[in Japanese]

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[in Japanese]

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A laser multi-sensing technique for detection and determination of various kinds of microdefects on diamond turned surfaces of magnetic disk substrates has been designed and implemented on a fully automatic surface inspection system. The technique includes the following three sensing methods : (1) a laser diffraction pattern method using a wedge-ring detector array (WRD), which identifies steep-sloped defects such as pits, scratches, and periodical machine marks ; (2) a laser beam deflection method using a position sensitive detector (PSD), which identifies smooth-sloped defects ; (3) a reflectivity method using a pair of photodiodes corresponding to the detection of the incident and the reflected beam intensities, which identifies reflectivity-changing defects such as stains and erosions. The automatic inspection system consists of laser optics and signal processors for multi-sensing, a disk handling and scanning mechanism, and a host computer. Using a multi-sensing technique, the host computer determines the surface quality and controls the mechanism. Experimental results for a number of disks confirmed that the system can detect and determine defects at a high rate of up to 25 s/ side for 5.25'' disks with a reliability equal to or better than that of specially trained visual inspectors.

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A method to connect a surface patch to adjacent patches at the four boundaries with the condition of positional and gradient continuity has been developed. This method makes it possible to connect surface patches symmetrically, even if the boundaries of the surface patches are symmetrical along the common boundary. A new surface expression which makes it possible to control the inner shape of a patch, keeping positional and gradient continuity of all local surface patches has been developed. Also, a new method which interpolates the inside of a surface patch when the four boundaries of a surface patch are defined has been developed. Both a normal vector and contour line display of a six-sided patch connection, and a highlighted line display of a spherical surface are shown.

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This paper deals with a processing system for extracting undercut in mold designing. The development of such a system involves the solution of two problems. One is how to extract those parts which may form undercuts-the parts that may be called “potential undercuts” -from the shapes of moldings. The other is how to determine on the optimum direction of withdrawal of moldings. In solving the first problem, we worked out a new method for extracting potential undercuts; this method comprises the determination of three-dimensional convex hull and set operations. The approach to the second problem was the use of the simplex method, one of the nonlinear optimization methods, to find the optimum direction of withdrawal of moldings. A case study was then conducted to verify the usefulness of the processing system thus developed.

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In this paper, the behaviour of the bolt head deformation of the hexagon socket head cap screw in connecting is examined in detail by the finite element method, and then the method of the precise and direct axial tension detection which is impossible so far, is proposed using its deformation characteristic. The main results are as follows : (1) The bottom of the hexagon socket makes sinking deformation in nearly parallel. (2) The change in the distance between the fixed position of the sensor in the socket and the bottom of the socket is in good proportion to the bolt axial tension. (3) The detecting method of the axial tension using this relation makes possible to detect directly and precisely the axial tension of the hexagon socket head cap screw. (4) The influences of the angular position of the sensor to the hexagon socket and the fixing position in the socket on the sensor sensitivity are small. (5) The influences of the materials and hole diameter of the washers are small and that of the parallelism of them is great. And in the case of standard washers, the influence of the eccentricity of them is small.

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This paper describes the effect of residual thread torque at the termination of tightening on elasto-plastic deformation of bolts under external load after bolted joints are tightened in plastic region. Firstly, the effect of residual torque is analyzed by use of the flow theory of plasticity, and then the relationship between axial tension and thread torque of the bolt is obtained experimentally. The obtained conclusions are as follows : (1) At the beginning of the external loading, after tightening there is the region regarded as elastic deformation on the relation between axial tension and elongation of the bolt, which is extended with the decrease of residual thread torque. (2) It is recommended to slightly loosen the bolt or the nut after tightening so as to reduce residual thread torque to zero, in order to decrease the additional plastic elongation of the bolt.

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Grinding efficiency, wheel wear and grinding ratio are evaluated in plunge grinding under the concept which abrasive grains cut the workpiece, as well as tips on the ground surface scratch the bond of grinding wheel. Grinding ratio is related with Young's modulus, the elastic failure energy and the visco-elastic properties of bond. The estimated values which may present the grindability of wheel are verified in the grinding tests with poreless vitrified bonded diamond wheel in regard to the contents of frit, kinds of grains, grain sizes and concentrations. High grinding efficiencies, much wear of wheel and low grinding ratios result in low contents of frit, brittle grains and large grain sizes. Large elastic failure energies of bond predict little wear of wheel and high values of grinding ratio which are verified in the tests.

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A characteristic equation of carbide tool wear in interrupted turning operation is derived and verified experimentally to hold well by measuring the distributions of wear, stress and temperature on rake face at the steady state. A computer simulation of crater wear development is then carried out by applying the wear equation, of which the characteristic constants are obtained from a single wear test. The change of cutting stress distributions on rake face at the engagement with the crater wear development is obtained experimentally. The crater wear does not any effect on the variation of cutting forces during the engagement but on the distributions of cutting stress at the instant of impact. A tool-chip contact length is limited within an area between the cutting edge and the front edge of crater at the moment of impact. For the arbitrary wear development, the transient variation of impact stress field within cutting edge during the edge engagement in interrupted turning is obtained though FEM calculation using the stress distribution obtained above. In collation of the most dangerous state of the transient stress with the fracture criterion at each element for the arbitrary wear state, both the variation of fracture probability distribution with number of interruption and the wear development with cutting distance can be also predicted.

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This report deals with the grinding temperature at burning threshold in wet grinding. The workpiece burn in both up-cut and down-cut dry grindings, and in down-cut wet grinding occurs at almost the same maximum grinding zone temperature of about 500°C. However, in up-cut wet grinding, the maximum grinding zone temperature at burning threshold is somewhat higher than that in down-cut grinding because the workpiece surface with high temperature just after up-cut grinding is cooled rapidly in comparison with that in down-cut grinding depending on the location of injecting nozzle. The metal removal rate at burning threshold, (Z_ta) _b, becomes smaller in dry grinding than in wet grinding. The value of (Z_ta) _b in both wet and dry grindings becomes larger with higher table speed. The value of (Z_ta) _b for oil type grinding fluid becomes larger than that for soluble type grinding fluid.

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In this study, a high speed spindle supported by aerostatic bearings has been produced for machining centers or NC milling machines, and a couple of displacement detectors have been built into its unit in order to detect the cutting forces and the tool failure. In the experiments, the static and the dynamic characteristics of the spindle are measured, and also both radial and axial displacements of the spindle are investigated as well as the cutting forces and the electric power in practical use. From the experimental results, it is found that the cutting forces of thin drills and/or thin end mills can be detected by the displacement of the spindle as well as tool failure.

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In this study, alumina ceramics are ground with vitrified diamond wheel and cluster wheel, which is a metal disc mounted with a cluster that is a small piece removed from the diamond wheel. The grindability on surface roughness, grinding force and chipping are experimentally investigated. The results obtained are as follows. Ground surface of alumina ceramics that contain more than 99 % Al₂O₃ are mostly occupied by transgranular or intergranular fractures, but those less than 99 % Al₂O₃ are approximately half by plastic flow. In three dimensional roughness curve, large variation of interval between surface roughness curves means poor grindability. Therefore surface roughness measured along grinding direction is suitable to evaluate grindability of ceramics. When grain size of ceramics becomes large, chipping and surface roughness increase but grinding force decreases.
Other ingredients, impurities, additives and firing condition have effects on surface roughness and grinding force.

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The failure characteristics and the cutting ability of TiC added alumina ceramic tool when face milling SKD 11 were studied. The tool failures when milling SKD 11 with a hardness over HRC 50 were grouped into three types : wear caused gradually by adhesion and peeling off of the work material onto the cutting tool (type 1), large fractures caused rapidly by scooping on the rake face and chipping on the cutting edge (type 2), and large fractures caused suddenly by thermal cracks in the rake face (type 3). Which type of failure occurred to cutting edge was related to the cutting speed, engage angle and disengage angle. The engage and disengage angles also influenced the tool life ; the disengage angle had a greater influence than the engage angle. In the case when the cutter had a bigger diameter than the work width, the more the disengage angle increase, the more the tool life became long. On the other hand, in the case when cutter had a smaller diameter than the work width, as the engage and disengage angles became larger, i. e., the more the cutting width became wider, the more the tool life became long. There is the most appropriate cutting speed which to extends the tool life.

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The development of bond has been based on a practical experience of human expert who subjectively evaluates its performance. In this study, a mathematical model derived from the subjective evaluation process is proposed, and a newly-developed technique for deciding the combining ratio of composition of bond is established. The model determines the over-all evaluation of the performance of pure fired bond, by taking the fuzzy integral of several characteristics of bond with respect to the subjective measure, expressing the degree of importance of each characteristic. The most desirable combining ratio of compositions can be decided by the model, since the characteristics, i. e., the melting temperature, the coefficient of thermal expansion, the bending strength, the percentage of pore and the wettability to the grain are closely related to the combining ratio.

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This investigation examines the fracture initiation from a pre-existing defect and a surface defect by the transverse rupture test for cemented carbides based on fracture mechanics. The stress intensity factor, which was calculated by the pre-existing defect size and the nominal stress acting on the defect, was smaller than the fracture toughness of the materials. Acoustic emission signals were detected before the ultimated fracture of the specimen occurred. The stress intensity factor determined from the stress in AE signal detected and the defect size corresponded to the fracture toughness of grain boundary of carbide particles. Then, it was suggested that a microcrack grew locally near the defect. Taking the microcrack into consideration, it was found that the stress intensity factor coincided with the fracture toughness. For the fracture initiated from the surface defect when the machining damage may be small, the defect size based on fracture mechanics was equal to microcrack length. Therefore this microcrack must be considered in the estimation of machining damage of sintered brittle materials.

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In this paper we discuss the cause of an oversized effective diameter by tapping for a large size threads and investigate the prevention method for it. We carried out the simulation using the imitated cutting edges and turning test and the tapping using M 42 × 4.5 tap. The results are as follows. (1) Axial oversize thread can be caused on a following flank when the direction of the over thrust is same as the direction of tapping. When it is reversed, the over thrust can be caused on a leading flank. (2) Where axial force is constant, the effective diameter at the inlet of the thread is larger than at the bottom (Bell-Mouth phenomina) because the thrust force acting on a unit length of cutting edge can reduce exponentially according to the increase of cutting edge. (3) In order to prevent producing oversize threads, it is necessary to develop a new tapping attachment controlling the axial thrust on the initial tapping and the reverse rotating.

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In the finish roll forming, it inevitably yields both the concaving of tooth profile and the plastic deflection of addendum of teeth. In this paper, a new method for the rolling is proposed and examined to avoid both errors. In the method, screws or cams with sufficiently high rigidity are used for a working apparatus. At first the some amount of displacement between workpiece and tool is forced corresponding to the stock allowance. Then, the displacement keeps constant during rolling. Experiments show that the concaving and the plastic deflection are successfully reduced. As the results both contact stress and difference of angular velocity between tool and workpiece are kept constant in rolling process. The accuracy of tooth profile reaches to JIS 0 Class in the experiments.

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To understand the, vibration characteristics and the machining performance of a phetoiype milling spindle system with electromagnetic bearings, computational structure dynamics analysis and excitation test have been conducted as well as high speed (36000rpm) end milling wrought aluminium alloys. It has been known that the maximu speed of the tested spindle system is limited by a natural frequency of tie spindle identified as about 800Hz, and also the stiffness cf the spindle needs to be increased for higher speed rotation as well as improved machining performance using wider variety of cutting tools. Based on the computational analysis, alternative spindle designs have been proposed.

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In CO₂ laser processing, laser beam is converted to have an adequate energy distribution for a processing purpose. This paper describes in both calculation and experiment what energy distributions have been obtained by kaleidoscopes of cylindrical pipes. Calculated without respect to interference, the energy distribution of a single-mode laser beam approaches that of a higher energy concentration on the center of kaleidoscope outlet as its length increases. The calculation with respect to inter ference indicated that interference fringes appear on energy distribution. Cylindrical pipes of which inner diameter is less than hundred times as large as laser wavelength can concentrate the energy on the center of the outlet by utilizing the influence of interference that depend on kaleidoscope length. The same kind of calculation was done for multi-mode laser beam. Calculated without respect to interference, the energy distribution which concentrates the energy on the center of kaleidoscope outlet changes periodically as kaleidoscope length increases. The calculation with respect to interference had the same tendency as that for the single-mode. In experiment, acrylic burn patterns have been made by cylindrical kaleidoscopes of which inner diameters are both more and less hundred times than the laser wavelength in order to verify the conversion of single-mode beam. The experimental result has been in accordance with the calculation with regard to interference.

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This research aims at developing a method of numerical calculations and clarifying the characteristics of a roundness error reducing process in rubber contact wheel type belt grinding. Cylindrical plunge belt grinding was carried out on the eccentric workpieces in place of workpieces having a roundness error. Judging from the results obtained by comparing the eccentric workpieces with the normal round workpieces, there was little difference in the forming process, regardless of the infeed conditions. Therefore, a model of the deflectionreducing process of the eccentric workpiece was estimated. Using this model, a deflectionreducing process by numerical calculations was proposed and it was confirmed that its results were in close agreement with the experimental results. So, the effects of the grinding conditions on the deflection-reducing process were calculated. As a result, the characteristics and problems were clearly recognized for the grinding of eccentric workpieces.

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