The final objective of this investigation is an invention of theory and technics for multiple precision cylindrical machining with combining ultrasonic vibration cutting on thrust force direction, and superposition superfinishing process. This finishing process is a high efficient mirror machining providing (20-50Hz) low frequent vibration and ultrasonic vibration above 20 kHz to fine abrasive stone. In this report, ultrasonic vibration cutting mechanism on thrust force direction is analyzed and it is shown that high precision machining can be achieved by using the effect of insensitive vibration cutting mechanism. And cutting phenomenon are observed by some experiments. In the results, it is confirmed that chips on low feed rate and high cutting speed conditions have been cut to pieces as same as analyzing, and that work displacement on vibration turning can be reduced according to growing up tool amplitude. This report indicates that ultrasonic vibration cutting on thrust force direction can be possibly used for multiple precision cylindrical machining.
We have developed an automatic measurement system for the efficient evaluation of the switching characteristics of optical MEMS switch modules. In an experimental evaluation of a prototype optical switch module, the insertion loss and the switching time of all optical paths can be measured in the time 1/10 or less compared with the conventional measurement. Moreover, we demonstrated that dynamic optical characteristics, such as electrical and mechanical interferences, can be evaluated automatically. We also confirmed that a practical 3-D MEMS optical switch module can be constructed.
C60 fullerene is used as a carbon source for amorphous carbon film deposition in an electron beam excited plasma. C60 powders are sublimated by heating up to 850°C in a highly vacuumed process chamber. The sublimated C60 is injected to the electron beam excited argon plasma and dissociated to be active species that diffuse toward the substrates. Different negative bias voltages have been applied to the substrate holder to examine the effect of the bias voltage to the properties of the films. Consequently, the carbon species condense as a thin film onto the negatively biased substrates that are immersed in the plasma. Deposition rates of approximately 1.0 μm/h and the average surface roughness of 0.2 nm are achieved. Decomposition of the C60 fullerene after injecting into the plasma is confirmed by optical emission spectroscopy that shows existence of small carbon species such as C2 in the plasma. X-ray diffraction pattern reveals that the microstructure of the film is amorphous, while fullerene film deposited without the plasma shows crystalline structure. Raman spectroscopic analysis shows that the films are one of the types of diamond-like carbon films. The nano-indentation technique is used for hardness measurement of the films and results in hardness up to about 28 GPa.
In this study, in order to apply electrolytic in-process dressing (ELID) grinding for surface finishing process of the sliding parts of metal on metal (MOM) artificial hip joints, a new grinding system to grind the inside surface of a hemispherical cup was developed. In this system, the workpiece was pressurized against the centre of the ball shaped grinding wheel with an oscillating pressure pin during the processing. The shape and the radius of the ball shaped grinding wheel were adjusted by using different size abrasive grains. Hemispherical cup-shaped samples of Cobalt-Chromium (Co-Cr) alloy were ground by this grinding system and their surface smoothness was improved. In addition, the roundness of the specimens was the same as or superior to that of the commercially available sliding parts. This result suggests that this grinding system is applicable as a surface finishing process of the sliding parts of MOM artificial hip joints.
In a conventional automatic programming system developed for turning with a CNC lathe, NC data such as tool path, feed and rotational speed of spindle are automatically generated, when the desired shape of products, and tool and workpiece materials are specified. However, for turning of a workpiece having large length and small diameter, variation in the finished diameter along the rotational axis yields due to workpiece deflection caused by the cutting force. In the case of a shaft that requires machining using multiple tool paths, the magnitude of machining error also varies in accordance with the sequence of the turning process. To reduce the machining error in the diameter, elastic deformation of the workpiece due to cutting force, whose components are obtained through a cutting model and energy method proposed by Usui et al., is considered in the generating process of the tool path. In the analysis for chuck-center work, a finite element model of a rolling center, in which experimental results of bending test are applied, is used. From the comparison of the machining error obtained with turning test for compensated and uncompensated tool paths, it is confirmed that the proposed method is effective in reduction of machining error.
Recently, Geographic Information System (GIS) was widely used for various purpose such as Cityscape Simulation. However, it is required to develop high-speed and large-scale visualization methods to make them work efficiently in practical use. In this paper, we concentrate on the high-speed visualization for large-scale forest landscapes, since it has never been dealt with. The proposed method has the following three characteristic features : (1) It procedurally generates a forest from data sets of the national vegetation survey of Japan. (2) It generates a vegetation boundary which represents a natural arrangement of trees in the forest by using a fractal noise function. (3) To realize high-speed visualization, we propose a generating method of trees which is suitable for parallel processing on GPUs. Several experiments show that the series of techniques can realize the high-speed visualization for large-scale forest landscapes generated from the national vegetation survey data.
Geometric error, such as a pivot offset of the rotational axis, squareness between axes and so forth, is one of fundamental factors that decrease the machining accuracy for five-axis controlled machine tools. And it is important to identify the geometric errors in order to improve the machining accuracy, so that many methods to identify or diagnose the geometric errors of the rotational axes have been suggested. Meanwhile, the most general method for the accuracy test of five-axis controlled machine tool is the cone frustum machining test, which is prescribed in NAS979. In our previous work, we showed that the geometric errors in five-axis controlled machine tools with a tilting rotary table influence the accuracy of machined cone frustum, and it depends on the location, apex angle, tilt angle or diameter of the cone frustum. It indicates that the geometric errors might be identified with the profiles of cone frustum. In this paper, we suggest a method to identify the geometric errors of linear and rotational axes in five-axis controlled machine tools with a tilting rotary table, which uses the multiple trajectories of the conic motion measured by double ball bar device. Moreover we develop the compensation system of the geometric errors. We also show the result of the compensation of the identified geometric errors by the suggested method.