[in Japanese]

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[in Japanese]

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[in Japanese]

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The number of people who are over 65 years old is rapidly increasing. It is predicted that the rate to total population exceeds 25 % in around 2015. Such increase of population in advanced age will cause increase of total demand of prosthetic teeth. Therefore sufficient supply of prosthetic teeth with reliable quality will be important social requirement. To meet the requirement, the system which produced prosthetic teeth in industrial way by applying CAD/CAM technology has been developed. As the first stage, multilayer boundary representation cell constructive model (MCCM) which is able to represent configuration of prosthetic teeth, is reported. It is also possible for representation of objects having multilayer constructions as natural teeth and other living organs. Furthermore this model can represent flexible structure by setting appropriate attributes.

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In order to check the kinematic performance of an assembly, a kinematic model of assembly using contact constraint representation in configuration space was proposed in previous paper. In this model, the region of motion without collision is derived in configuration space from the imposed contact constraint. However, it is difficult to represent the motion since time is not taken into consideration. The objective of the research described in this paper is to introduce time into this kinematic model. This is accomplished as follows : first, by introducing configuration-time space, an expansion of the contact constraint representation is proposed. Second, based on this representation, a method for deriving the region for the position and orientation of the components in an assembly is proposed.

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“Virtual Manufacturing” is one of the most attractive techniques in the field of manufacturing. In order to make a Virtual Shop Floor (VSF) as a first step to build Virtual Manufacturing Systems, Open System Architecture for Virtual Shop floor (OSAViS) is presented. OSAViS is an architecture to make the VSF as a set of various modules and execute a distributed and parallel simulation of shop floors. In this paper, a data management method, a synchronization process, and a communication mechanism in OSAViS are described. These subjects are important to simulate shop floors on a distributed and parallel environment. Based on OSAViS, a pilot system named Open-VirtualWorks is being developed so as to evaluate the validity of OSAViS. The current system can simulate behaviors of automated guided vehicles on a shop floor. By modeling and simulating with this system, a validation of the data management method, synchronization, and the communication mechanism is done, and the effectiveness of OSAViS is shown.

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Realtime tool path generation is effective for machining surfaces precisely of a die and enables to respond to changes of conditions like the diameter of a cutting tool. The software for the realtime tool path generation is required to be able to generate collision-free tool paths in high rate and to be reliable. In this paper, a new method is proposed for tool path generation based on a surface model. The method has a feature that collisions between a tool and surfaces are detected and avoided quickly and stably in a process based on surface subdivision. Simulated results show that the proposed method enables to generate tool paths for not only ball end type but also other types of tool, and generate tool paths immediately even if conditions like a using tool are changed, and generate tool paths in high rate enough to apply the method to the realtime tool path generation.

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It is important to investigate the influence of microstructure on the behavior of welded joint for the design and life assessment of the welding structure. This paper shows the possibility of applying holographic interferometry to the analysis of displacement behavior of welded joints. The specimens were prepared from the joints of pressure vessel made by multilayer welding. The deformation of the cylindrical surface with base metal, heat affected zone (HAZ) and weld metal structure under the axial load are measured continuously by real-time holographic interferometry and the effect of microstructure is discussed. The experimental results indicate that the location of HAZ for loading direction has predominant effects on the deformation of welded joints.

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Selection of the control method is the first step of controller design and an important aspect of the system design. Leadscrews are typical precision straight motion mechanisms which have a long working range. Although many kinds of control methods have tried to be used for the mechanisms, the most suitable control method for them has not been yet clarified. The purpose of this research is to solve the problem by simulation and experiment. For this purpose, this paper discusses the performances of the positioning systems with two kinds_of intelligent control methods such as the neural control and the fuzzy control ones. The neural controller consists of a three layer neural network, a back-propagation unit and a nonlinear reference model. The fuzzy controller comprises two sub-controllers. Both controllers are designed by using the characteristic of the mechanism which is expressed on phase plane. Their performances such as positioning accuracy, positioning time and repeatability, as well as effect of Coulomb friction force, step height, the table mass and constant load changes on the performances are evaluated by simulation and experiment. These results prove that both controllers have good positioning performances, especially, the system with the fuzzy control has the best one.

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This paper describes two mechanisms in ultrasonic-vibration assisted microdrilling. In the first experiment, the mechanism of the beginning of penetration was examined using a quick-stop device. In the second experiment, the chip formation mechanism in deep hole drilling (L/D=7) was examined. The drills with a diameter of 1 mm are clamped in a spindle ultrasonically vibrated with 40 kHz in axial direction. When applying ultrasonic vibration the wandering of a drill at the hole entrance is inhibited because of the hammering motion of the chisel edge and reduction of cumulative displacement of drill due to intermittent cutting. In addition to these effects, reduction of friction and increase in rake angle of the chisel edge improve the performance of drilling at the hole entrance. Ultrasonic vibration makes chip flow angle larger and chip side curl curvature smaller. One reason for this phenomenon may be that chip flow velocities at the inner and outer corner do not differ much, because the velocity component of ultrasonic vibration occupies the major part in the cutting velocity. Another reason may be the improved cutting condition at the chisel edge.

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Brittle materials like semiconductor wafers and ceramic substrates are usually cut by diamond tools, where the generation of microcracks cannot be avoided. Recently, thermal stress cleaving of a thin strip using a point heat source is studied to cut brittle materials without leaving any microcracks on the cleaved surfaces. However, this method often causes thermal damages to the workpieces because of the very high temperature reached around the heating point. It is desirable to cut the electronic substrates, on which precise circuits were already formed, with minimizing the temperature rise. In the present paper, based on the plane thermoelasticity, the time dependent thermal stress intensity factor of a line crack has been obtained for two heating ways : by two point heat sources and a circular zone heat source located symmetrically with respect to the crack line. It was found that a zone heating is better than a point heating in the case of a thin strip cleaving under the restriction of the temperature rise. The most successful cleaving is generally achieved when a radius of a heating region is expanded up to the crack tip. The present calculation was compared with the experimental results and good agreement was found.

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Hard and brittle materials such as silicon, glass and ceramics have two modes of material removal, ductile and brittle. There is a ductile to brittle transition between two modes. When the depth or the force of a cut exceeds some threshold value (i.e., critical depth or force), the material removal mode will change from ductile mode to brittle mode. If the critical depth or force can be obtained by a simple test, it can be expected to apply these values for the practical ductile mode cutting or grinding. In this study, a microindentation tester which can detect crack initiation by acoustic emissions (AE) sensor was developed. As a result, after the AE signals generate during microindentation test of single crystal silicon, the cracks are observed by an atomic force microscope (AFM). Therefore, the microindentation with the cracks length of greater than 1μm is defined as brittle mode and the critical values of ductile to brittle transition is obtained. The critical values in this microindentation tests are from 40mN to 50mN in load and from 0.55μm to 0.65μm in depth. The relationship between plastic deformation volume and plastic deformation energy was also discussed from the load-deformation characteristic curves in the microindentation tests.

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This paper describes a new machine that employs lapping tape to fabricate spherical mirror-finish surfaces on PC (physical contact) connectors to be used in optical fiber communications networks. A convex spherical surface can be obtained by rotating the PC connector while pushing it perpendicularly against a concave surface covered with lapping tape. A palm-size processing machine employing this technology has been built. This processing-machine, successfully produces PC connectors having sufficiently high optical light transmission characteristics.

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Atomic-level material removal process of HOPG (Highly Oriented Pyrolytic Graphite) is analyzed by STM (Scanning unneling Microscope) and MD (Molecular Dynamic) simulation. By using STM tip scanning system, the material removal such as indentation and scratching is carried out in atomic scale. This deformation process is also analyzed by MD computer simulation. The trace on several nanometers generated by STM tip machining is observed, but undeformed region which shows typical atomic arrangement of graphite is recognized near from the deformation region. Good consistency between experiment and calculation can be found.

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Burr formation in milling is a three dimensional deformation. Burr formation is different from deformation in continuous cutting. In burr formation on exit surfaces of workpieces, the continuous cutting before burr formation is considered to be an initial condition of bur formation and plastic deformation of workpiece edge formed by the tool exit is burr. Therefore, the continuous cutting and deformation by tool exit have effect on burr formation. To clarify the effect of these factors on burr formation, burrs created with various axial rake angle of the tools and cutting conditions were observed. To represent the state of the continuous cutting, the chip flow angle calculated with cutting conditions was used. To represent the deformation type at the workpiece edge, exit order of cutting edges calculated with the geometry of the tool and workpiece edges was proposed. These chip flow angle and exit order are used for understanding the burr formation in milling. To vary the chip flow angle and exit order, depth of cut, feed and axial rake angle of tools were varied. As the results, it was verified that deformation formed in continuous cutting and tool exit has effect on burr size in face milling. As the chip flow angle increased, the exit burr thickness decreased and side burr thickness increased. As the axial rake angle decreased, the exit burr thickness increased with effect of the exit order. These chip flow angle and exit order are considered to be important factors on burr formation in milling.

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Micro-tribological studies are made using a scanning probe microscope (SPM) which can measure the lateral force as well as the normal force images. The SPM is placed in an atmosphere control apparatus and the relative humidity around the tip-sample is controlled at 30% or 70%. Measurements are also performed in a high purity water bath. Samples investigated are the cleaved surfaces of mica, HOPG and MoS₂. In order to discuss the micro-tribological effects of adsorbed water molecules and the capillary condensation of water, the lateral force images are examined quantitatively as a function of the normal load on the sample surface. Lateral force images with the lattice periodicity are obtained in the same manner as atomic scale topography images. The dependence of lateral force magnitude on the normal force is found to be affected by the atmosphere around the tip and the sample. From discussion on the viewpoints of Hertz analysis, Elasto-Hydrodynamic Lubrication and capillary condensation of water, the contact mechanism of the tip-sample is revealed.

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A new round-off truing method of a grinding wheel, utilizing an abrasive stick and the circular motion of a CNC grinding machine, is proposed. In this method the stick is set on the table of the grinding machine, and a grinding wheel is moved around the stick using the circular interporation. During the consecutive circular motion and down feed, the wheel and the stick grind each other and their surfaces become round. The truing mechanism is examined by a computer simulation and following results are obtained. The radius of the wheel surface changes with truing pass, and it settles a certain value which can be geometrically estimated. The factors in the settled radius are the width ratio of wheel and stick and the radius of the circular motion. Although the wear ratio of the abrasive stick, α, hardly influences the settled radius, it affects the forming process. When a grinding wheel and an abrasive stick have the same width, α = 0.5 is the most efficient condition for the round-off process. Trued wheel surface has a form error especially on its ends, and the error linearly diminishes with down feed.

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This paper describes a newly developed cutting force and temperature measuring device with high response speed and fine resolution. It can monitor cutting process as well as tool wear during high-speed endmilling of hard steel materials. The device enables precise determination of the transient cutting force and temperature which are generated by each cutting edge of an endmill tool rotated at a speed of 20000 rpm. It is found that the cutting force and cutting edge temperature in high-speed milling are affected markedly by the cutting speed and tool wear. The cutting force and cutting edge temperature proportionally increase with increasing cutting speed.

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A high-resolution scanning phase-measuring acoustic microscope was used to investigate the near-surface residual stress distribution in mono-crystal silicon and pure aluminum. The 4-point bending device was newly developed and used to measure an acoustic.velocity applied stress curve for the materials. The stress dependence of acoustic velocity was presented and compared with a theoretical result. Image of the stress field at the diamond ductile cutting surface of monocrystal silicon was observed. The stress distribution by the acoustic method was much the same as that by the micro-laser Raman method. It was found that the acoustic velocity in pure aluminum at the prastic deformation field was non-linear and satulated.

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The temperature of the flank side of the cutting tool edge that has large affect on machined surface integrity is measured using two-color pyrometer with a fused fiber coupler. The infrared rays radiated from the cutting tool edge are accepted by an optical fiber, and separated to two optical fibers at the fused fiber coupler. Each fiber leads the infrared ray, respectively, to two infrared detectors with different characteristic of spectral sensitivity. Temperature is obtained by calculating the ratio of the output voltage from these two detectors. A CBN tool (CBN content : 60 volume percent, density : 3000 kg/mm²) is used as the cutting tool. Annealed steel (S45C), bearing steel (SUJ2), and quenched steel (S55C) are used as the cutting materials to investigate their affect on the tool edge temperature. The results obtained are as follows : (1) The technique developed is suitable for measuring the temperature of the flank side of the cutting tool edge. (2) The temperature of the cutting tool edge is highly effected by cutting speed. (3) The temperature increases slightly with the increase of depth of cut and feed rate. (4) On the cutting of quenched steel which has the largest hardness among these three materials, the temperature is about 50°C higher than that on the bearing steel cutting, and the temperature of the annealed steel cutting is the lowest.

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The author proposed a new system called the workpiece-referred form accuracy control system (WORFAC), and confirmed an effectiveness of this manufacturing method. It is direct control method of the relative displacement between cutting tool and workpiece used by in-process measurement. Since the displacement sensing is based on the workpiece surface, for the precise cotrolled cutting, the first reference surface with a good quality is essential. To obtain a well defined first referece surface, a controlled cutting with a reference surface (CCRS) is proposed. This method is a way of controlling the depth of micro-cutting by in-process measurement of distance between the tool and the reference surface. The second and following surfaces are made by WORFAC referring to the first and previous reference surfaces. An accurately contolled surface can be made to all over the workpiece.

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