Papers by Author: Haruhisa Sakamoto

Abstract: This study concerns the rational determination of machining conditions for micro endmills that are less than 1.0mm in diameter. The characteristics of machined surface roughness are measured according to machining conditions, especially the feed per tooth Sz. The machined surfaces conditions are also observed with SEM. From the experiments, the following are made clear: (1) The feed per tooth Sz at the critical value Szc makes machined surface roughness the finest. (2) The conditions of Sz larger than Szc make cutting marks regular, that is, stable cutting can be done under those conditions, and then, the roughness improves according to decreasing Sz. (3) The conditions of Sz smaller than Szc cause irregular machined surfaces including pileups and diggings, that is, cutting becomes unstable conditions. The excessively thin chip-thickness prevents from stably engaging edge on workpiece surface. (4) Although the values of Szc are independent from the type of machine tools and cutting speeds, the values decrease according to decrease in tool diameter. (5) The value of Szc increases when tool has worn over its limit. Therefore, in order to determine machining conditions rationally, the changing behavior of Szc should be understood according to tool wear.

Abstract: In previous study, the quantitative measurement method of contact stiffness of the joint considering real contact area is developed by experimental approach. However, the measurement of contact stiffness needs special device and skillful measuring technique. Therefore, in this paper, simplified calculation method with material properties and profile data of surface roughness obtained by profilometer is considered. As a result, real contact area, contact stiffness and contact spring stiffness calculated from specific wavelength of rough surface are near agreement with experimental value. Hence, it is revealed that there is dominant configuration in surface roughness.

Abstract: In this study, the novel finishing method of the Micro Lens Array mold is proposed. This method combines the cutting by a ball-endmill and the finishing by sphere indentation. In the previous step, U-shape grooves intersected at right angle are machined by a ball-endmill. In the following step, the ball tool indents at the intersection between U-shape grooves, consequently, the aiming lens form and the aiming surface roughness are obtained. From the results of the manufacturing experiments of the MLA mold by this method, the following are made clear : The proposed method is effective to suppress the deformation of neighboring lens forms caused by following indentation. The improvement effect of sphere indentation on the finished surface roughness is remarkable in the early stage of indentation. The transcribing deviations are 12μm or less in comparison between the radius of lens form and the ideal value regardless of radii in grooves previously cut. In case of the indentation of neighboring four (2 × 2) lenses, the deviation reduces down to 3μm.

Abstract: In this study, the effects of clamping toolholders on the dynamic characteristics of spindle systems are evaluated experimentally. In the experiments, the transfer functions are obtained by the impulse response method, and then, the dynamic characteristic parameters are identified based on the vibration model of single-degree of freedom. Two types of machining center spindles and four types of toolholders are evaluated. From the experimental results, the following are revealed: (1) the clamping toolholder enhances the vibration amplitude markedly compared with that of the spindle not clamping toolholder. (2) The different chucking mechanisms clearly change the dynamic stiffness of the spindle systems. (3) The order of magnitude of the dynamic stiffness of the spindle systems agrees well with that of the isolated toolholders. It is confirmed experimentally that clamping of the appropriate toolholder improves the dynamics stiffness of the spindle systems for machining centers.

Abstract: In this study, we examined influencing factors on the identification accuracy and improving method of the identification accuracy. As a result, the influence of the condition of the dynamic characteristic values is large and these values should correspond to the tangential and vertical directions. The influence of treating dynamic characteristic parameters of the same plural joints is also large, and then the parameters of the same plural joints should have the same value. In addition, the tangential dynamic characteristics should be identified from the vibration mode which has large tangential relative displacement between the joint interfaces. Similarly, the vertical one should be identified from the vibration mode which has large vertical relative displacement between the joint interfaces. Finally, the identification accuracy can be improved greatly by considering these influences.

Abstract: In this study, the determination method of the number of the effective cutting-edges had been proposed based on the measurements of working surface topography and the grinding force. Furthermore, its validity is made clear based on the topographical analysis of the ground surface roughness of pure copper, which is excellent in transcribing the working surface. From the results, the following are found out: The ground surface topography contains the periodical component, which is originated in the grinding and dressing conditions, on the fractal noise component. The cutting traces by each cutting-edge can be countable from the ground surface profile, and then, the number of the effective cutting-edges is identified at one line within the working surface. On the other hand, the number of the effective cutting-edges also can be identified based on the working surface, but, this method requires the determination of the typical grain shape. From the experiment, it is confirmed that the grain shape should be almost spherical for making the numbers of the effective cutting-edge identified from the working and ground surfaces equal.

Abstract: The grinding should be improved to be the skill-free process executed based on the quantified criteria. In this study, the evaluation methods are applied to evaluate the dressing process to clarify how the dressing changes the cutting-edge distribution. From the results, the following facts have been clarified: There is the critical value of the depth of cut for suppressing the release of grain. The spark-out in dressing releases grains damaged by collision with dresser, and then, it also increases the cutting-edge density.

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: 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 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.