This paper presents a method for analyzing the complete behavior of robotic manipulators with flexible links, in order to simulate motion of robot at the design stage, The strict dynamic properties of robot can be obtained by using Lagrange's equation of motion and finite element method (FEM) and program, including modeling of complicated structure of joints and control system. This method is added to the simulation system of robot motion (TOMCAT) which has been previously developed here. The method presented here provides a useful analytical tool to design lightweight, highspeed robots.
This study deals with the automatic determination of part specifications from assembly drawings, such as the assembly sequence and the distribution of tolerances. This paper describes a new algorithm for generating assembly/disassembly sequence of functional machine unit. The algorithm is based on a data model of assembly structure described by connective relations among parts. The algorithm for generating disassembly sequence can be divided into three stages. In the first stage, a set of parts are listed as candidates to be disassembled. In the second stage, one part is selected from the set according to the rules arranged in the order of the ease of disassembly. In the third stage, the selected part is actually disassembled using an appropriate procedure. These three stages are executed recursively until all parts are disassembled. This paper also discusses an optimal disassembly sequence to minimize the number of the changes of direction in disassembly and the number of tools changes. This algorithm is implemented as a rule based system in Prolog. Through the experiments on the machine units, including a headstock of eighty parts. The solutions are the same to those determined manually by skilled engineers.
For the purpose of improving the productivity of manufacturing metal molds and dies, an operational prototype of a real time numerical control system has been developed. It accepts the geometrical data of the parts to be machined, and thereon generates the NC commands in real time during the machining process. The software architecture is first introduced which has been designed to materialize the characteristic capabilities of the system. The algorithm is described that has been developed for the high speed calculation of the intersections among multiple surfaces given as the geometrical input data and the detection of the three dimensional interference of the cutting tool. The simulation results of tool interference demonstrate the possibility of the high rate calculation that is necessary for the real time mode generation of the NC command.
The basic dynamic load rating of ball screws has always been calculated by an empirical formula for angular contact ball bearings. The application of the formula to ball screws, however, causes several contradictions with the characteristics of the fatigue failure which are obtained from the life tests in the previous reports. In the present report the life formula of ball screw is derived by an introducing the ball slips on the raceways, the variation of nut stroke and the state of load distribution in ball screws into the Lundberg and Palmgren's theory. Some compatibility between the life theory and the results of life tests are also discussed. The main results are as follows: (1) The surface shearing stresses which are increased by the slips between balls and raceways can be taken as a basis for an estimation of the fatigue strength of ball screws. (2) The differences between the fatigue strength of shaft and nut become clear through the considerations of number of stress cycles and length of stressed raceway which correspond to a variation of the nut stroke. (3) The theoretical explanation of the growth of initial fatigue failure at the nut raceway on the back side of ball return tube is given by the analysis of load distribution in ball screws and the introduction of their equivalent load into the equation of the basic dynamic load rating.
A ball screw and a planetary roller screw, which accommodate rolling elements between the screw shaft and the nut, have high efficiency. It is generally said that the planetary roller screw has advantages over the ball screw about static stiffness and vibration. It is the purpose of this study to compare static stiffness and vibration of the planetary roller screw with those of the ball screw of the same size experimentally. As a result, it is clarified that the static stiffness of the planetary roller screw is 50% larger than that of the ball screw and that the vibration of the planetary roller screw is larger than that of the ball screw because the planetary roller screw has gear system.
This paper describes the development of a new type of autobalancer for grinding wheels. It is based upon the principle of centrifugal force method. This equipment consists of an instrument for measuring unbalance and a mechanism for moving two balance weights, which are placed in the wheel flange, while the wheel is rotating with its own spindle. The outlines and the characteristics of the developed autobalancer are as follows: (1) The unbalance of the grinding wheel spindle system is measured using a vibration pickup mounted on the wheel spindle head and a synchroscope while the spindle is rotating at normal operating speed. The magnitude and the phase of the unbalance can be found by the amplitude of the wave displayed on the synchroscope and by the synchronizing signal respectively. (2) Two ring-shaped balance weights are automatically shifted in X and Y directions through two sets of a stepping motor and a feed mechanism while the spindle is rotating until the predermined balancing accuracy is achieved. (3) The performance tests show that the developed equipment is superior to the conventional type of balancer (gravity method) in balancing accuracy and speed, and can be put for practical use.
A new twin-pulsed high-speed holography system which can record two frames continuously, was developed for the recording of high-speed phenomena with high temporal resolution. Two phenomena which occur at different time are recorded in one hologram, and after photographic processing, the images of the phenomena can be reconstructed independently. Using this system, diesel fuel injected into the open atmosphere was recorded, and spark ignition of fuel gas was also recorded by double-exposure holographic interferometric method.
The influence of servo control components has been studied to the motion error of NC machine tools by using double ball bar test. The motion errors generated by servo components error, were theoretically analyzed. The DBB measurements were conducted with using many NC machine tools to obtain error motion while they were driven at different feed rates and different time constants. These measured error motions were compared with those obtained theoretically. The results show that out-of-roundness error, radius decreasing error, step and peak error at the quadrant change, and higher harmonic component's error were intimately related with the servo control components errors.
This paper describes influence of a land ratio and a number of land on the grinding characteristic of segmental wheels in creep feed grinding experimentally and theoretically. It has been proved that segmental wheels have the effect of reductions in grinding force, grinding temperature and wheel wear. However, these merits of segmental wheels are not available without both the optimum land ratio and the optimum number of lands which are appropriate to a given grinding condition. Practically, these optimum conditions are determined by the method of trial and error. As a result of experiments and theoretical analyses of cutting force and wear, the followings became evident. (1) The optimum condition exists in combinations of the land ratio and the number of lands. At this condition, grinding force and wheel wear are reduced to a minimum. (2) Cutting force per one cutting edge has a maximum at a front part of a land, and is reduced at rearward part of the land. Therefore, the wear behavior of cutting edge on the land varies with its position. (3) The optimum condition of the land ratio and the number of lands can be determined according to the theoretical analyses.
This paper presents several cutting models for three dimensional cutting with abrasive grains of two triangular rake faces of plus inclination. The models are designed for continuous chip formation along or across the edge line, incomplete chip formation, wall formation of partial chip or plastic upheaval along the groove cut and separate chip formation by each rake faces. Their deformation may be interpreted as a piling of plane plastic flow. An energy method is developed for the proposed cutting models, which enables to predict the formation and the component of cutting force by using the data in orthogonal cutting under equivalent cutting conditions. Then the cutting force components FH and FV are measured and further the transition state between the models are observed by changing the inclination of the 2nd triangular rake face made of sintered carbide in turning experiment. The measured results are in good agreement with the analytical results except for the normal force FV in the case of model [II, IV] and [VI].
This paper describes the side burr produced on both sides of cut surface in orthogonal cutting. In the theoretical study, side burr-root thickness k, corresponding to maximum depth of yield bound, is numerically calculated based on a plane stress model under uniformly stressed on a shear zone by the resultant cutting force. In the experimental investigation, the k is measured in some cutting conditions and then appropriateness of the theory is verified. Furthermore effects of cutting conditions on the k is evaluated both theoretically and experimentally. Main results obtained are as follows: (1) The increase of depth of cut and cutting edge radius enlarge the k. (2) The increase of rake angle and cutting force diminish the k. (3) The decrease of shear stress on a shear plane and friction angle on a rake face and the increase of tensile yield stress diminish the k. These results obtained by experiments represent a good agreement with theoretical results quantitatively.
A cutting model taking account of the variation of working normal rake angle, cutting velocity and others along the chisel edge is developed for the case that the chisel edge portion is thinned to be a uniform tool-chip contact length. It is assumed that the deformation in a plane containing the cutting and the chip flow velocities takes place as in two-dimensional plastic flow. The mode of deformation consists of three straight lines of velocity discontinuity. The model including seven variables with respect to the geometry of deformation zone and velocities represents that the whole chip produced by the chisel edge is to be a helical one, although the cutting and the chip flow velocities vary in magnitude and direction at each point on the chisel edge. Applying the energy method to the model equations are derived for the prediction of chip formation, torque and thrust.
The cutting temperature in the ultra-high precision diamond fly cutting of copper is discussed based on the experimental data. The cutting temperature and the temperature rise in the workpiece are measured with the thermocouple of copper and constantan wire. The temperature distributions in the workpiece are also analysed by employing the finite difference method and the calculated results are compared with the experimental results. The following results are obtained. (1) The cutting temperature reaches to 200°C or more during the diamond cutting. (2) The temperature rise in the workpiece is in the range of 0.1-2°C under the cutting conditions tested. The workpiece temperature increases with increases in the cutting speed, the feed rate and the depth of cut. (3) The temperature distributions in the workpiece calculated are in good agreement with those measured.
In this paper, the straightness of silicon wafer ground by wafer rotation grinding method is discussed, which is caused by the parallel error between grinding wheel axis and rotary table axis. The parallel error is defined by two angles, that is inclination angle θ and direction angle α. And the effect of the parallel error on the straightness is examined theoretically and experimentally. The main results obtained are as follows: (1) The profile and the straightness of the ground surface are largely effected by the direction angle α. (2) The direction angle al exists which makes the straightness minimum. (3) Practically, the straightness is maintained in the lowest level when the direction in which the thermal deformation of surface grinder is maximum is coincide with the direction angle α=0° or α=180°. (4) The straightness is proportional to the inclination angle θ. (5) In this experiment, the variation of the straightness was maintained less than ±1 μm at α_??_180° when the grinding operation was continued in several days using an ordinary surface grinder.
The circular cutting with a single point diamond cutting edge, in which the depth of cut is very small and takes maximum at some point, is carried out for making clear a cutting process of sialon under conditions similar to practical grinding, investigating sliding of a diamond on sialon, chip formation, groove profile, stock removal and so on. Main conclusions obtained in this study are as follows: (1) There are three different regions with depth of cut ; elastic, plastic and cutting region. (2) In the transitional cutting process, there are following three types of interference with maximum depth of cut; (i) elastic region through the contact length, (ii) elastic-plastic-elastic, (iii) elastic-plastic-cutting-plastic-elastic. (3) Chips are formed by plastic deformation as well as brittle fracture. (4) Cracks generated under real interference groove become larger with increases of depth of cut and nose radius of cutting edge.