This paper describes on a new method of the positioning with five adjacent lines in a linear scale and its experiment and result by using the new designed photoelectric microscope in order to reduce the errors of line positions in a scale and to use in higher accuracy. The microscope which has a mask with five slits arranged in equal interval at the image plane of the objective carries out the way above optically. As the result of experiment, the short period error and the random error in the scale are reduced and the special large errors are excluded, then the accuracy of the scale can be improved both to 1μm from 5μm level by using this method and from 20 μm level by using together with the existing automatic compensational way for scale errors.
This paper presents theoretical and experimental characteristics of a self-acting step-groove gas bearing. This bearing has some axial grooves on its surface. However, its configuration is much simpler than the conventional spiral groove, so it is applicable to use in many precision apparatus, like a laser beam scanner. When a rotor in the bearing rotates, compressibility number Λ: 6μω/ Pα(R/ C)2 increases and hydrodynamic pressure is generated on the groove parts. Here, μ : coefficient of gas viscosity, ω; rotor angular velocity, Pα ; atmosphere pressure, R; rotor radius, C; bearing clearance. The configuration and number of grooves affect hydrodynamic pressure, bearing load carrying capacity and stability. When eccentricity ε and Λ are given, an appropriate groove configuration is determined. Generally, in small Λ and ε, the bearing with small groove depth gives much higher load carrying capacity and stability. However, in large Λ and ε, large groove depth gives higher stability than small groove depth. The laser beam scanner, which uses this bearing and the newly designed thrust magnetic bearing can rotate less than 1.0 μm run out and 0.003% revolution fluctuation at 12000 rpm.
About slider-crank mechanisms with clearances, a dynamic design method has been discussed to determine directly the optimum shapes of connecting rods to prevent separations and collisions between pairing elements, after showing that the separations and collisions can be predicted simply from an exciting force of a model vibratory system with a mass, spring and dashpot which is derived from equations of motion of mechanisms with clearances. The results are as follows : (1) A dynamic analysis of slider-crank mechanisms with clearances has been carried out, the results of which are coincident with experimental ones. (2) A vibratory model has been derived from the equations of motion of slider-crank mechanisms with clearances. Separations between pairing elements have been shown not to occur if the exciting force of the model is constant with respect to time. (3) In order to obtain mechanisms with good dynamic performances, the shapes of their connecting rods have been determined by Simplex method with objective functions derived from the conditions where the above exciting forces become constant. No separations of pairing elements have been confirmed to occur theoretically and experimentally in the mechanisms with the optimized connecting rods.
Recently, as methods to control the tightening force in bolted joints, the torque gradient control method and the turn of nut method in which bolts are tighten in plastic region attract notice. However, the behavior of bolted joints subjected to external load after preload is not sufficiently clear. Therefore, some experimental studies on the behavior of the bolted joints in elastic region and in plastic region are carried out. A new extensometer and a bolted joint model are trially designed and produced. Then direct-tension test of bolt, torqued-tension test and direct-tension-after-torqued-tension test of bolted joints are carried out. The main conclusions are summarized as follows : (1) The axial tension-elongation curve of the bolt in the bolted joint under the external axial loading comes near that in the simple bolt. (2) New tightening diagrams of bolted joints in elastic region and in plastic region are presented. (3) The new torque control method in which the maximum axial tension of about 0.8·Fy (Fy; yielding load or proof load) can be introduced by tightening, is presented. (4) The new design system of the bolted joint on the basis of (2) and (3) should be constructed.
When the values of coordinates and gradients at some points on a work tooth profile are given, we can calculate the hob tooth profile analytically. In this report, the calculating method of allowable angles for the circumferential form relief and the side relief to the given hob tooth profile is described. By this method, we can know easily whether sufficient relief angles can be obtained or not.
The friction and wear properties of pure and bronze filled polyacetals (POM) have been studied sliding against a carbon steel surface (slider) under unlubricated conditions. Spherical, irregular and waterdroplike particles of 53 μm and below were used as the fillers. The electron microscopic examination of the frictional surfaces was used to evaluate the role of the filler materials. The results obtained were as follows : (1) The coefficient of friction of bronze filled POM was slightly higher than that of pure POM. The wear of bronze filled POM was approximately one half of that of pure POM. Waterdroplike bronze filled POM had the best wear resistance of all specimens at high pressure and velocity. (2) Owing to the effect of fillers, the pv limit of bronze filled POM was remarkably improved. The pv limit of waterdroplike bronze filled POM was approximately three times higher than that of pure POM. (3) Waterdroplike particles showed the best effect of increasing the load-supporting action of all filler shapes.
This paper presents a method in which a high speed rotating silicon wafer is ground by continuous infeed of cup type grinding wheel. Some grinding results of silicon wafers by this method are compared with those of conventional face grinding method and creep feed face grinding method. By these experiments, following results are obtained on silicon wafer grinding : (1) Silicon wafer can be ground normally under the condition of zero speed at its center and high speed such as 314 m/min at its periphery. (2) Surface roughness and its variation are equal to or less than those of conventional face grinding and creep feed face grinding. (3) Straightness of ground surface is remarkably improved compared with that of conventional face grinding and creep feed face grinding.
Usually, a pair of cone centers have been used for supporting the workpiece in cylindrical grindings. Then, the roundness of ground surface is influenced by the form errors of cone centers and center holes, misalignments and lubrication. Although it costs much time and money, the center holes must be ground or lapped for the precise cylindrical grinding. The purpose of this paper is to establish a grinding method which makes precise cylinders easily and inexpensively. In the experimental apparatus, two holders press the workpiece through each balls. Both the holders and the workpiece have center holes. The experiments were conducted under following two conditions. First, the balls were fixed on the holder. Second, the balls were fixed on the workpiece. The latter was better than the former to finish the accurate cylinder. In the latter condition, 0.5μm out-of-roundness of the ground surface was obtained with the precise balls of0.7μm out-of-roundness.
Cylindrical plunge grinding process and chip formation mechanism of normally sintered and partially stabilized zirconia are experimentally investigated with bronze bond diamond wheel, analyzing grinding force, surface roughness, wheel wear, grinding chips and so on. A new technique for better surface finish is introduced in which readjustment truing with an impregnated dresser is performed after dressing of diamond wheel with GC wheel. Main conclusions obtained in this study are as follows : (1) In a cylindrical plunge grinding cycle of partially stabilized zirconia with bronze bond diamond wheel, there are three distinct grinding states such as spark-in, steady and spark-out just as in grinding metallic materials. (2) Readjustment truing technique leads to better surface finish and higher grinding force as compared with those in dressing with GC wheel. (3) Grinding force increases with an increase of setting depth of cut, while surface roughness is hardly influenced by setting depth of cut. (4) Chip formation in grinding partially stabilized zirconia is primarily predominated by plastic deformation as in grinding metals.
Machining of several kinds of resulfurized and ordinary carbon steels under high cutting speed was investigated in order to reveal the effect of inclusions and deoxidation practices on tool wear. Also, the difference of machinability between the continuous casted and ingot casted resulfurized steels was examined. The results obtained were as follows : (1) In machining of the continuous and ingot casted resulfurized steels the difference of machinability is not certainty and it may be reversed with the kind of tool material used. (2) In comparision of the tool wear between resulfurized and regular steels the crater depth is closely related to the deposited layer on rake face, but the flank wear of carbide tool P 10 in machining resulfurized steels is always smaller than that of regular steels. (3) Increase of the content of oxide inclusions (SiO2, Al2O3, etc.) in steels generally causes the increase of tool wear by abrasive, but when these oxides are controlled to form a stable protective layer on the tool face, the tool wear can be suppressed.
In this paper, the elliptic ball-end-mill, whose characteristics are that the re-grinding operation is simple and that the same cutting edge shape is obtained by the re-grinding operation, is proposed. The elliptic ball-end-mill is formed by cutting an elliptic column at the suitable angle, and the cutting edge consists of the first cutting edge which has an elliptic surface as a rake face and the second cutting edge which has a cross section of an elliptic column as rake face. And, the forming method of the cutting edge shape is established. Then, the most suitable cutting edge shape of the elliptic ball-end-mill to minimize the cutting force is that the part of 40% of the tool radius from the top of the tool is composed by the first cutting edge, that the rest is composed by the second cutting edge, and that the cutting angle of the elliptic column is about 50 degrees.
Straight grinding fluids have been shown to have high performance but were not used in actual grinding because of the high possibility of fire hazards and thermal distortion of work. A dual-fluid supply method has been developed by the authors that makes such grinding fluids practically applicable. The method consists of supplying a straight grinding fluid from a Makitsuke nozzle (that stick the grinding fluid to the wheel surface) and, at the same time, directing a coolant on the underside of workpiece. The method has been applied successfully in high efficiency grinding (1200 mm2/min) using a CBN wheel, with the result of a grinding performance about 5 times better than that obtainable by the conventional method.
Analytical results of early fracture and tool life based on fracture mechanics were compared with experimental results in interrupted cutting. The stress intensity factor was calculated by a finite element method using a cutting tool model with an appropriately introduced crack. Calculated values of stress intensity factor, at which the early fracture occurred, was made a comparison with the fracture toughness of tungsten carbide tools and ceramic tool. The tool life of tungsten carbide P 20 was also calculated using the analytical method proposed in the previous report, and the calculated values were found to be consistent with experimental results. The cutting tool performance for the early fracture and the tool life increases in the main with increasing the fracture toughness. These comparisons suggest that the brittle failure of cutting tools can be analytically estimated by the application of the fracture mechanics concept.
The elimination process of the eccentricity of a cylindrical workpiece as a basic model of the shape error was experimentally analyzed. The results may be summarized as follows : In the one pass traverse grinding, a limit residual shape error is in existence. The limit value increases as initial shape error grows larger. When total setting depth of wheel is a constant, the residual shape error is reduced in size by decreasing the setting depth per traverse, and by increasing the number of traverse. In order to eliminate the effect of initial shape error by the spark-out grinding, it is necessary to establish the setting depth of wheel over the sum of initial shape error in size and a limit residual stock removal.
A new truing technique with the cup-truer proposed in the previous paper has proved effective on diamond vitrified wheels. In this paper the performance of the cup-truer in truing peripheral wheels is examined in detail. The main results obtained are as follows : (1) The traverse feed of the cup-truer across a diamond wheel produces a tapered periphery of the wheel. This may be the same for any other kind of tool in so far as it is used in a similar manner. (2) Plungecut truing, i. e. the truing process with a reciprocating feed without a cross-feed of a cup-truer, provides a straight, taper-free periphery of the wheel by adjusting the cup-truer axis, perpendicularly to the grinder table. By tilting the cup-truer axis, moreover, tapered peripheral diamond wheels also can be trued. (3) In plunge-cut truing the smaller wheel speed or the larger truer feed speed gives the greater truing ratio. Truer rotating speed does not influence the truing ratio appreciably. (4) Excessive wheel speed in truing makes diamond abrasive edges dull.
Transient cutting temperature in interrupt cutting has been studied with the aim to evaluate the thermal crack resistivity of the cutting tool materials. Transient temperature distribution inside the tool, which governs thermal stresses and consequently thermal cracks, has been theoretically analyzed and formulated to the simple algebraic equation. The calculated transient temperatures of the tool surface by this equation have the good agreements with those obtained experimentally.