[in Japanese]

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[in Japanese]

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[in Japanese]

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A planar linkage is described which was devised primarily for micropositioning stages. It functions both as a magnifying or reducing mechanism and a guidance system for a rectilinear motion. Two input bars, which are coupled to a driving element such as a piezoelectric stack, two output bars, one of which is mounted on a base plate and the other performs the function of a moving platform, and four connecting bars, eight bars in total are connected together by flexure pivots. A displacement amplification or reduction is effected according as the angle between the input and connecting bars is larger or less than 45°. Design formulae are given for the linearity between the input and output displacements and a decrease in magnification caused by an elongation of the flexure pivot. A differential linkage, which combines a pair of linkages, is presented for improving the linearity. Description of the experiments performed for evaluat-ing the validity of design formulae, is included.

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This paper introduces ultra-precision positioning technique with linear motor. In order to realize a compact positioning movement without dual structure consisting coarse and fine positionings, higher accuracy air slider studies are conducted a completely frictionless support mechanism using a linear motor and an externally pressurized air bearing. Results are as follows : (1) Temperature rise of 0.3°C, table displacement of 0.16 μm and guide warp of 0.03, μm are achieved by slider guide with adiabatic structure. (2) To reduce cogging force and normal force, coreless and slotless motor is developed. Thrust ripple has reduced to less than 2% of the rated thrust. (3) Maximum pulse velocity of 10 Mpps, acceleration of 3 m/s², 0.2 sec for 15 mm stroke are achieved. (4) Software servo system using DSP is adopted, positioning accuracy of 10 nm are achieved without fine positioning.

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AE signals, which are occurred on friction and wear, have a good correlation with the phenomena of friction and wear. In this paper, the seizure process of journal bearing were measured by A E technique. It was found that A E signals can detect the unusual phenomenon of the bearing condition at in-process and higher sensitivity than that of other monitoring method, such as the measurement of frictional force and frictional temperature. That is based on the following results. (1) The processes of seizure have several different cases, do not always change regularly. (2) But, in the case of generate seizure, AE signals are characterized by the AE frequency spectrum of above 0.5 MHz. (3) Moreover, this characteristic appears much earlier than the seizure. (4) As mentioned above, the measurement of A E signals is effective in the prediction of seizure.

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An automated measurement method of drill wear and chipping is developed for applications to machining centers. Two ITV cameras are used. A global image via the first ITV camera is used to rotate the drill for a major cutting edge to be a central vertical line in each of three detailed images via the second camera. The second camera, in turn, focuses automatically towards a potentially affected small region of the drill, the three detailed images are inputted into a computer, and failed portions are extracted by image processing techniques. One or two dimensional quantities such as wear width, chipping width, and failed portion area are determined successfully together with three dimensional shapes as drill surface contours. Lighting directions are determined in such a way as a diffuse component dominates a specular reflection and the failed portions are more illuminated than normal portions.

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A new method for measuring particle sizes of nanometer (nm) order has been developed using a light-scattering method with Ar⁺ laser. In this study, it was tried to decrease the background noise in the optical instruments, and to do theoretical analysis for signal noise ratio (S/N) with shot noise on a photomultiplier (PMT). Consequently, it was verified theoretically that this measuring method is applicable for detecting the particle of nm order sizes. Furthermore, it was carried out detecting for particles on the surface of raw Si wafer with this measuring system, and it could be detected a voltage signal corresponding to a particle diameter about 20 nm.

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Porous gas bearings show high load capacity and bearing stiffness. Conventional metal sintered porous gas bearings are the surface choked type and there are some difficulties in controlling gas permeability. Recently, porous ceramics with low and homogeneous permeability can be easily obtained and machined with high accuracy without any surface chok-ing. In this paper, analysis of porous ceramic gas bearings are presented and steady state characteristics are calculated for the cases of externally pressurized, self acting, and hybrid type operation. Pressure distribution in porous ceramics is also calculated when the surface is slightly choked to improve pneumatic hammer instability.

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In this paper, bearing performances of gas bearings with double-plane admission are evaluated. It is well known that physical meaning of bearing performances are made clearer by the use of single-plane admission. But they are not practical when used as a machining tool. Therefore, considering the high stiffness and prevention of pneumatic hammer occurrings, each pocket in the exit of the restrictor (inherently compensated effects are included=hybrid restrictor) should be made shallower. The bearing performances (stiffness, damping, and journal center locus) with hybrid restrictor are calculated, and they are also compared with orifice type bearing and inherently compensated bearing. Fllowing conclusions are obtained : (1) Hybrid type of maximum bearing stiffness is 1.4 times as large as inherently compensated and 1.1 times as large as orifices. (2) The clearance where the maximum stiffness is obtained exists in full stable region by using a shallower pocket. (3) As the shaft response characteristics mainly depend on damping magnitude, the pocket depth as large as the operating clearance is desirable.

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In this research, the reduction of the crack due to the grinding of ceramics was investigated by changing the modulus of elasticity of bonding materials of grinding wheels, and as the results, the following conclusion was obtained. (1) The occurrence of crack due to the grinding of ceramics was reduced as the modulus of elasticity E of the bonding materials of grinding wheels decreased. (2) The crack due to the grinding of ceramics reduced its depth of penetration with the decrease in the modulus of elasticity E of the bonding materials of grinding wheels. (3) The decrease in the modulus of elasticity E of bonding materials decreased the size of the cracks due to grinding, and lowered also the rate of crack growth. (4) As the rate of cooling of grinding fluid was larger, the occurrence of the crack due to grinding was promoted, and the cracks became larger.

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In order to develop the unconventional machining method, the stock-removing and machined-surface properties of Si wafer was investigated by making collide obliquely submicron-sized tungsten and its carbide particles with the velocities of about 100 m/s. The results obtained are as follows : (1) The volume removal per hard carbide particle measured is well approximated by an elastic penetration volume introduced from Hertzian impact theory. This suggests that the removal may be caused by cutting action based on ductile shear fracturing of Si. But the depth of cut estimated with relatively soft tungsten particle became of atomic scale smaller than elastic penetration value, and which may be due to severe plastic flow in the particle. (2) The RHEED observation of the machined Si surface whose roughness is of the order of 10 nm suggests the existence of slightly distorted lattice layer. (3) The phenomenological change from Si removal to particle deposition obviously proceeds at particle incident angle beyond 45°. Such a phenomenon is briefly discussed from a viewpoint of particle-energy consumption by measuring the reflection spectra of post-impact particles.

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Microcutting of particle dispersion-hardened alloys are performed with SEM direct observation method. These alloys, hypereutectic Al-Si alloy and Al-Ni binary alloy, include second-phase hard particles in the soft matrix with comparatively rich (Al-Ni) or poor (Al-Si) ductility. Tool wear of carbide tool in the turning of Al-Ni alloy is hardly observed; this indicates that the ductility in the matrix would play an important role to reduce the severe tool wear. Summary of the results are shown below. (1) Compressive load to start the fragmentation of a simple particle in both alloys shows almost the same value. (2) The increas-ing rate of percentage of fractured particles in Al-Ni alloy by the compression test is smaller than that in Al-Si alloy. This can be attributed to the load relaxation to second-phase particles induced by the plastic flow of the matrix. (3) Fragmentation of particles and direct collision of particles with the cutting tool were observed in microcutting of these alloys by SEM direct observation method. (4) Rich ductility of the matrix in Al-Ni alloy would produce the elusion of particles in the case of direct collision of particles with the cutting edge; this indicates that the extent of damage to the cutting edge by particles should be small. (5) Poor ductility of the matrix in Al-Si alloy causes higher frequency of the mechanical scratching action by particles for tool flank.

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Surface roughness and tool wear was investigated when low-carbon resulfurized free machin-ing steel was cut by means of either plunge-machining or ordinary turning with a partially stabilized zirconia ceramic tool (PSZ). Moreover, the cutting performance of the PSZ tool was compared with that of some conventional tools. (1) Small amount of manganese sulfide inclu-sions in steel has trends toward to adhesion to the PSZ tool, resulting in the formation of MnS layer on the tool with a thickness of 2-3 μm. (2) The MnS layer seems to have a roll of a kind of lubricant, and restricts the formation of built-up edge and wearing the tool. (3) The perfor-mance of the PSZ tool is superior to both a high-speed steel tool and a sintered carbide tool with respect to surface roughness and tool wear.

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This paper deals with the cutting mechanism and performance of end mills with different helix angles on adjacent teeth. The results are as follows. (1) Cutting mechanism of end mills with different helix angles on adjacent teeth is analyzed geometrically. And also chip area are calculated and its characteristic are shown. (2) Evaluated value for cutting performance of cutter is defined by mean and standared deviation of expected cutting force curve, and the values by cutters are compared with one anothor. (3) Under the experimental conditions, cutting performance of cutters with combination of 35° to 45° helix angles are better than another cutters, and optimum combination of helix angle is 40°-40°. (4) It is shown that end mills with different helix angles, by only a few degrees, on adjacent teeth reduce the deviation of chip area greatly. So these cutters are able to expect to control chatter in end milling.

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The cubic boron nitride films have been prepared by newly developed CO₂ laser PVD process assisted with simultaneous irradiation of nitrogen ion accelerated by a Kaufman type ion source. The CO₂ laser beam was focused and irradiated onto the peripheral surface of a rotating sintered hexagonal boron nitride (hBN) ring and the vapor was deposited on a substrate. The films were characterized by ESCA, thin film X-ray Diffraction, AES, IR spectroscopy and SEM. The composition ratio N/B of the prepared film has neared 1 at an accelerating voltage over 1 kV. Cubic boron nitride was clearly indentified at nitrogen ion accelerating voltage over 0.5 kV. The cBN rich films were found to have extremely high Knoop hardness of 3 800-4 600 kgf/ mm² and high wear-resistance against Ni-Mo steel.

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In this study, the forecast for tool life using an acoustic emission was investigated. The discriminative level setting system was employed by developing the acoustic emission sensor, preparing the software for real time analysis and adding the floating function. The results indicated that : Addition of the floating function to take in stably the event count and oscillation count gave out a satisfactory result. Discrimination by the minimum duration to cancel noise signals removed the influence of cutting fluid and collapse of chips. Judgment of tool life with a method to quantify by the ratio of the event count and oscillation count per unit time allowed to forecast tool life very accurately. From the above transactions, the evaluating method to quantify tool life by the ratio of the event count and oscillation count was found effective.

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Scratching experiments have been carried out on ZrO₂, Al₂O₃, Si₃ N₄ and SiC materials by using the diamond tool which consists of four pyramidal shape diamonds. It is found that in Al₂0₃, Si₃N₄ and SiC radial cracks appear below the grooves scratched by inner two point diamonds, where the material is constrained between other two point diamonds. Only in the case of SiC, as the radial cracks penetrate towards other grooves from the inner two grooves, surface portions are removed. Therefore no microcracks are observed. It is also found that microcrack clusters exist below the grooves of Al₂O₃ and Si₃N₄. In ZrO₂, cracks occurred only near the surface of specimen, it is observed that no cracks penetrate towards the inside of material like other materials.

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This paper describes a method of generation of the surface defined with contour and sectional curves. The method is a modification of the least curvature error method which was developed for the generation of the surface defined with contour curves only. The generated surface is expressed as a whole in a parametric bicubic spline surface, and it has continuous cross curvature on the sectional curves. The method requires target second derivatives at all knot points, and the quality of shape of the surface depends on these derivatives. Therefore giving consideration to the characteristics of surface is desirable when deciding target derivatives. However some examples show that even simply interpolated target derivatives are able to generate a low-error surface.

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