7 nm. We used two kinds of metal-bonded diamond wheels for pre-polishing and a metal-bonded fullerene wheel for the finishing process. Though the surface roughness after polishing with the fullerene wheel was almost equal to that obtained by polishing with the metal-bonded diamond wheel using diamond abrasive grit of 0-0.125 μm, the chemical-mechanical polishing process was clarified by AFM (atomic force microscope) observation when we used a metal-bonded fullerene wheel with 5wt% KOH (potassium hydroxide) solution. The greater number of smoothed portions on the surface of the silicon wafer indicated that the fullerenes provided the same polishing ability as that of the abrasive grit.

Abstract: Ultrahigh speed grinding is a kind of high efficient metal cutting method. In order to improve ability of ultrahigh greed grinding wheel spindle to resist vibration and grinding quality, an ultrahigh speed grinding spindle system with a squeeze film damper (SFD) was designed based on the theory of squeeze film damping technology. Pressure distribution and squeeze film stiffness characteristic of SFD was study by the method of simulation. Based on theory study an ultrahigh speed spindle system with a SFD was designed and experiments were done. The study results show that application of SFD technology can effectively restrain vibration which is caused by the imbalance quality when the grinding wheel spindle turning at ultrahigh speed. And the speed of the grinding spindle is higher and the effect of attenuation of SFD to grinding spindle is better. Research works provides a new technology for the design of the ultrahigh speed grinding spindle system.

Abstract: Single crystalline diamond grains covered by nested carbon nanotubes (CNTs) were constructed using self-assembly techniques. The acid-treated CNTs (MWCNTs-COOH) are first adsorbed onto amine-terminated diamond grains, which were chemically functionalized by silane coupling treatments, in N, N-dimethylformamide solution. Then, the drying and readsorption cycle deposited CNT coatings on the diamond grains due to CNT-CNT interactions caused by van der Waals forces. When the diamond grains were bonded to steel substrates by electroplating using nickel sulfamate plating bath, the bonding strength of the CNT-coated diamond grains to the Ni matrix was almost twice as large as that of the normal diamond grains. Hence, the CNT-coated diamond grains are very useful for improving the tool life of electroplated diamond tools.

Abstract: In order to enable the recycling of FRP waste, the pulverization method is proposed based on surface grinding process. In the experiments, the pulverization characteristics are examined, and then, the change in the property of the FRP material pulverized to particles is confirmed. From the examination, the following were clarified: The FRP material can be pulverized with surface grinding process, and the sizes of the generated particles are almost 10μm or less. The size distribution of the generated particles hardly changes regardless of the change in grinding condition, such as depth of cut or feed rate. However, the increase in depth of cut or feed rate makes the particles easily cohere together. To improve the pulverization efficiency, the supply of the semi-cold-air is effective because this markedly prevents the particle cohesion. The pulverization improves the water suspension ability of FRP in water, and this gives FRP waste the possibility of recycling.

Abstract: A robust measurement method for vertex position of a small polyhedron using 3D image procession is proposed. Shape from focus method is applied for getting 3D positions on surfaces of the polyhedron. Averaging of in-focus function is usually applied for reducing noises, but it lacks sharp edge information of the target. The position of the vertex is indirectory calculated from the 3D data using geometrical model of the polyhedron. In this paper, relations between measurement noise and appropriate number of data for averaging of focal measurement, and area of data for fitting of the Gaussian function were investigated. Then, error propagation analysis is applied to the equations of the indirect measurement of the vertex position. By using the geometrical characteristics of the polyhedron, measurement of the vertex position became robust against the measurement errors. Effectiveness of the proposed method was confirmed by numerical simulation and experimental result for measurement of a vertex of a small polyhedron.

Abstract: This paper looks at the multiple characteristics and investigations of two grinding anomalies: grinding burn and grinding chatter. A genetic programming (GP) of multiple classifications was investigated for different machining strategies and associated anomaly phenomena. Such a GP paradigm could evolve rules to provide the correlation between monitored signals and grinding phenomena. The investigation also looks at both Short-Time Fourier Transforms (STFT) and Wavelet Packet Transforms (WPT) to convert the raw acoustic emission (AE) signal into a time based frequency signal, segmented into different frequency bands. A set of encouraging results is presented.

Abstract: The use of aspherical optical parts has become common as optical instruments are becoming smaller with and are achieving higher resolution. Nano-order roughness and high-precision shapes are simultaneously required for the surface of aspherical optical parts. At present, form accuracy of the aspherical lens becomes less than 50 nm, and the maximum height roughness becomes less than 20 nm. These values of form accuracy and maximum height roughness satisfy the requirement for most precision optical parts. However, nano-topography, which causes grinding marks and deteriorates accuracy of optical parts, is generated on the ground surface. Conventional evaluation criteria such as form accuracy and surface roughness cannot estimate the nano-topography. In the present paper, the cross sectional profile of the axisymmetric ground surface is calculated in order to estimate the distribution of the nano-topography. As a result, the possibility of control of the nano-topography distribution is confirmed. In addition, controlling the amplitude of nano-topography is easier than controlling the distribution of nano-topography.