A method of improving particle size measurement accuracy has been developed by the correction of detected signals in dark-field particle detection technique. By this dark-field size measurement method, real-time particle size distribution measurement can be realized. A method of yield impact evaluation has been developed in which non-killer small particles are to be eliminated from all detected particles such that the yield impact is maximized. Extracting only killer particles from enormous amount of particles detected by high sensitivity particle inspection can be realized by this yield impact evaluation method. These methods are confirmed to be useful for a dark-field particle inspection on multi-layer films as a result of some experiments.
In this paper, the error in the measurement of a gap larger than 0.3mm inside a quadrilateral hole, using an optical noncontact measuring equipment, is discussed theoretically. The experimental results show that the measurement error of the gap varies with the gap length of the specimen. It is verified in this paper that the cause can be analyzed by taking into account the spherical aberrations of the lenses in the measuring equipment. The maximum spherical aberration of the lenses was 50μm. The maximum measurement error of the gap is denoted by e. The calculated results show that e is +1.0μm in a 0.3mm×0.3mm square hole, e is -0.30-0.35μm in a quadrilateral hole with a gap larger than 0.6mm when the spherical aberration is taken account and e is always negative when the spherical aberration is assumed to be 0.
More than 80% of the pattern defects in a semiconductor manufacturing process are caused by the adhesion of particles on a wafer. In a production line, the particles larger than 0.2μm in diameter on the wafer on which a SiO 2 thin film had been deposited, have to be detected. In this study, the intensity of light scattered by particles 0.2μm in diameter on the wafer on which a SiO 2 thin film had been deposited, without being influenced by the thickness variation of the thin films, is detected using an experimental apparatus. The following results were obtained. (1) P-polarized laser light with the incident angle of 75° is suitable for the illumination. (2) A method of detecting the light scattered perpendicularly upward from the wafer is suitable. (3) The variation of the detected light intensity is 57% when the light scattered by a particle 0.2μm in diameter on a wafer on which a 0-300-nm-thick Si0 2 thin film had been deposited, is detected. P-polarized laser light is suitable because the variation of the detected light intensity when a particle is illuminated by S-polarized laser light is 96%. The above-mentioned experimental results coincide fairly well with the results obtained by simulation.
The piezoelectric elemnet has high positioning resolution although it suffers from the problem of a rather small displacement range. The proposed actuator can achieve both a high positioning resolution and a long stroke. This mechanism is modified the construction of Impact Drive Mechanism(IDM), and is named Smooth Impact Drive Mechanism(SIDM) because of the smooth movement. To drive SIDM, the piezoelectric element is expanded slowly, and is contracted rapidly. The waveform of displacement of piezoelectric element is as saw-tooth. To generate saw-tooth displacement, saw-tooth voltage has been supplied. But the saw-tooth voltage is not always best, because transfer function from voltage to displacement in the piezoelectric element is not flat. It is necessary that the transfer function is considered to optimize waveform of voltage. By simulation it is found that the optimum waveform at 0.7 scale of resonance frequency is similar to rectangular pulse. And it is reported that SIDM can be driven by using the rectangular voltage.
The authors have developed a gauge block measurement system where three frequency-stabilized lasers are used as light sources. The stabilized lasers are as follows: I 2-stabilized offset locked He-Ne laser (633 nm), I 2-stabilized Nd:YAG laser (532 nm), and Rb-stabilized diode laser (780 nm). b-stabilized offset locked He-Ne laser is commercially available (Nihonkagaku Engineering CO., LTD.) and its relative uncertainty of the wavelength is 2.5%times;10 -11 I2-stabilized Nd:YAG laser and Rb-stabilized diode laser were developed in our institute and their relative uncertainties of the wavelength are 5×10-12 and 1×109, respectively. In the measurement system, laser lights were introduced to the interferometer using an optical multi-mode fiber. An interferometric fringe pattem was taken using a CCD camera and the excess fraction parts were calculated from the fringe pattern using the Fourier transform method. This interferometer can measure gauge blocks of up to 1000 mm long and the uncertainty of the interferometeris about 75 nm in 1000 mm gauge block.
In this paper, non-linear characteristics of a piezoelectric actuator such as hysteresis and creep are investigated experimentally. When the actuator. is driven by sinusoidal inputs with different amplitude, upward curves in hysteresis loops of displacement versus input voltage are on the same curve if they are drawn so as to coincide their minimum point in a graph. The curve can be approximated with a polynomial function. Also creep behavior can be reduced by step drive with appropriate overshoot. On the basis of the preceding facts, a new open loop driving method for stack type piezoelectric actuator is proposed for stepwise positioning. In the method, the driving voltage is dropped to 0V and set to a constant value called initial standard voltage before every stepwise drive, and then forwarded to required step height with some overshoot. Influence of both of the hysteresis and creep characteristics are eliminated by the method drastically. Precise stepwise positioning with constant step height is realized under open-loop drive.
Drill breakage is one of the major problems in micro drilling and in-situ breakage prediction can improve production reliability remarkably. The authors have already reported an in-process detection of small cutting torque by the new torque sensor with a thin-walled elastic cylinder. In this paper, a feed control drilling according to an overload signal from this torque sensor is described. In order to prevent the drill breakage caused by the overrun of a drill feed stage, it is necessary to stop the drill feed quickly enough according to the overload signal. A quick stop mechanism, which consists of z stage for the drill feed motion by regular NC control and z' stage for a quick retreat motion, was developed. The advancing z stage can not be stopped quickly due to electric delays of feed control and the mechanical inertia. The quick retreat motion of z' stage according to overload signal can cancel this time delay of z stage. The automatic canceling motion can prevent drill breakage during the drilling operation. Through a few drilling experiments of multi-layered printed circuit boards, the availability of the developed quick stop mechanism in automatic feed control was verified.
The conventional method for aspheric surface diamond turning is the arc-enveloping method. In the present study, a new method termed the straight-line enveloping method is proposed, in which the aspheric surface is generated using a straight-nosed diamond tool on a three-axis simultaneous control ultraprecision machine tool. This method is preferable to the conventional method for the machining of convex aspheric surfaces on hard brittle materials since it significantly improves efficiency and lowers tool wear. The experimental setup configuration and the tool setting method are described and the formation of form error is analyzed. An aspheric lens having 1.36μm form error and 78nmR ysurface roughness was obtained on a 120mm diameter single-crystal silicon substrate at a tool feed rate of 20μm/rev. by applying the proposed method.
Oil-submerged cuttings were conducted on an NC precision cutting apparatus in order to measure the influence of the lubricant applying effect on lubrication. The tool and work were completely submerged into cutting fluids which contained in an oil bath. Any deviation in lubrication due to oil supplying method, operators, and etc. can be eliminated by this method. The cutting forces in the oil-submerged cutting were compared to those in the lubricant applying effect cutting. The comparison indicates that the lubricant applying effect shares a high percentage in the lubrication. In other words, it plays a major role in lubrication in most cutting conditions, which enables semidry machining.
In this paper, spherical surface molding of polymer using a liquid mold system is described. A liquid droplet has spherical surfaces at the liquid-liquid interface due to interfacial tension. The curvature of the spherical surface is determined by the degree of interfacial tension applied at each interface. Interfacial tension between some liquids was measured, and the shape of a photopolymer droplet between the liquids was calculated. Ultraviolet light was irradiated onto a photopolymer droplet located at the liquid-liquid interface, using a superhigh-pressure mercury lamp. Photopolymer droplets solidified and lens-shaped objects were produced. Cross sections of these objects were observed, and the curvatures of the spherical sufaces were found to correlate with the interfacial tension. A spherical solid was formed at a water/salt solution interface. The possibility of forming various spherical surfaces by exploiting liquid-liquid interfaces was revealed.
The wear mechanism of a binder-less cBN tool on the high speed turning of the gray cast iron was investigated. The tool material was characterized to have excellent both mechanical and thermal properties, owing to microstructure consisting of single phase cBN with extremely fine grain, resulting in confined flank wear in the initial stage of turning at condition of V=33.33m/s. The confined flank wear extended the tool life as long as 16 times compared to that of the conventional type of cBN tool. According to the precise observation of the tool surface in the course of the turning operation, an A1 2O 3 based adhered layer from workpiece was build-up on the tool flank face. The adhered layer became to exert as a protective film which prevented direct contact between tool and workpiece, resulting in a significant decrease in tool flank wear. In the turning of the workpiece material with lower Al content, the tool life was shortened because of lower possibility of formation of the adhered layer. The tool life was also shortened at the turning speed higher than V=40.00m/s. X-ray diffractometry and scanning electron microscopy of the adhered layer formed in the higher speed conditions, clarified that the layer consisted of a spinel type MgAl 2O 4 crystal which has inferior mechanical properties compared to A1 2O 3
In this study, influence of fitness of the taper connection of the spindle on the natural frequency on bending vibration of a test bar was studied. The spindle taper must sustain not only a large thrust force but also a large radial force due to the cutting forces, and the large radial force makes front end of the taper expansion gradually in the long term. The expansion of the spindle taper brings the deterioration of cutting ability of the machine tool, therefore the users must regrind the expanded spindle taper when the expansion exceeds a permissible amount. However, this amount is determined empirically in general, because the relation between expansion of the taper and cutting performance has not been clarified yet, and the extent of the relation changes with the change of the static and dynamic behavior of the machine tool. In this study, therefore, the natural frequency of a test bar was used to estimate the spindle taper fitness. Furthermore, end milling chucks having different taper length were also used in cutting tests. As a result, the frequency was strongly influenced by the fitness and the taper having 85% fitness in length by expansion must be reground, because cutting performance of such taper is extremely low compare to that of 100% fitness taper.
Institute of Mechanical Systems Engineering, AIST, Japan proposed a concept of a microfactory which consists of tiny machine tools and robots. In terms of energy efficiency, a large machine represents considerable waste. Miniaturization of machine tools to size compatible to the target products without compromising machining tolerance leads to enormous savings in energy and space. In 1996, an ultra miniature lathe only 1 cubic inch large was developed. The success of the lathe was the driving force to prototype a factory that performs several processes on a desktop. For the machine tools of the microfactory, the existing experience of machine tool design may not be applicable. Machine tool designers will need a general design guideline to appropriately reduce the size of machine tools. The latter half of this study combines an analytical procedure representing the machining motions known as form-shaping theory with a robust design procedure. The effort identifies the effect that the machine tool structure has on its machining performance. From two design candidates of the miniature milling machines, the method can tell which design has a better theoretical performance. The result leads us to conclude that the design evaluation method is applicable to conceptual design of machine tools.
This paper deals with the method of tool path generation on CAM system for 5-axis machining using a concept of haptic virtual reality. 5-axis machining has been used for complicated shapes such as turbine blades, molds and dies due to the efficient and accurate machining. However, present CAM systems for 5-axis machining lacks in generality and functions for the tool path generation. Especially, the interference between a tool and surrounding objects in computing the tool path is still a big problem. The method of tool path generation devised in this study uses operator's assistance. In this CAM system, first of all, the operator inputs information of suitable tool posture for all polygons constructing object shape. After that, the CAM system can compute a tool path without repetitive algorithms because tool posture avoids interference have been already input the system. Using a haptic device and a newly developed rapid interference detection algorithm, it is possible to touch the surface of the object, and easily input information of suitable tool posture into the CAM system. From the experimental results, the validity of the method is confirmed.
This paper investigates the availability of aerostatic journal bearings to a high vacuum chamber, theoretically and experimentally. This bearing has several steps of a viscous seal, and vacuum pumps are connected to the space between viscous seals in order to achieve the vacuum degree of less than 10-3 Pa in a vacuum chamber. The vacuum degree of a chamber is affected by many design parameters such as the number of steps of a viscous seal, seal length, seal gap, the pumping speed of vacuum pumps and the conductance of exhaust tubes. Influences of these design parameters on the vacuum degree are theoretically discussed and the theoretical predictions are compared with the experimental data. It is found that the aero-static journal bearing with viscous seals can achieve the vacuum degree of the order of 10-4 Pa in a vacuum chamber by properly designing the seal regions.
The method which generates bending process plan for sheet metal bending with handling robot is proposed. In process planning for sheet metal bending with handling robot, grasping position and reposition timing must be determined as well as bending sequence, tools and gage position for measuring bending line. Bending operation is always accompanied with errors such as spring back, gage positioning error. In addition, these errors are accumulated to some specified dimension so that process plan in which the errors may not be accumulated on critical dimension must be decided. In this paper, the problem of accumulated error is solved by using graph and tree. The graph which consists of bending line and faces is generated by flat pattern and the tree which is specified by grasping position of handling robot as root node is generated by the graph. And then, some heuristic rules for solving the accumulated errors are presented. As a result, bending process plan can be obtained by applying these heuristic rules to the tree. Computer simulation was carried out based on the proposed method. Illustrative examples and results of simulation are given. The effectiveness of this method is discussed.
This paper presents a new method for kinematic synthesis of mechanisms from motion task specifications in a conceptual design. The motion task is classified into continuous path or positioning task. The former is the task that moves a mechanical part along a required path, and the latter is the task that puts the part in a particular position or orientation. The authors formulate them mathematically using Lie algebra and propose a method for generating an initial solution of the mechanism that can perform the specified motion tasks. From this solution, the constraint reduction procedure can reduce the redundant constraints such as joints to derive a minimum equivalent mechanism. By applying this mechanism to the synthesis procedure proposed in our previous report, a number of equivalent mechanisms can be derived. Finally, in order to evaluate the usefulness of the proposed method, it is applied to an example of kinematic design of mechanism.