In assembly modeling, it is necessary to capture the relative positions of components in the assembly. Many such problems concern constraint representation and its manipulation such as constraint reduction. This paper makes theoretically clear the constraint representation and reduction in the assembly model as follows: first, constraints are defined as groups of rigid body transformations based on Lie algebra. Second, constraint reduction procedure is proposed based on Lie algebra. Finally, this approach is applied to the constraint representation and reduction in an assembly model.
Maintenance Prevention (MP) is an important concept for ensuring reliability and maintainability of manufacturing facilities by providing various information collected during actual operations (MP information) to their design phase. However, in many cases, information collected in the shop floor is not detailed and/or accurate enough to make use of it in the design phase. In this paper, we propose an MP information management system which can facilitate an information flow from operation phase to design phase. The system consists of two subsystems: a malfunction data input subsystem and an MP feedback information generation subsystem. In the former subsystem, malfunction data is represented in terms of a combination of deterioration and failure mechanisms, and properties of facility where the malfunction occurs. In the latter subsystem, malfunction cases which are similar with each other are extracted and generalized to induce MP feedback information by means of attribute-oriented induction algorithm.
The study describes a new NC data generation method for 5-axis control machining, using curved interpolation. In conventional linear interpolation, the amount of NC data tends to increase with increasing the geometrical accuracy of workpiece configurations, which often leads to the reduction in feed speed of machine tools, especially for 5-axis control machining, since a huge amount of NC data can not be accepted in time. On the contrary, as the curved interpolation requires only a few parameters to express workpiece configurations, NC data can be transmitted rapidly, compared with the conventional linear interpolation. The curved interpolation was already applied successfully to 3-axis control machining, however not to 5-axis control one. Thus, in the study, 5-dimensional non-uniform B-spline curve is employed to express 5-axis control curved interpolation NC data in terms of NC data reduction, using 5-axis control collision-free NC data. In a 5-dimensional non-uniform B-spline curve, NC data are significantly compressed by appropriately selecting knot vector on the basis of equally divided curvature area method. From the experimental results of 5-axis control machining, it is confirmed that the curved interpolation has the potential of reducing large amount of NC data without deteriorating the surface roughness and shape accuracy of workpieces.
Three-dimensional (3-D) model can be constructed by composing multiple 3-D data obtained by non-contact 3-D measurement equipment. Recent equipment can obtain not only 3-D position data but also red, green and blue color brightness data. This paper describes an automatic method that utilizes the color information for composing the multiple 3-D data. United distance that is sum of 3-D distance and color distance multiplied by weighted coefficients is defined. Also the mean for calculating the closest point that minimizes the united length using triangular area co-ordinate is devised. The method obtains conversion matrix that minimizes average united distance (d) among closest points of two 3-D data by improving the matrix and closest points repeatedly. Also two-step process is applied; first best conversion matrix is derived from the extracted data points; and next all data are moved and the matrix is improved. The results of the experiment show that when the coefficient 0.9 is used for 3-D distance and 0.1 for color distance, two data can be composed in the position where not only shape but also color of the surface is matched. Also processing time can be reduced one sixth of whole data process by extracting from one thirty-second to one sixteenth data points.
A surface topographic measurement system using a microfork has been developed. The microfork used in this study has two PZTs : one is to vibrate the microfork and the other works as a sensor for the vibration. The principle of the measurement is based on an application of the microfork as a gap sensor, which outputs a DC voltage as a function of the distance from the surface during the periodical tapping on the specimen. A height control system together with a piezo-driven XY scanner is constructed using a PI controller with a settling time of 80ms for a step input of 0.1μm. Thus a topographic information is obtained from the height combined with the XY positional information. Some examples of measurement are shown and compared with those contained by conventional measurement systems. Although the stylus damages the surface a little bit, a fine vertical resolution of 5nm has been confirmed in the measurement.
A technology for improving the measurement accuracy for the surfacq roughness of 3-diatat is east metals, using an optical noncontact method is studied in this work. In particular, the technology to maintain a constant evemga output value is because values obtained using the optical method depend significantly on the average output value of detected images.It is clarified theoretically and experimentally that the average output value depends not only on the surface reflectivity and illuminance but also on the ounce roughness and inclination. An image detection sensor with 2 optical filters is developed and the number of digitized signals is increased from 256 levels to 1024 levels using this image detection sensor. This technology, uses software to maintain a constant average output value of detected images without the saturation of the output value.As a result, the linear between the surface roughness and the value obtained using the optical method, and the measurement sccyracy are improved,
This paper proposes a new optical method for measuring roughness of ground surfaces, especially for a pol-ishing robot. In-process measurement. of surface roughness is an important factor in automatic precise polishing. The roughness of such metallic surfaces can be measured exactly by a stylus roughness meter. However, for the reasons of vibration arising during grinding and of a long time necessary for the measurement, the stylus roughness meter is not applicable to in-process measurement. An optical, non-contact measurement is well suited to harsh environment in grinding processes. In this paper, a halogen light source is used and its reflection from the surface to be measured is collected by a CCD camera. The gathered image data are processed by a newly proposed procedure. Based on the Torrance-Sparrow model, this procedure theoretically converts the data of the reflected lightt into surface roughness represented in Rrms (roughness in root mean square). The correlation between the image data and the roughness of the surface is not sensitive to the brightness of the light source as well as the material composing the surface.
In the design of planar link mechanisms, moving links are arranged in parallel offset planes in order to avoid their mutual interferences. Therefore, not only the input moment, the transmitted force and the output moment but also bending and torsional moments in planes containing moving links (motion planes) act on each link. In this paper, the spatial closed loop equations with very small torsional and bending deflections of moving links of the planar offset four-link mechanism are deduced. Equilibrium conditions of torsional and bending moments acting on moving links are expressed in linear equations of their very small deflections and the torsional rigidity about the revolute axis of the driving link. By solving simultaneously the spatial closed loop equations and the equilibrium equations, the equivalent torsional rigidity and very small deflections of moving links are obtained.
It has been reported that the three pairs of antagonistic muscles including the mono- and bi-articular muscles in human limbs showed the perfectly coordinating activity pattern, and contributed to the output force control and force direction control at the wrist or ankle joint. This paper deals with a method of the functional evaluation of effective muscle strengths in the muscle coordinate system based on the functional role of the muscles contributing to the output force distribution. The output force distribution demonstrated a hexagonal shape, and the effective strengths of the functionally individual muscles could be calculated from the characteristics of this hexagonal shape. This will lead a human model into much more reality than the model operating in the conventional joint coordinate system.
This paper deals with a linear drive mechanism for multiple shaft feeding. Though various small linear drive mechanisms have been developed, they are used to feed single shaft. A unit for multiple shaft feeding has been developed by arranging some feeding devices for single shaft. The proposed feeding device consists of clamps, friction devices for each shaft and a driver. Each shaft can be fed forward or backward direction and can be stationary in a cycle. The feeding principle is investigated by using a device for single shaft feeding. Then a device for three shaft feeding is manufactured in trial. The shafts can be driven up to 100 Hz with a constant displacement. The displacement of the shaft is linearly changed over 20 V as the amplitude of the applied voltage to the driver. This mechanism performs similarly to an inchworm mechanism. However, the proposed device needs less number of actuators than the inchworm mechanism because the driver is commonly used for all shafts and the friction device needs no actuator. This mechanism will be applied to a machining unit for the dot-matrix electrical discharge machining.
A new form rolling technique to produce high performance GFRTP (glass fiber reinforced thermo plastic) thread by heating mini die is developed. GFRTP is widely used due to its superior properties, such as high strength, lightweightness, corrosion resistance and electrical insulation. Thus, the high performance GFRTP fastner is desired in various industrial fields. The form rolling is a standard technique for metal threads. It is supposed that the form rolling of GFRTP rods, in which the glass fibers are arranged along the axis of rods, makes possible for fiber to flow into threads during form rolling period, and the cost effective high performance GFRTP bolts would be available. In order to obtain precise thread shape and high strength, it is considered that the material temperature should be higher than the glass transition temperature and ultrasonic heating has been applied in form rolling process. However, sufficient thread shape could not be obtained, because the high temperature of the inner part causes total material deformation and the forming pressure becomes small. To cope with this problem, a new heating mini die is designed to apply local heating and large local form rolling pressure. It is found that the precise thread shape is achieved and the glass fibers flow into threads by the proposed heating mini die.
In this study, the properties and mechanism of Si microprotuberance processing are evaluated with diamond tip scanning using atomic force microscopy (AFM) in the atmosphere. Microprotuberances on the surface approximately 1-nm-high were formed by mechanochemical action. To control the height of the processed microprotuberances, the height dependencies on load, scanning cycles and scanning area were studied. To clarify the mechanism of mechanochemical action, the contact stress was analyzed by the boundary element method. The following results were obtained:(1) A diamond tip with nearly 100 nm radius sliding produced an approximately 1-nm-high microprotuberance on the Si surface. (2) Processed microprotuberance height increased with applied load. Microprotuberance and microsinkage were produced by sequential scanning and a profile similar to a sine curve was formed after four scannings. (3) To clarify the swelling mechanism, surface contact stress was evaluated. Oxidation and hydroxidation were speculated to occur at the rear edge of the sliding contact area at which the elongation stress is the maximum. (4) To produce the three-dimensional microprofile, the processed profile dependence on scanning area was evaluated, and then 3-nm-high micropyramids were formed as an application of this processing.
It has been known that when micro hole machining was carried out by EDM using a straight electrode, the hole diameters became different at the inlet and outlet of the machining. This shape irregulality is caused by wear of the electrode and eroded particles. In this paper, a new method is proposed for diminishing the diameter differences of the micro hole and forming the straight micro hole by EDM using a stepped electrode. Following experimental results were obtained.(1) The micro hole diameters'become different at the inlet and outlet of the machining by using a straight electrode.(2) The difference in the diameters of a micro hole is diminished and the straight micro hole of desired diameter can be machined by using a stepped electrode.
This report describes molecular dynamics simulations of tensile tests of single crystal pure iron. There are a few experimental data of plastic region tensile tests of pure iron. In this simulation, strain range are elastic and plastic region, and to fracture point and temperature conditions are 100K to 1100K.In this report, different three kinds of models of tensile directions (,  and ) are used. They are axis of rotational symmetry of bcc-type crystals. In the simulation results, stress-strain diagrams are important. They are different from polycrystal iron's in macro-scale. The stress-strain diagrams differ from tensile directions and temperatures. In tensile tests of  and  directions, we find second elastic regions after plastic regions. In second elastic regions, crystal structure types are changed from bcc-type. We find two types of structure phase transitions.
It is extremely important to know the conditions of wheel working face for managing grinding processes. Among the conditions, wear flats and their arrangements are critical because they directly have an influence on the integrity of the surface ground. However, conventional methods or apparatuses are not necessarily sufficient for measuring them as their measuring speeds or resolutions are lower than those required in practical grinding. This paper describes a system for managing grinding processes using high-speed visualization of a wheel working face at a 30m/s practical wheel peripheral speed. Images obtained by this system are almost the same quality as ones obtained by a microscope. The spatial resolution of this system is 6μm. The background, or part lower than the active cutting edges, can also be erased with a precision of about 50μm using a masking technique based on the height data of them.
For aspheric plastic lenses, very smooth surface roughness and high profile accuracy are required. However when a plastic lens is machined from plastics by cutting directly, there is a serious problem in that profile accuracy deteriorates by chucking even if the lens is machined precisely on a machine tool. Consequently, a new chucking technique which decreases the deformation has been developed by analyzing the cause. It has been also clarified that the chucking deformation before machining is different from that after machining. By using this technique, an aspheric plastic lens can be machined with high profile accuracy of less than 1μm.
In this study, a combination of countermeasures to prevent the chipping of the edge of cutting tool is investigated which usually occurs when difficult-to-cut materials such as hardened steels are cut by means of a conventional ultrasonic vibration cutting method (UC). The authors consider that the chipping is caused by the collision between the flank of a cutting tool and the machined surface of a workpiece when the tool moves backward thereby contacting with the workpiece. As a first countermeasure the authors propose a new UC device which has more rigidity and stability than the previous one used by the authors, even when subjected to high cutting resistance. As a further countermeasure, in addition to use of the new UC device the authors try to perform a cutting operation in which the vibrational direction of the cutting tool is inclined from a principal cutting direction at an amount of 10 to 30 degrees toward the workpiece. It is found from the result that the chipping of cutting edge can be substantially prevented and a good surface finish is obtained by both continuous and intermittent cutting modes when cutting hardened steels.
This paper describes geometric change of the substrate surface when Al2O3 particles of 0.5μm diameter, which is larger than ions and smaller than the particles used in blasting and soon, were jetted on the copper, steels and glass. As Al2O3 particles were jetted at a jet angle of 0°, vertically on the surface, Al2O3 particles were deposited on the substrate surface except glass substrate. As jet angle increased, ripple spacing perpendicular to the jet direction with spacing about 2-15 u m was generated on each material and that spacing grows larger with the increase in the jet angle. The spacing varies in the material and harder material shows the tendency to become smaller in the spacing. The ripple spacing grows rapidly larger with the increase in the jet angle. At a jet angle of 80°, the trace which appears in the removed surface along the jet direction becomes remarkable. That was applicable to polishing of the fine pipe.