Pneumatic hammer instability has been the greatest problem in realizing a high stiffness gas bearing with a large pocket in the bearing surface. The authors have already succeeded in realizing a high stiffness and heavy damping hydrostatic thrust gas bearing with a large pocket by the use of fluid damper. In this paper, the shaft response characteristics and static performances in a hydrostatic pocket journal gas bearing are investigated both experimentally and theoretically. The following conclusions are obtained. (1) Fluid damper has a good influence on the improvement of the trangent motion and the prevention of pneumatic hammer instability. (2) When an impact force acts on the shaft, it is possible to make the amplitude of rigid body as small as that of elastic body. (3) A high stiffness journal gas bearing with a large pocket can easily be realized by the use of fluid damper. (4) As the settling time is greatly affected by the pocket size, the pocket depth must be made as small as the bearing clearance in order to realize the critical damping condition.
One of the simplest way to improve the stiffness of externally pressurized gas bearings is to increase the supply pressure. The purpose of this study is to examine the possibility and practicality of high supply pressure. In the preliminary test with simple circular thrust bearings with a slot restrictor, it proves that the bearing stiffness increases almost linearly with supply pressure as predicted by the theoretical calculation. Bearing stiffness is far improved with a stepped clearance. Pneumatic hammer instability and gas flow rate are not so critical problems for the high stiffness bearings with a small clearance. The effect of deformation of the bearings by high supply pressure can not be recognized in those experiments. It is confirmed that the increase in supply pressure is the simplest and most practical way to improve the stiffness of externally pressurized gas bearings.
An analytical method to get the required profile of a grinding wheel to finish a specific helical gear and the reverse method to get analytically the gear tooth profile to be formed by a specific grinding wheel are proposed. In these methods, not only the value of coordinates at specific points on the given profile but also the value of gradients at that points are needed. Because, for lack of information, one can not get the required profile analytically from only the value of coordinates. The mathematical meaning of the interference between gears and grinding wheels is clarified and the effective mean to overcome the interference is discussed.
A new method of improving the fatigue strength of the steel wire for automobile have been developed. Principle of the new method is thin surface layer annealing of the wire by using the high power density zone of the focused laser beam in the cone shaped focusing mirror. In this method, the laser beam was coaxially irradiated and focused on the wire to anneal it uniformly. Using this laser processing technique, up to 3μm depth of uniform annealing has been realized, which results in degrading the tensile strength. No defect was observed on the annealed surface of the wire. It should be possible to realize the effective manufacturing process of high performance steel wires using this method.
The purpose of this study is to generate higher precision surface of aluminum alloy reinforced by short fibers of alumina experimentally. So, linearly increased depth of cut type cutting is adopted because of being able to vary the cutting force which is concerned with the mechanism of generation of finished surface. As a result, the pore which was caused by fracture and falling-off or falling off thoroughly of fiber was generated in finished surface. As the stress condition around fiber was nearly constant under the same tool geometry, the ratio of depth of pore to the fiber diameter was constant. And, if tool geometry was properly selected with three dimensional cutting, it was feasible to generate the least defect surface.
In this paper the properties of caustic were made clear to apply this experimental method to stress analysis in cutting operations. Under simplified two dimensional conditions, the objects of study are a wedge shaped plane and a half plane with un-uniformly continuously distributing load over loading region. Specimens are made of acrylate resin plate of 3 mm thickness. The caustic patterns formed by reflected lights from the both surfaces of plate are observed and their characteristics with loading conditions are investigated in detail. On the other hand the computational patterns based on optical theory and mapping method are plotted. These two patterns are coincided accurately enough. With obtained results the convenient simple formula to evaluate end values of external load is proposed.
This cutting tool makes drilling and deburring by one machining operation. That is, as soon as drilling of through hole has been finished, the exit burr generated will be removed by the tool itself that has two additional deburring cutting edges. Addition of the edges to spade and twist drills was done. It was made to the cutting part in the case of a spade drill and to the newly produced part by reducing some part of the body in the case of a twist drill. The former is used large hole and the latter is for small hole. For the processing of deburring, countouring control (circular interpolation) in a CNC machining centre was employed. Edge quality of hole after deburring was fine and the effectiveness of this method of deburring for practical use was investigated.
In order to select the optimum cutting conditions including tool failure, the analytical prediction system for time dependence of failure is required. It is very long way to obtain the fracture characteristics of tool material and their change. In the paper an acquisition system of characteristics by a series of rapid cutting tests is proposed. In the system, stress distribution on tool rake face is predicted by FEM based on the fracture shape experimentally obtained.Then the fracture characteristics are also acquired by the time dependence of fracture probability measured. Finally the time dependence of fracture probability is predicted based on the characteristics obtained and compared with experimental results.
In this paper, a new process for finish machining on free-form surfaces is proposed. This process consists of generating CL data, milling an electrode and a work by a machining center, removing cusps of the electrode and the work by electrical discharge machining (EDM) and finish EDM for the work. In the cusp removing process, EDM with planetary motion under high wear conditions is carried out. Powder suspended working fluid is used in finish EDM in order to break through the roughness limit. Since the planetary motion in EDM process decreases geometrical accuracy, the electrode shape is manufactured to compensate its planetary motion. A geometrical tracing method generates tool paths for the work and the electrode without any cutter interference. A shape with mirror-like free-form surfaces has been realized through a series of automatic processes without sacrifice of geometrical accuracy and without any manual works.
Cooling action of grinding fluid is one of the most important work for improving the grinding efficiency, geometrical accuracy, and surface quality. However, there is only a little information on the heat transfer coefficient, α, in the wheel to workpiece contact zone under deep grinding. New technics for measuring α are proposed and measures for improving the cooling efficiency are given. α shows the peak value at the fluid entrance point into the contact zone, and it sharply decreases with the contact length; however, the decreasing rate is less than the theoretically expected. The average value of α in the contact zone is about 2 to 3 times as much as the theoretical because of the starling action performed by cutting edges in the contact zone. To enhance the cooling efficiency especially at the fluid exit point out of the contact zone, it is important to increase the velocity of grinding fluid and wheel speed, and it is also desirable to form shallow grooves on a wheel periphery.
An automatic system has been developed for the measurement of interference fringe fractions by four point method. A parallel and rectilinear fringe pattern made by Michelson laser-interferometer is observed by four photo-detectors. Through four uniformly spaced slits, detectors collect the light of corresponding regions of the fringe pattern, and the output signals are transmitted to a computer after passing through an amplifier and an AD converter. In the computer, an interference fringe fraction at the middle point of two central slits is calculated. Theoretical analysis is made for errors in measured values of fringe fractions caused by the variation of amplification of the detector outputs and the slit spaces. Experiments show the interference fringe fraction is determined in the accuracy better than ±0.005 by this method.
This paper describes a position control method and a control system configuration for newly developed fine motion stage using parallel linkage mechanism. A new static decoupling control method is proposed to compensate interference characteristics of 6-axes stage, including compensation of machine and actuator accuracy. Its decoupling parameters (Jacobian matrix) are calibrated by iterative process, and as a result total decoupling accuracy of 5% is obtained. The control algorithm, which requires complicated matrix calculation, could be executed within 250μs by parallel processing method using multi transputers. By experimental results of step response for each degree of freedom, it is confirmed that proposed decoupling method is more effective than conventional one. Consequently positioning resolution of 0.01μm (x, y), 0.123μrad (θz), response of 30-40 Hz, and dynamic rigidity of more than 12.3 N/μm (x-direction, frequency <40 Hz) are obtained.
Parallel spring is usually adopted for a precise positioning servo system.This mechanism has many resonances of higher order, therefore it is difficult to obtain a wide band and high loop gain servo system. This paper presents a new method to analyze a dynamic characteristics of the mechanism. Many parameters such as the dimensions of the leaf spring, the coordinates of a sensing point, and a force acting point are considered. By this method, it is possible to simulate the behavior of the mechanism and obtain the relations between the transfer function and above parameters. This analysis is verified experimentally to be reasonable. By utilizing the method, a simple servo system and a small-sized actuator with wide band frequency response are realized.
When we measure three-dimensional surface roughness, higher skill is demanded to locate the specimen surface within a range of profilometer. From this need, the authors developed the three-dimensional profilometer to measure micro irregularities of surface by applying a commercial stylus profilometer. The developed system was controlled automatically the orientation of specimen table by the micro-computer. This computer calculates the inclinations of table in X- and Y-directions and the height to keep the diamond stylus in a measuring range. The height was corrected in an accuracy of 0.1μm and the inclination of table in about 0.02μm/mm.
In recent years, the form of production desired in mechanical manufacturing plants is shifting from mass production of a small number of products to small lot production of a variety of different products. Therefore, the realization of effective manufacturing systems suitable for this form of production has become an important desideratum. In this context, attention has been directed toward the solution of these requirement by using “autonomous machines”, i.e., equipment incorporating intelligent functions with a view to decentralized autonomous systems. However, in many cases, the systems so formed are ill-structured and the realization of highly complete “autonomous mechanical systems” at the very commencement of operation is difficult. That is, the machine must be a “mechanical systems with learning function”, possessing the capability of independently learning the pattern of dynamical changes in the operating environment, and updating or refining its own knowledge or operational characteristics accordingly. In the present article, an “autonomous mechanical systems with learning function”, capable of rapid and flexible event-driven or request-driven response to an instantaneously changing environment, is proposed. The basic structure of this type of machine is clarified, and, focussing the discussion upon grinding processes, the methodology of organizing grinding systems with learning function is described.
A high-speed algorithm for the velocity analysis of mechanisms is established in terms of constraints matrix derived from pair-axis-motors and circuit matrix. The constraints matrix of a mechanism with single or multiple closed loops becomes a symmetric matrix whose order is equal to the number of pair-axes in the mechanism. The magnitude ratios of relative velocities at all pairs are determined by the system of homogeneous linear equations with constraints matrix as the coefficient matrix. A FORTRAN program based on this algorithm is created for simulating the motion of deterministic mechanisms. The program was also applied to solve inverse kinematics problem of robot to confirm the computational rate and accuracy of the algorithm.
In order to generate free-form curves passing through given point sequence without solving the simultaneous equations which represent the relationships between the coefficients of curve segments, a method of inserting an extra control point between each two subsequent control points has been developed. Two methods for determining such an extra control point, which is called additional control point, are discussed. First the method for using the approximated solutions of the simultaneous equations is considered. Next a new method simpler than the former ones, which needs not solve the simultaneous equations, is presented. Curves generated by these methods are compared with each other and compared with the curves generated by solving the simultaneous equations.
This paper describes a new method of model-based diagnosis that employs single fault process assumption. This assumption supposes that at most one fault process, which is a causal chain of physical phenomena that does not occur in normal states, will happen to an object machine at one time. By introducing this assumption, causally related multiple faults and the faults that cause structural changes in a machine are detected. Knowledge for diagnosis that is described based on qualitative physics is divided into two kinds; one is the object model that represents structure and characteristics of an object machine and the other is knowledge about principles and laws. In order to diagnose causally related multiple faults and the faults that cause structural changes, knowledge about physical phenomena is described in principles and laws. The algorithm of diagnosis consists of fault search and fault simulation. The former derives candidates of fault processes. The latter simulates behavior of the object machine in which a fault process occurs based on qualitative physics. By comparing simulated fault models with the object machine, the likeliest fault process is identified. An experimental diagnosis system that succeeded in diagnosing about some object machines is also described in this paper.