A computer-controlled positioning turntable has been developed for microfabrication applications. A newly designed highly accurate positioning turntable is driven by the "inchworm" function using piezoelectric actuators. The positioning turntable can move for a long stroke with excellent positioning accuracy. All parts constructing the positioning turntable can be made of nonmagnetic materials. The turntable can also be used in a vacuum environment. The positioning turntable travel is π/2 radians. The angular velocity can be controlled up to 3.2×10-2 rad/s by changing the "inchworm" function stepping rate. Average value for and standard deviation in moving resolution are 1.67×10-7 rad (0.035 arcsec) and 7.05×10-8 rad (0.015 arcsec), respectively. A less than 4.8×10-6 rad (0.1 arcsec) positioning accuracy has been achieved.
In this paper, a method for evaluating the strength of plastics bolt under tensile impact load is considered, for the purpose of obtaining available data for the strength design of the bolted joint with the plastics bolt. First, a testing machine, which enables to measure the tensile load acting on the bolt and the energy absorbed into it during tensile impact whether the bolt is broken or not, is built as a trial because it is impossible to evaluate these values by means of the standardized testing methods. Second, by means of this machine, the characteristic values for generalizing the strength of the bolt under impact load are considered varying the nominal diameter of the bolt, fastened length of the bolted joint and impact energy. As the result, obtained conclusions are as follows: (1) The maximum tensile load induced to the bolt by impact can be generalized by use of the impact energy per unit volume of the bolt and the maximum tensile stress, in spite of the nominal diameters of the bolt and fastened lengths of bolted joints. (2) The energy absorbed into the bolt can be also generalized by use of both the impact energy and the absorbed energy per unit volume of the bolt as far as the necking is not occurred in the bolt.
The design of an ultraprecision displacement sensor with subnanometer resolution is proposed for the use of ultraprecision technologies. The principle of the sensor is based on the high-sensitive detection of power change at a specific point in the light reflected from the object surface which is subject to a small displacement. The sensor consists of the single light source, the reflective object and reference surfaces, the optical fiber bundles for transmission of the illuminating and the reflected light and the photodiodes setup. In operation, the object and the reference surfaces are illuminated by the light transmitted through the optical fiber bundles from the single light source. Then, the reflected light from both surfaces are transmitted through the other optical fiber bundles to two separated but equivalent photodiodes respectively. By using the differential amplifier, the diodes enable to give a high-sensitive displacement signal which is included in the total signal of the reflected light. The sensor proposed here has some distinctive features such as the non-contact measurement, the high resolution of 0.5nm, the wide working range of about 30μm within the 5% linearity and the sufficient stability of 1nm in 20 seconds for specific research purposes.
This paper presents a reflection device to measure three components of angular alignment, that is, pitch, yaw and roll with same sensitivity and simultaneity. Pitch and yaw components can be measured by usual arrangement of autocollimator, while roll component by the present device having a reflection mirror hung by thin leaf spring. The principle of the device is clarified by the analysis of the direction cosine. As one of practical problems of the device, the deflection of the spring under rolling is analized. A magnetic damper is used and its effect is checked in order to control a continuous and small vibration of the mirror. The following results are obtained by a few experiments: (1) The three components can be distinguished in the field of view of an autocollimator. (2) The sensitivity and linearity of the device is checked under rolling, changing a few parameters of length and thickness of the spring. The correction and calibration methods are also mentioned and determined. (3) The magnetic damper controls small vibration to be a noise of the reflection mirror and decreases it to 1/20.
The study presents the development of an automatic measurement system of machining errors of workpieces, on the same machine, without detaching them, and the evaluation of machining errors. A machined workpiece on a personal computer based DNC lathe is subjected to inspection by an electric micrometer mounted on the tool post in substitution for the cutting tool. To measure the deviation from the ideal dimension of workpieces automatically, the electric micrometer is moved along the surface of the workpiece by NC instructions for measurement in co-operation with the automatic programming system. Measured machining errors are compared with the thermal expansion of tool affecting the machining accuracy chiefly, and formulated as a function of cutting conditions.
In this paper the structure is shown of a newly designed apparatus for experimental study on magnetic bearings. A common-type totally active magnetic bearing is composed of an axial bearing, two radial bearings and motor stator. Since a magnetic bearing system is usually designed to be fit for a certain use, for an example, grinding or vacuum pumping and to operate under the special conditions, the arrangement of the components is fixed. Such a system, however, tends to lack in flexibility as an experimental setup used for various purposes. In the developed apparatus each component of a magnetic bearing forms a unit. Since units can be combined and arranged in various ways according to trying experiments, it can be adapted for many applications, for example, an experimental study on control of a flexible shaft. In this research the apparatus is used to demonstrate the ability of compensation for unbalance, which has been proposed by the authors, to prevent the suspended rotor from whirling due to unbalance by cancelling unbalance forces by electromagnetic forces.
Use of linear air slides is increasing presently because their friction is low and motion straightness errors are small. But it is difficult to drive them without the influence resulting from driving mechanisms. A steel belt is often used for driving them owing to its inexpensiveness and mechanical simplicity. The goal of this report is to clarify how a steel belt driving mechanism for an air slide influences its motion accuracy. The driving mechanism delt with is a two-pulley system and the motion accuracy is considered in five directions such as vertical and horizontal positions, and pitch, yaw and roll angles. First the driving mechanism is removed from the slide and its free motion accuracy is measured as the standard accuracy. Then the motion accuracy is measured of the slide driven by the belt mechanism and change in the accuracy relative to the standard is checked. Experimental results show that the belt drive mechanism scarecely causes change in the accuracy whether or not misalignment of the belt exists, which agrees well with calculated results.
This paper relates to the fiber formation region in Chatter Machining method in which the effects of various manufacturing conditions are experimentally investigated and their causes are discussed on the basis of the mechanism of fiber formation. It is confirmed that the conditions such as adequate tool rigidity, additional weight on the lower end of the elastic tool, increase of relief angle, keen cutting edge as well as high cutting speed should be satisfied to obtain wider fiber formation region, considering the influence of manufacturing conditions on the allowable feed rate, dynamic behavior of cutting edge and sizes of chatter marks. Finally, it is concluded that deep penetration of cutting ege into the material surface and appropriate phase lag between the inner and outer modulation of cutting edge are essential to achieve wider fiber formation region. These results are also explained by computer simulation.
Parameters which can evaluate the macroscopic thermal crack resistivity of cutting tool materials, have been studied in this report. The resistivity parameters and thermal stresses inside the tool are derived from the equation which was derived in the previous report and gives the transient cutting temperatures in interrupt cutting. High speed interrupt cutting tests of plain carbon steel using cutting tools with different properties were conducted and the numbers of interrupt cutting until thermal crack generation were examined. The experimentally obtained numbers are proportional to their own resistivity parameters.
For the purpose of obtaining practical guidelines for controlling the vibration that produces on the plunge-cut ground surface the local variations of the light reflectivity, the mechanism by which the dynamic unbalance of the rotating grinding wheel generates the dynamic variation of the instantaneous stock removal and hence the onset of the grinding vibration has been studied by theoretical analysis as well as grinding experiments. Experiments have also been carried out to optimize the method of varying the rotational speed of the wheel, of which effect was demonstrated by a former study. By monitoring the oscillation of the machine body at the frequency of the wheel rotation, it is first recommended to adjust the wheel balance to minimize the monitored oscillation prior to the dressing operation. The subsequent grinding operation has to be carried out without introducing any balance adjustment and wheel speed variation after the dressing. Effect of the balance adjust procedure in suppressing the grinding vibration is further enhanced by introducing the wheel speed variation. According to grinding test results comparing the rectangular and triangular patterns of the wheel speed variation, the former has been found more effective, which at a ±10% range variation for 4 minutes period seems to result in an optimum effect for practice.
The carbide tool for screw thread turning has been used widely in NC lathe. However, few studies have been performed about tool wear of the carbide tool for screw thread turning and the effects of tool wear on an accuracy of a turned screw thread. The present paper deals with the effects of tool wear in screw thread turning, and describes a setting method of a criterion for tool wear. The results obtained are as follows. (1) The tool wear brings the reductions of the front cutting edge and the side cutting edges. These reductions of the cutting edges decrease in the accuracy of a turned screw thread. (2) The irregularities of the same number of the groove wear appear on the flank of a turned screw thread. (3) Allowable flank wear lands are derived from the tolerance system for metric screw threads, and a criterion for tool wear in screw thread turning is proposed by means of the cutting force ratio. By making use of these results, a method for detection of tool wear and failure during turning screw thread is proposed. It is confirmed that the monitoring system is reliable.
The paper is concerned with the finishing process using magnetic fluid, and it aims at obtaining a high removal rate in the finishing process whose abrasives are supported by liquid. In the case of using magnetic fluid as polishing fluid, the effect of ferrite particles and surface active agents which contained in magnetic fluid on removability needs to be investigated. An experiment of conventional finish using magnetic fluid as polishing fluid is performed where polyurethan polishing pad is used. The removal rate by using magnetic fluid becomes lower than that by using water in this process, because high viscosity of magnetic fluid cause better lubrication between workpiece and abrasives. Next, a few experiments of the affinity between magnetic fluid and abrasives are carried out. The strong affinity is undesirable because it causes the good lubrication too. On the other hand, in the case of finishing process which abrasives are floating on the magnetic fluid, high viscosity should be desirable because it strengthens the supporting force of abrasives. Several experiments of polishing applying the magnetic levita-tion make it clear that the finishing characteristics are affected by the magnetic field strength and viscosity of the mixture of magnetic fluid and abrasives.
The mechanical vibration often prevents from acheiving higher performance of an electromechanical control system which consists of closed loop electrical part and structural part. A new sensitivity analysis is developed in order to take account the amplitude and phase change of the total control system with respect to the mass or stiffness of the structural part. The modal analysis is used to determine the modal parameters of the structural part and then the servo analysis describes the closed loop characteristics. After identifying these parameters, the amplitude and phase sensitivity can be calculated in the function of frequency. A numerical simulation reveals that the proposed method can predict correct sensitivity. Then a simple electro-mechanical control system is manufactured and the sensitivity analysis is applied to confirm the effectiveness of the method.
In many computer simulations such as assembly simulations, robot simulations and NC simulations, it is necessary to investigate interference among objects. Although many kinds of methods of interference detection have been developed until now, it is not sufficient for those methods to treat the objects which touch on their faces. This paper presents the method to recognize the interference between two objects modeled in computer. There are two types of interferences, a collision in volume and a touch on faces. For identifying the state of touch on faces, the objects must be modeled not approximately like polyhedral models but exactly. A dual expression by both CSG(Constructive Solid Geometry) and B-Reps(Boundary Representa-tions) is adopted for the purpose of determining the interferences. Three steps are introduced to execute the interference recognition: (1) The dual expression is constructed by exact conversion from CSG to B-Reps. (2) The characters of edges and faces are classified and formulated. (3) The algorithms are developed to generate the data to which the classifying formulations in the second step can be applied. Finally, a typical system to demonstrate this method with meaningful results is also mentioned.
The second paper describes the basic algorithms to obtain shaded pictures on CRT display from TIPS-1 geometric database by interactive operation. However, from the practical point of view, the algorithms in the second paper are not enough with respect to the processing time and required storage of the data in the CPU memory. In the first half of this paper, some techniques for further improvement in the algorithms in the second paper are discussed. And then, in the latter half of this paper, a methodology of the generation of line-drawings from the described shaded pictures is presented. line-drawing are composed of the contour and profile edges of the object shape which are extracted from the described shaded pictures. And, line-drawings require less processing time to transmit the display data from computer to graphic display, because the data of line-drawings are less than those of shaded pictures. Therefore, it is important and desirable to make a system that has the capability of getting not only shaded pictures but also line-drawings.
In this study, we investigate the mis-selection of automobile assembly parts. The mis-assembly results are analyzed by the multivariative quantification method I. It is found that three factors, namely, the number of kinds of a part, worker's experience and instructions for part's use are essential for mis-assembly occurrence. Based on these observations, a new parts selecting instruction system is proposed to prevent the mis-assembly occurrence. The mis-assembly occurrence ratio with the new system shows a significant decrease as predicted by the analysis.
This paper presents a new forecasting method of service parts demands by taking into consideration product life and part failure characteristics in addition to the production volume at each period. The new method also makes it possible to estimate the product still in use quantity based on the service parts demands in the past.