The authors created a flexible assembly center that can be organized to meet the needs of various assembly operations. For this, a precision autonomous robot that does not require a teaching process was developed. The flexible assembly center is composed of multiple table robots, arm robots, and part/tool feeders, and has the following characteristics : (1) Complicated operations can be performed by using the flexible arm and table setup. (2) The positioning accuracy necessary for precision assembly can be maintained through the use of direct drive mechanisms and auto-calibration, without requiring a teaching process. (3) Precise operation can be accomplished autonomously by real-time control with visual and force sensor feedback. This system is particularly effective for production systems involving frequent setup changes.
Experimental modal analysis has beeen widely used method for vibration analysis. Owing to recent development in hardware and software technologies, it enables to do all process of the analysis, such as measurement of frequency response, curve fitting, mode animations, etc. on a micro-computer. This paper describes a new developed vibration analyzing system based on experimental modal analysis on the micro-computer. In this analyzing system, complex exponential method is used to identify poles in curve fitting process. Effect index is determined to use for a guide to select important poles, because the result of the method may contain some noise mode. Analysis of some structures by this system is also described.
This paper describes a system to measure tooth profiles of a gear. In this system, a movable optical probe detects the displacement of each tooth of a rotating gear at the instant determined by a triggering probe. This measurement on a circle is repeated after the movable probe is positioned at every sampling point in the radial direction. Therefore, sampling time of this system hardly depends on the number of the tooth. In a trial measurement for a spur gear with module 2.5, 40 teeth, it took 20 minutes to measure tooth profiles getting 100 sampling points on every tooth. The deviation of results repeated measurement from average was 2 to 3 μm. Radial motion of the axis that the gear is fixed causes this deviation of the result. The measured results by this system show good agreement with those by a contact one, particularly in the area of low spatial frequency.
A 7 d. o. f. crane with three wires is proposed for automatic heavy parts assembly. The crane can control not only desired position but also orientation of a suspended object. The position and orientation control method of the crane is discussed under a static condition. By solving the simultaneous equations given by the geometrical constraints of the wire lengths and force constraints of gravity, the kinematics is calculated. Since the equations are non-linear, Newton Raphson method is used. The kinematic characteristics of the crane is analyzed and the relationship between the desired orientation and the shape of the object is obtained. Redundancy of the crane is used to minimize the maximum value among the three tensions of the wires. The algorithm of the inverse kinematics is proposed and experimental results using a prototype crane prove the verification of the algorithm.
The purpose of the paper is to realize precise measurement of straight motion accuracy over long travel. The reversal method as well as the sequential three-point method is conventional. However, it is difficult to measure motion accuracy over long travel precisely using either method. The paper proposes a new precise measuring method which will be called the improved sequential three-point method. In this method, the principles of the reversal method and the sequential three-point method are introduced. Straight motion accuracy of a slide table was measured over 850mm travel using the improved sequential three-point method. The standard deviations from 12times measurements were 1.0μm in horizontal position and 2.0arc sec in yaw angle.
A method is proposed to recognize the state of cutting based on sensor fusion by applying neural network approach. The state of tool wear, or the initial, the middle and the final stage of coated tool, the onset of chatter vibration and the onset of chip tangling are succesefully recognized in turning of curbon steel. Methods are also proposed to determine better structure of the neural network and to improve the learning procedure. It is proved experimentally that the proposed method is quite reliable and accurate to recognize the state of cutting.
This paper describes an experimental study on the deformation of an aluminum plate fixed by adhesive to a flexible printed circuit (FPC), which is a laminated structure composed of polyimide resin, copper leaf and adhesive. The deformation was measured by holographic interferometry using a compensation method for interferometric fringes. For example, when the thermal expansion coefficient of the aluminum plate differs from the equivalent thermal expansion coefficient of the FPC, the aluminum plate has an out-of-plane deformation. The thermal deformation caused by temperature changes can be eliminated by controlling the volume of copper leaf so that the thermal expansion coefficients are equal. The aluminum plate also has an out-of-plane deformation due to expansion and contraction of the FPC caused by humidity changes. This deformation can be eliminated by covering the polyimide of the FPC against moisture.
Tapered end mills are useful cutter for machining of inclined surface, for example side surface of mold and die. But there are a number of unclarified points regarding to cutting mechanism of tapered end mills. This paper therefore tries to clarify the cutting mechanism of tapered end mills and aims at presenting basic data on tool design and effective method for using the tools. The main results are as follows. (1) The cutting edge shape and cutting process by chip areas are analyzed geometrically for tapered end mills, and calculating method of the chip areas is shown. (2) Cutting patterns are classified into two types and chip areas for various cutting conditions are calculated. (3) The basic behavior of chip areas by tapered end mills are similar to that by square end mills. But chip areas increase by almost constant ratios in the middle part of cutting process by square end mills in case of type I. (4) Incremental rates of the chip areas in the middle part become large with increase of taper angles and decrease of helix angles.
Grinding performance of ceramics was experimentally investigated to obtain high quality ground components like a curved surface with small roughness and small residual stresses. An electrolytic/electro-chemical in-process dressing method was applied to very fine grain-size wheels for finishing mirror-like surface with low grinding force, in contour grinding of a blade-shaped silicon nitride with a machining center. The relation between the grain size and the surface roughness of the ground ceramics was found. High quality surface of silicon nitride with a roughness of 0.012 μmRa could be accomplished by using a 10 000-mesh metal-bonded diamond wheel. The X-ray diffraction measurement showed that the surface compressive residual stresses increased with increasing feed rate or with decreasing wheel speed. It was found, however, that there was no effect from the normal grinding force during grinding. It then concluded that the residual stresses decreased with decreasing chip cross sectional area.
The perpendicular guideway mechanism is required high coupling characteristics and high. precise slide motion of the slider. In this paper, the coupling characteristics (static and dynamic) of the grinding wheel head (slider) are considered by using perpendicular guideway of an actual surface grinding machine. In conventional type guideway, the slider to slide along the guideway, the gap must be provided between two opposite sliding surface. When the gap is wide, the slider performs undesirable motion in addition to the slide motion. Conversely, this gap is narrow, the sliding friction increases in the slideway. However, appropriate friction is achieved damping effect as the dynamic coupling stiffness. For these reasons, it is proposed that new type guideway satisfies the requirement. The new type is called composite bearing guideway mechanism (one side is slideway bearing and other side is hydrostatic bearing guide way). As the result, this paper is obtained to achieve high coupling characteristics from experi mental and analytical results.
It is known that a groove can be shaped toward a wafer orientation (depth direction) by anisotropic etching with a mask arranged to a certain crystal direction and the accuracy of finished profiles is damaged because of an effect of side etching (unexpected etching toward side direction). The present paper has analyzed this side etching process by the help of reaction cage effect theory in the previous paper and can quantitatively estimate both the rate of side etching and the accuracy of finished profiles.
A finite element modelling is proposed for simulating the discontinuous chip formation of 60% Cu-40% Zn brass. In the modelling geometrical nonlinearity and the reduction of constraint of incompressibility in the large deformation of finite elements are taken into account. The initiation and growth of ductile cracks from cutting edge to chip free surface during chip segmentation are directly introduced into the finite element model using an appropriate fracture criterion, which is determined in terms of strain, strain rate and hydro-static pressure. Chip segments, which are periodically formed in the simulation, are in good agreement with those experimentally obtained both in configuration and deformed grid. Variation of velocity, stress, strain, strain rate calculated during a chip segmentation make clear the mechanism of discontinuous chip formation. Normal and frictional stresses on the rake face calculated are found to be almost uniform over the tool-chip contact length.
The purpose of this study is to obtain the optimum conditions for forming the high precision machined surface by diamond cutting. Therefore, the affections toward the formation of surface by the variation of the tool damage and the whisker orientation were clarified. The results obtained from this study are as follows : The states of tool damage of single crystal and sintered diamond tool and carbide tool had the abrasive type wear, and the tool wear was expressed as the degradation of surface. The most suitable tool for forming the precision surface was the sintered diamond tool with middle size of diamond grain because of the favourable effect of the falling-off of diamond grains. 0.2μm of surface roughness and 0.5μm of surface contour were obtained. And, by setting the whisker orientation parallel to machinedsurface, the whisker was easily fell off and the surface was degraded.
Repairing of minute cracks on a surface of the advanced ceramics is one of the important technology for practical use, since the cracks decrease the flexural strength. This paper describes the repairing method for sintered silicon-nitride based on heating with pulsed YAG laser irradiation. Laser heating for 20 seconds in atmosphere of nitrogen gas increases surface temperature to 1600-1750°C. A controlled surface flaw introduced with Vickers indentation, depth of which is 100 μm, disappeared after the laser heating, and the flexural strength at room and elevated temperatures became the value of a specimen without surface flaw. This method is applicable for repairing cracks on the ground surface with diamond grinding wheels. The repairing with laser irradiation is thought to be caused by resintering with the sintering aids and by boundary consolidation with crystallization siliconnitride-yittrium-oxide.