The need for higher accuracy on machined components is always a matter of concern. Accuracy of machined component is determined by the relative motion between the cutting tool and the workpiece. One of the important factors which affects the accuracy of this relative motion is the geometric error of machine tools. Therefore, it is necessary for relating the geometric errors of each structural element to the resultant cutting point error. In this study, for the expression of the relative motion of machine tool elements, a mathematical model utilizing homogeneous transformation matrix multiplications is developed assuming the rigid body kinematics. By applying proposed mathematical model, each geometric error which affects the resultant error can be identified separately. The influence of characteristic configurations of machine tools on the machining error is also investigated.
The purpose of this study is to clarify the machinability of α+β type Ti-6Al-6V-2Sn titanium alloy from the viewpoints of tool wear, cutting temperature and cutting mechanism, which leads to appropriate guidance to manufacturing engineers in the selection of cutting conditions. This paper describes tool life tests performed under a wide range of cutting conditions, and the analysis of cutting economics based on Taylor's tool-life equation. Rough turning of the titanium alloy with straight tungsten carbide tools shows that the combination of lower cutting speed and higher feed rate yields better cutting efficiency and lower cutting cost as well. The machining test in a production environment has confirmed the laboratory result : a 15% reduction in cutting time has been achieved.
This paper investigates the machinability of Ti-6Al-6V-2Sn titanium alloy from the viewpoints of cutting temperature and tool wear. Finite element temperature analysis shows that tool tip temperature decreases with increasing heat conductivity of a cutting tool. Either a diamond or a special tool which enhances heat conduction near the tool tip is recommended for finish turning of the titanium alloy since reduced tool face temperature is favorite for the prolongation of tool life. Using a diamond tool at a cutting speed of more than 105 m/min, not only the cutting efficiency is improved but also the cuttting costs are lessened in comparison with using a straight tungsten carbide tool. A heat pipe-embedded cutting tool is also shown to be effective for the reduction of tool wear.
Using the finite element modelling proposed in the previous paper, orthogonal machining of titanium alloy Ti-6Al-4V is simulated. Chip formation and cutting forces calculated are in good agreement with experimental results. Chip temperature just ahead of tool rake face is higher than tool temperature because of low density, low thermal conductivity and high flow stress of titanium alloy. Almost all frictional energy dissipated on the rake face, 28 percentage of total cutting energy in this simulation, therefore, must flows into the tool. Such high energy share to tool is one of reason for the difficulties in machining this alloy. Normal and frictional stresses on the rake face calculated for titanium alloy are as high as those measured for nickel base superalloy Inconel 750, and about two and a half times as high as those measured for mild steel S45C. Variation of strain rate, stress, temperature, and strain-hardening and strain-softening regions during a chip segmentation of the serrated chip formation are obtained. It is concluded that low fracture strain of the alloy and formation of ductile crack, but not the thermally activated strain-softening, are the trigger for onset of the serrated chip formation, while the softening, which takes place between the tip of fully developed crack and cutting edge, gives high deformability to the chip to be semi-discontinuous.
A new internal finishing process is investigated of a non-ferromagnetic tubing applying a rotating magnetic field generated by electromagnetic coils. To finish the inner surfaces of long or vent clean tubings, a new type finishing equipment is made for practical use. This equipment has conically shaped magnetic coils and magnetic cores consisted of laminated thin electric pure iron plates, so that this equipment is able to be applied to the tubings with the wide range outer diameter from 25 to 150 mm and the temperature rise generated by iron loss of the cores were prevented in lower level. Using this equipment, the finishing experiments were carried out to examine the influences of various factors, especially, finishing tool size, tool weight, tool contact curvature and magnetic field strength, on the maximum adulating revolution of the finishing tool. As the result, the suitable finishing conditions were made clear. Then, from the experiment applying this new process to the internal finishing of a stainless steel elbow tubing which could not be rotated, it was clarified that the surface roughness of 15 μmRmax before finishing was improved to 0.4μmRmax after finishing.
The problem of deciding whether two objects are similar or not is very important in the classification of shapes of objects for robot vision and in the creation of knowledge based systems. This paper describes a method for determining the similarities of two convex polyhedra with unequal number of vertices. The method presented for deciding the similarities of objects with equal number of vertices is extended with the following concepts : (1) In order to calculate the degree of similarity, a method for equalizing the number of vertices between two objects is introduced. (2) The additional factor affecting the similarity, which represents the difference in the number of vertices between two objects, is considered. The results of similarity tests on some kinds of objects show that the method is good for deciding similarities.
A monolithic translation mechanism driven by two pairs of piezoelectric stacks is described which was devised primarily for the mechanical scanner of STM (scanning tunneling microscope). The layout of the mechanism is symmetrical with respect to the center lines of the base plate. Each pair of piezoelectric stacks is cemented at the outer ends between two movable elements of the flexure-hinged linkage which supports a moving platform, and is also cemented at the center on both sides of aluminium alloy square blocks provided on both ends of the base plate. An X-Y translation stage is readily formed by stacking one translation stage on another. It is possible to improve the accuracy of motion of the moving platform by properly adjusting the applied voltage to each piezoelectric stack. Relationship is examined experimentally between the applied voltage and the accuracy of motion in order to attain a high precision translation mechanism. It is demonstrated that the yaw of the moving platform produced by a 46 μm output displacement of the moving platform is reduced from 0.3 arcsec to less than 0.1 arcsec by adjusting the applied voltage to one of four piezoelectric stacks.
The present paper deals with development of an all-in-one PCPS (Percutaneous Cardio Pulmonary Support) system. The system consists of a pump-oxygenator unit and pump controller. The pump-oxygenator unit contains centrifugal pump and extracapillary flow type membrane oxygenator (0.8 m2) in one compact body. Dimensions of the pump-oxygenator unit are as follows : length : 250 mm; diameter : 90 mm; weight : 1 kg. The unit has priming volume of 250 ml. The in-vitro tests (gas exchange, fluid dynamic performance, hemolysis) and an ex-vivo test was conducted. The results are as follows : 1. Fluid dynamic : The system products 1.6-3.8 l/min of flow against 100 mmHg of outlet pressure at a rotation speed of 2 500 to 3 500 rpm. 2. Hemolysis : The increase rate of plasma free hemoglobin was 22 mg·dl-1/h with the PCPS system. 3. Gas exchange : O2 transfer rate of the system was 180 ml/min and CO2 transfer rate was 120 ml/min (V/Q=1) at a blood flow rate 3l/min. 4. Ex-vivo test : The device was operable. In conclusion, the system is considered applicable to cardio pulmonary support.
This paper describes a system which automatically inspects defects in printed circuit patterns. The system is aimed to achieve the maximum defect detection capability, and has the function of automated recognition of fatality of detected defects. The system detects defects by comparing detected patterns with the patterns which are electrically-generated from CAD-data of the printed circuit patterns. Methods to accomplish the targets mentioned above are described : fluorescence detection method for exact pattern acquisition, modulation compensation method of detected signals, precise registration method of the two patterns, defects' fatality recognition method, etc.
The purpose of the study is to establish the six-degrees of freedom (dof) fine motion mechanism which has the following characteristics : (1) each of the six one-dof motions has the same control characteristics as the theist (2) each one-dof motion does not interfere with the others. In the previous study, the mechanism was theoretically designed so that the open-loop characteristics of the six one-dof motions were the same, and so that there were no static and dynamic interferences between the motions. Then an experimental mechanism was made and the six one-dof motions were controlled. In the present study, it is shown that because the six one-dof motions have the same characteristics, the mechanism can make special dynamic motions which other fine motion mechanism cannot make easily. When an extra mass is loaded on the object, dynamic characteristics of the mechanism change from designed ones and the dynamic interference between the one-dof motions occurs. A method to transform the dynamic characteristics into the designed ones and to eliminate the interference is discussed.
This paper describes design, fabrication and performance of the miniature walker developed for a new precision production system. This machine consists of piezo-actuators and electromagnetic legs which are synchronized as to move like an inchworm and those elements are jointed mechanically for the machine to walk on any curved surface including a wall and a ceiling. The magnetic forces of this small machine can be remote controlled critically for preventing from slipping and falling down although conventional inchworm mechanisms need some guide rails or are restricted on a horizontal plane. This arrangement also allows the lack of mechanical elements which may provide a very high positioning resolution with a wider working area. In the experiments, our miniature machines which are the size of golf ball are fabricated and they can move on any inclined surface with continuous sub-micron steps. This results means the mini-walkers have the feasibility for applying to a new precision production system where they can cooperate with conventional machines.
High-speed tape transport mechanisms directly driven by take-up and supply reels are adopted as the large-scale external storage systems or the high-speed search systems of the video cassette recorders and so on. In this paper, the kinetic model of the mechanism is introduced. The relations between the dynamic characteristics and the mechanical parameters are simulated numerically and proved experimentally. In order to improve the frequency characteristics of the servo system, original servo systems are employed newly and the high performance is obtained.
A new method for measuring the three-dimensional coordinate of a microscopic scanning stage is proposed. Four laser interferometers linked with optical fibers are used to determine the position of the corner point of a corner mirror attached to the stage. The three-dimensional coordinate of the corner point is calculated by using only the length information given by the four laser interferometers. The method is traceable from the practical definition of length, and facilitates the optical alignment necessary to the interferometers. A commercial three-dimensional stage is calibrated by the proposed method with the coordinate accuracy of 20-30 nm.