The purpose of this paper is to properly plan the preventive maintenance schedules of multi elevators and optimize the number of maintenance personnel so as to minimize the total cost of the maintenance cost composed of labor cost and parts cost, and the quality cost, namely the loss to be incurred when an elevator breaks down. The method is presented to compose the optimal preventive maintenance schedules on a long-term basis by rescheduling the contents of schedules dynamically and flexibly in accordance with ever-changing maintenance conditions, with taking the possibility of the future failure occurrence into consideration. From numerical experiments, the validity of the presented procedure for planning the preventive maintenance schedules and the effectiveness of considering the possibility of the future failure occurrence in planning the schedules are shown, and the optimal number of maintenance personnel can be determined.
The fritting of thin oxide on metal surface is indispensable to realize micromachined probe cards, because each microprobe cannot endure the force required to break the oxide on the surface of IC pads mechanically. In order to clarify the force required for fritting-contact make, the relationship between contact forces and the fritting has been investigated using an atomic force microscope (AFM) system and micromachined cantilever probes with a pyramidal tip. The following results are obtained on the fritting between electroplated Au tip and Al or Cu films: (1) A stable low-resistance contact to Al and Cu films can be obtained without applying contact forces larger than 30μN, when the applied voltage is larger than 15V. (2) Then the adhesion forces between the probe and films are less than 30μN. (3) The fritting contact of Cu film is easily obtained with low contact force and low applied voltage compared to that of Al film. (4) Contact resistance decreases with increasing the fritting current. In addition, it is concluded that probe cards consisting of micromachined cantilevers can be applied to the test of peripheral pad configuration IC with the pad pitch of 20μm, in consequence of simple calculations.
This paper proposes spiral grooved aerodynamic thrust bearings functioning as a viscous vacuum pump for a laser scanner motor in order to reduce the windage power loss of a polygon mirror. The proposed bearing can pump out air within the scanner housing by using the pumping effect of the spiral-grooved thrust bearing, and reduce the inner pressure of the housing. The pumping performances and the static characteristics of the proposed bearings are investigated numerically and experimentally. It was consequently found that the proposed bearing can reduce the inner pressure of the housing to less than 0.01 MPa and have the sufficient load carrying capacity to support the rotating shaft.
In Toyota body assembly line we introduced the Flexible Body Line since 1985. This line has the character that consists of 300 robots, and the robot breakdown causes the enormous damage for the product line. As the result the line availability depends upon the robot reliability in particular. Therefore in order to improve the robot reliability, we tried to apply the statistical method and proved the effectiveness. At first we investigated the failure field data and clarified the failure mode. After that we designed reliability line model for the requirement of Robot MTBF. In addition we developed the estimation method for the mechanical parts life according to the each robot's motion. Consequently we standarized the overhall specification and reduced the life cost of the robot. Owing to these activity, we attached the high reliability of robot and introduced many robots into the line.
In-process measurement of surface roughness is an important factor in automatic precise polishing. The authors have proposed a new optical method to evaluate roughness of polished metallic surface. By applying a Torrance-Sparrow model, it is theoretically shown that the variance of the intensity of the reflected light is given as the summation of that of the light source and the rms value of the surface roughness. In order to insure that the proposed method is effective, some experiments have been carried out. The test pieces were made by brass. From the results of the experiments, the measured surface roughness agree quite well with the root-mean-square roughness represented in Rq (roughness in root mean square) measured by a stylus roughness meter.
Two driving methods based on the principle of 'walking drive' are summarized and compared in the present research. The predetermined displacement patterns are applied to the piezoelectric actuators in one method, and the patterns are generated in real time in the other method. Their characteristics are clarified, e.g. the former method is easier to implement while the latter can reduce the number of actuators. A compact XTθ table is developed based on the latter method. The developed XYθ table has unique characteristics such as compactness, ultra-fine positioning resolution, slow and smooth motion, long stroke, frictionless drive, no use of any conventional guides, no need to stack up multiple tables, no need for lubricant, and high stiffness. Furthermore, the developed table can be driven in the vertical plane, because the table is attached to the driving parts by a permanent magnet. A position feedback controller is developed with capacitive sensors, and some positioning experiments are carried out. The experiments show that the system has a fine positioning resolution of about 30nm which corresponds to the noise level of the sensors.
A new measurement method at two-solution interface with image processing has been proposed. The interface lies at the boundary between two fluids in the chemical plant facilities. The method is based on the phenomenon that the interface drifts up and down in operation. An algorithm to measure the interface by using interframe difference is shown. The subtraction image is compared with the typical models to determine the interface level. The method is applied to the measurement at the interface of oily water separating tank in the plant, and satisfactory results are obtained.
This paper proposed a method for image template matching that is robust to the occlusion of a target image area. A template image is separated into local block areas and the normalized correlation rates are calculated in all block areas. Only partial block areas that may be useful for matching are selected according to the thresholds for the normalized correlation rates in all block areas that are set through the template matching using the reference images. The experimental results show that the proposed method was robust to the occlusion of the target image in comparison with the conventional methods because it can search the target image area successfully even if the 90% of the target image area is occluded.
An extension of the ICP (Iterative Closest Point) registration algorithm based on modified M-estimation for realization of robustness against outlying gross noise in two point data sets. The proposed algorithm is utilized to obtain a transformation consisting of rotation and translation parameters in order to perform the best fit between the data sets. An objective function which includes independent residual components for each of xyz coordinates is defined to evaluate the fit between the data sets, taking account of distribution of the outlying noise, which occurs due to occlusion, shadowing, or highlighting in measurement. The approach is based on modifid M-estimation through an iterative procedure for optimization of the transform for correspondence. Some fundamental experiments utilizing real data of 2D and 3D measurement show effectiveness of the proposed method.
The ultimate goal of this project is to develop a manipulation system enabling unskilled operators to deal with objects in micron or sub-micron size at an environment of scanning electron microscope (SEM). Described in this paper are the results achieved in the first phase, which is focused on conceptual design, prototype development of a twin-arm micro-fabrication system, and its performance evaluation at a number of field tests. The system is modularized into the manipulation unit, the control unit and man-machine interface. The manipulation unit is further comprised of a twin-arm manipulator and a specimen stage driven by PZT actuators and magnifier elements with three degrees of freedom. The control unit provides a two-way communication capability that delivers force and visual information to the operator, and at the same time to interpret the movement instruction to an appropriate speed and distance for the arm to match the SEM magnification. The image processing also makes it available to automatically track an arbitrarily shaped object within the SEM scope and to generate the tool path. The man-machine interface, equipped with force feedback control, synchronizes the movements between the joysticks (input tool) and manipulator arms and offers the operator the intuitive feelings of contact and resistance. Absorbing the mechanical/optical errors by above-mentioned functions, the system allows the operator to concurrently conduct fabrication and observation without paying much attention to the changes in magnification and other operational conditions.
CMP has now been adopted not only for ILD and W-plug, but also for Cu metal and STI. In the STI CMP process, the wafer has some defined waviness, and it has recently been reported that this waviness may affect the STI CMP yield. The principle purpose of CMP is to planarize relatively with larger scale than small topography. Therefore, there may be a range of wafer topography in which the STI pattern may be over polished, depending on its peak-to-valley and frequency. The range and dishing performance of STI are calculated based on step height performance, which is in turn calculated by FEM. In this analysis, CMP is defined as four types of regions; the step height region in which the planarization performance of step height reduction is required, the uniform material region in which uniform polish is required, the non-uniform material region in which the planarization performance of dishing and erosion reduction is required and the substrate region in which defect reduction is required. The allowable peak-to-valley value and its frequency are calculated. It has also been reported that slurry selectivity can decrease this effect, together with disadvantage.
In this paper, the proposed model for cutting forces during end milling of hardened steel is verified for its general usefulness by applying this model to the extended cutting conditions and other applications. The cutting conditions discussed here include concave contour cuttings with a small radius compared to that of the end mill. For this purpose, the operability region by two variables of the arc length of cutting engagement (L) and the maximum undeformed chip thickness(tm) is divided into a few regions of interest which correspond to the cutting conditions geometrically. The control of cutting forces in profile end milling using quadratic polynomials obtained in each region based on response surface methodology was fairly effective. Furthermore, this prediction model was applied for the case of transitional sections of tool paths where the cutting force changes rapidly with the change of feed rate and geometrical conditions, and it was found that the prediction and control of cutting forces was also possible for this problem.
Recently, electrical discharge machining (EDM) has been applied to micro processing. A thin electrode less than 0.1 mm in diameter has been used for the micro EDM. In conventional micro EDM, minute energy is supplied to the gap region for micro removal machining. In this study, we carried out some experiments on single discharge machining with thin electrode. The value of discharge current was selected up to 50A as the machining condition. The electrode wear length was measured for several pulse durations. As a result, we found out the electrode became thinner than original diameters at the edge portion under pulse duration of several hundred μs in a single discharge. A needle of 35μm in diameter and 300μm length can be made instantaneously from a tungsten wire of 0.125mm in diameter. Using a thin electrode, micro drilling could be performed on the machine. The rapid thin electrode production mechanisms are discussed taking into consideration of electromagnetic force, electrostatic force and plasma jets flow.
Silicon (Si)-molecular beam epitaxy (MBE) generated many micro structures such as steps or nuclei, these wall faces of which were directed to some specific crystal orientations in the horizontal plane. Namely, it was indicated that Si molecules were anisotropically grown along with atomic steps by MBE. In this present paper, the crystal anisotropy of epitaxial growth was carefully investigated. As it can be considered that the anisotropy originates in the dangling bond arrangement in the atomic step, these generated micro structures have been analyzed by a newly defined parameter, "anisotropic factor", as a function of dangling bonds density and their direction cosine in the atomic step. As a result of the analysis, it was clarified that the anisotropic factor became local minimum in these specific crystal orientations observed on generated micro structures. It seems that 2-dimensional nucleus or step composing micro structure tends to be surrounded by some atomic steps, these orientations of which have local minimum an isotropic factor. The growth rate of atomic step can be expressed by anisoptropic factor, namely, the lower anisoptropic factor make the growth rate of atomic step relatively slower. In addition to this, It was clarified that the anisotropy of epitaxial growth don't depend on the crystal structure of bulk but that of reconstructed surface.
Carbide-tipped drills having various shapes of main cutting edges, and circular or straight cutting edges or non-cutting zone at the drill center have been manufactured and widely used in recent years. In order to compare the cutting phenomena with these drills, the tool angles such as inclination angle and normal rake angle along the cutting edge, which control the cutting force and chip formation, are discussed. In addition. a cutting model and energy method. in which elemental chip at each point on the cutting edge is described by simple shear plane oblique cutting model and the condition of side-curl of the chip is considered. is extended to drilling with the drills. In the analysis, it is assumed that the chip produced with whole cutting edge consisting of the main cutting edge and the cutting edge at the drill center can be expanded to be a plane. Two cases for chip separating or no chip separating at the junction of the main cutting edge and the cutting edge at the drill center are treated and discussed. Predicted result shows that Stabler's chip flow rule does not hold for the curved cutting edge drills.
This paper deals with the vertical striped pattern formed on the ground surface by high-reciprocation grinding. The high-reciprocation grinding is characterized by the high-speed motion of work table reciprocation, and has become of major interest lately as a new way of high quality and efficiency machining in the production of the punch for the IC lead frames. On the ground surface, the striped pattern appears in the direction perpendicular to the direction of work table reciprocation, and the pattern is clearly noticed as the ground surface becomes smoother like a mirror. Although the roughness of the striped pattern is not so large, it becomes the problem that the pattern can be observed visually. In this paper, the formation mechanism of the striped pattern is investigated through a computer simulation and grinding tests. As a result, it becomes clear that the striped pattern appears on the ground surface due to the interaction between the grinding marks generated by the unbalanced wheel. Furthermore, the striped pattern was easily formed after grinding with faster work table reciprocation or lower cross feed speed.
In order to reveal the mechanism of the electrochemical etching process in ultrapure water, first-principles molecular-dynamics simulations of Si(001) surfaces interacting with OH molecules were carried out on the basis of the Kohn-Sham local-density-functional formalism. A plane-wave basis set was used, and the cut-off energy is 327eV(24Ry). A norm-conserving pseudopotential was also used. We adopt the standard molecular-dynamics method for the optimization of the ionic system and the preconditioned conjugate-gradient (CG) method for the quenching procedure of the electronic degrees of freedom. We determined the optimized ionic configurations and electronic distributions for OH chemisorbed Si(001) surfaces and clarify the etching mechanism. It was confirmed that three OH molecules can chemisorb on the Si surface atom but it cannot be etched and four OH molecules cannot chemisorb on. We concluded that the Si surface atom cannot be etched as Si(OH)4 molecule and hydrogen-termination is necessary to etch the Si surface atom.
In this paper, a technique how to evaluate the damping characteristics of structures packed with balls is experimentally discussed by considering a free vibration response to impulsive force. Test structures are square pipes excitedly packed with glass balls, steel balls and sintered alumina balls. In such structures, various damping characteristics appear by changing the ball size. However, it is difficult to evaluate the various damping characteristics of structures packed with balls by means of general evaluation technique, such as half-power method and logarithmic decrement method. Therefore, a general evaluation technique of damping characteristic applicable to a linear or a nonlinear system, and also applicable to a low damping capacity or to a high damping capacity is examined. In this study, it is experimentally confirmed that the evaluation of such damping characteristics is possible by considering the damping time and the damping wave area in free vibration response.
This paper describes a method to obtain the kinematic parameter for the hexapod machine tools by using telescoping ball bar device. This method deals with length error of struts, positional errors of base and platform joints as kinematic parameters. For finding a better set of ball bar measurement conditions, Fourier transformation is applied to explain error trace patterns of the circular test. Although it is difficult to identify all kinematic parameter errors with about fifteen circles of ball bar measurement, the machine's motion error can be decreased to one sixth when this method is applied. However, in this report, the deformations of struts are not taken into consideration.
This paper presents a method of adaptive control of tapping in order to perform high speed, high productivity tapping by using newly developed intelligent machine tools experimentally. Generally the adaptive control is changing of cutting condition like feed rate and cutting speed. For tapping, it is not enough to avoid troubles that control cutting condition as compared with the other machining modes like drilling and milling. Because feed rate is fixed for pitch of tap, and to control cutting speed is not so effective. This method means changing acceleration speed of tapping by means of the value of cutting torque by monitoring cutting force with internal sensor. To use this method, the cutting torque increase is not so sharp at the hole bottom vicinities because of prevention of chip jamming. In order to inspect the productivity and safety of tapping, a new NC system produced. As a result, productivity improved 34 % experimentally as compared with conventional system. So it is able to have high-efficiency machining without tool breakage in tapping.