This paper proposes a design methodology for self-maintenance machines that can maintain their functions for a while, even though faults happen. In order to achieve the capabilities for diagnosing and repair planning, a model based approach that employs qualitative physics is proposed. Regarding the repair executing capability, two types of repair strategies are proposed; viz., control type and functional redundancy type which is a strategy to add redundancy to a machine from a viewpoint of function. This paper also reports the development of a control-type self-maintenance machine that can maintain its functions as far as its structure does not change.
This paper presents an analytical method for the production rate of flexible lines which are used in many cases recently. The method is based upon the analysis for fixed lines which has been presented. Flexibilities in this paper are as follows : (1) Several kinds of jobs are machined and assembled in each, (2) each lot of jobs is handled at random, (3) the lot of jobs is handled in turns. In each cases, preparing time at changes of jobs and the stoppage time by troubles or interferences of stations is considered statistically. The production rate of lines is given by sum of those stoppage time. Results by the method are compared with results of simulations and both results show a good agreement.
Abrasive grains are generally crushed in a lapping process, resulting in the change of grain size and its distribution with lapping time. In this paper, a method is proposed to simulate the time-dependent distribution of the size of abrasive grains in lapping. The simulated results are compared with experimentally obtained results. The main results are as follows ; (1) The distribution of the abrasive grain size is successively expressed by the equation (7) in the text. (2) The distribution is mainly determined by the following three parameters, a fracture onset probability P, a multiplication rate r and a transition probability q. (3) The simulated distributions are almost the same as experimentally obtained ones. Therefore, it can be concluded that the method for the simulation is correct in principle. (4) For more precise simulation, more adequate values of the fracture onset probability must be used, which can be obtained from the measurement of the mean size of abrasive grains.
A pinhole method is applied to evaluate power density distribution of laser beam converted by a kaleidoscope for CO2 laser processing. An experimental method is developed to measure the power density distribution of the laser beam with use of a pinhole and a thermocouple. Theoretical analyses are carried out to evaluate the power density of the laser beam through the pinhole at the point of the thermocouple. A form error coefficient is proposed to compensate the loss of power when the laser beam is reflected in the kaleidoscope. The theoretical distribution of the power density is in good agreement with the one obtained by the experiments. It is concluded, through both the theoretical analysis and the experiments, that the pinhole method is effective to evaluate the power density distribution of the laser beam converted by the kaleidoscope.
A single-crystal diamond has a large anisotropy in lapping stock removal depending on its crystallographic orientation. Moreover, the rough diamonds have the individual difference of lapping difficulty each other, even on the same plane and direction. Therefore, the wear performance of diamond tools are effected by its crystallographic orientation and its wear characteristic of the rough diamond used as tool material. Eliminating the difference of individual substance of rough diamond, only one rough diamond was sawed into four, and the four kinds of diamond tools in crystallographic orientation were lapped up. The effects of diamond anisotropy on tool wear were examined. By electron probe surface roughness analyzer (SEM with 2 or 4 detectors), the topographs and contours of worn tool edges were obtained. The contour lines of worn tool edges were discussed by the crystallographic orientation route of tool edge from face to flank. The crystallographic orientation route of tool edges were capable of representation as diagram of developing chart of diamond reference sphere on the restricted Mercator's projection. From the diagram of the tools, the evidences had been given that the wear shape of tools corresponded with the lapping difficulty on crystallographic orientation of the routes respectively.
The chaotic behaviour of surface profile produced by turning is investigated in this paper. A new method based on the chaotic theory for characterizing the machined surface texture is proposed. It is recognized by calculating the Lyapunov exponents of the attractor in 3-dimensional phase space and its correlation dimension whether the surface profile has the chaotic characteristic or not. All of the surface profiles produced by turning under the different machining conditions in experiments show the chaotic characteristic. It is also found that the strange attractors, the correlation dimensions and the Lyapunov exponents of the surface profiles produced by turning have relation with the machining conditions and the measurement conditions of the profiles.
Zirconia is regarded as the structural materials of machine element which provide the distinct properties of tenacity by the martensitic transformation from a tetragonal phase to the monoclinic or rhombohedral phases under the plastic deformation and the brittle fracture. The present paper makes clear the relationships between both fracture modes and the phase transformations. In several machining processes which form the surface with both fracture modes, it is experimentally examined how the surface roughness and the phase transformation influence to the toughening of ZrO2-Y2O3. The phase transformation plays an important role in grinding and shotpeening, but the surface roughness influences much to the toughening of ZrO2-Y2O3 in oscillated wet-lapping. In grinding, a tetragonal phase equivalently transforms to the monoclinic and rhombohedral phases, but a monoclinic phase is mostly presented in oscillated wet-lapping and shotpeening. It was made clear that the plastic deformation related to the transformation of tetragonal phase to a rhombohedral phase, as well as the brittle fracture related to the transformation of tetragonal phase to a monoclinic phase.
With the objective of producing a ceramic tool for hardened steel cutting that is 10% the price of cBN sintered tool but with equal cutting performance, a TiN-Al2O3 ceramic tool was developed in which Al2O3 particles are dispersed throughout a matrix that uses TiN as the principal component. When bearing steel (SUJ2, HRC60) is cut, a TiN-Al2O3 ceramic tool that is 40vol% Al2O3 particles produces 25% less flank wear than does a cBN sintered tool. Furthermore, by the time the flank wear land width VB reaches 0.2mm, the surface roughness of the cBN sintered tool worsens to 4.0 μmRmax; however, that of the TiN-Al2O3 ceramic tool is maintained at a value better than 2.5 μmRmax. Also, investigation of the residual stress in the machined work found no difference between the TiN-Al2O3 ceramic tool and cBN sintered tool, Even if a cBN sintered tool were to be substituted with a TiN-Al2O3 ceramic tool, no problem would generate in the residual stress of cutting surface.
Bonding test of thin grinding wheels has been performed, using bit type testing machine. Bit displacement and torque were inversely proportional to the bonding grade of wheels, and were more closely connected with the bond contents. The torque needed to pulling out a grain was obtained as a function of the amount of bond contents per one grain. It was found that, the higher the bonding grade wheel, grains were more breakable than the lower one.
This paper deals with the temperature and thermal deformation performance of the machine tool spindle with high speed and under-race lubrication. As a result of measurement on rotating test, under-race jet lubrication has succeeded in rotating at a 20000 min-1 (dmn=2.5×106) and achieved a high precision on a small thermal deformation by oil cooling of the spindle inside, and also achieved a smaller power loss than usual oil-jet lubrication, because the amount of lubricant used was much less than that of usual oil-jet lubrication system to get the same speed. In the same way under-race oil-air lubrication achieved a higher rotational speed than usual oil-air lubrication, and also achieved a further high rotational speed by using ceramic ball bearings. Analysis of preload increment showed that oil cooling of the spindle inside is better than the use of ceramic ball bearings in terms of preload restraining effect.
In previous report [J. Japan Soc. Prec. Eng., 59, 3, (1993) 491.] under considering wheel surface topography and ground surface profile, it is theoretically predicted that a spring constant of grain mounting is extremely small in a very top surface of grinding wheel, and that the average of the spring constant and its variation become higher in the inner position from the wheel surface. In this report in order to make clear the displacement behaviors of abrasive grains during grinding process, the spring constant of individual abrasive grain mounting on the vitrified wheel surface are experimentally determined from the load-displacement curve of an abrasive grain measured by micro-Vickers hardness tester. The distribution of spring constant of abrasive grain is first analyzed and then it is made clear that the spring constant mentioned above can be predicted theoretically. And it is also made clear that the spring constant becomes to increase or decrease by steps as the elastic deformation or breakage takes place in the bond material.
A mobile robot named TO-ROVER III which can go up and down stairs has been developed. The driving unit mechanism is constructed by a star-like arm, 6 wheels attached at each arm tip, and planetary gears through which a motor drives the arm or wheels. TO-ROVER III has two driving units and a caster with similar mechanism of no planetary gears and no motor. The features of TO-ROVER III are (1) it has only two degrees of freedom, the same as an ordinary wheel type mobile robot, (2) the mode of running on the flat ground and the mode of going up and down stairs are automatically changed, (3) any control is not necessary for a mode change and stair climbing, (4) it can also go up and down helicoidal stairs, (5) motor torque and force for climbing up stairs is smaller than the ordinary wheel type mobile robot, (6) stair climbing motion is quite stable. Kinematics and dynamics of TO-ROVER III have been analyzed, and the experiments show smooth motion in running, turning and climbing up and down stairs.
This paper deals with a method of correcting mechanical crrors of robots. Concerning the correction of mechanical errors of robots for actual production lines, we developed a method that achieves the desired results easily without any measuring devices. The influence factors of geometric and non-geometric robot parameters on the precision of position repeatability is analyzed for the correction of mechanical crrors. For geometric parameters, processing and assembly errors of the component parts and deformation of the links caused by the variation of temperature, A simulation model is proposed to identify these parameters. For non-geometric parameters, gear backlash and the deformation of links caused by loads, the model for the modulus of elasticity and backlash of individual linkages is analyzed. The experiment indicated that all the mechanical errors addressed in the study were treated as geometric parameters. Finally, we propose a model that treats the mechanical errors uniformly based on the experiment results.
A non-contact technique to detect a narrow crack on a ceramic plate has been developed. When a laser spot with the diameter of about 15 μm is illuminated on a ceramic plate, the laser is diffused within the ceramics and interrupted by the crack. The crack is detected automatically by detecting the difference of irradiants on each side of the crack. A TV-camera is used to detect the distribution of irradiant on the ceramics. Windows set on TV-image integrate output signals, and the difference of signals at two windows is obtained. The optimum position and size are discussed. Some cracks are tested using the experimental apparatus. Experimental results show that this crack detection technique detects the cracks of 0.5 μm at an S/N ratio of 2.
The automatic inspection system for TAB (Tape Automated Bonding) -type lead defects has been developed using image processing technique. In this system, the pattern matching method is used for inspection of defects. The positioning accuracy within the image of 1 pixel (about 5.2μm) is required for this method. Therefore the X-Y-θ stage with flexure hinges driven by piezoelectric actuator is designed for improving the positioning accuracy. The inspection method by using this developed system is shown below. The TAB lead is fixed by solenoids on the stage. The stage is controlled by a personal computer which is connected with the CCD camera. After detecting the position of the lead by image from CCD camera, the stage is moved to optimal position. Then the lead is inspected by the image processing computer. The obtained conclusions are as follows : (1) The positioning accuracy within 1 pixel is obtained. (2) The lead defects of about 10 μm (2 pixels) can be detected with the cycle time of 5 seconds.
In assembly works, robot has to control the combined force acting between two bodies. When robot is driven by coarse steps, as much as 0.1 mm and 0.1° step, it is very hard to control the magnitude and position of the combined force. This report proposes to insert an elastic body between the handling body and the robotic force sensor, analyzes the controllability of the synthesized force, and assures experimentally the analytical results. Conventionally, the position of the combined force is controlled by the rotational drive. This report clears that the elastic body insertion makes it possible to control the force position by the prismatic drive in addition to the rotational drive.