This study is carried out to investigate the wear mechanism of print wire and the criterion for the material selection of print wire. The results obtained are summarized as follows: (1) The wear of print wire is caused mainly by the abrasive action of carbon black particles included in ink ribbon. (2) The print wires of high hardness have high resistance to wear. (3) The print face corner of wire is rounded slightly by the effect of high contact pressure as compared with the central portion.
It is very important to estimate the chip curl diameter and/or the chip curl direction for the chip control. In this paper, the side flow of the chip in orthogonal cutting and turning is experimentally observed, and the relation between the value and various chip forms in turning is investigated. Using the value of the side flow in orthogonal cutting, the method to estimate the curl diameter and the curl direction of the chip in conventional cutting is also described. The results obtained are as follows. (1) The data of the chip width and the chip thickness in orthogonal cutting are available to estimate the values of the side flow in conventional cutting. (2) The chip curl diameter and the chip curl direction calculated by the values of the side flow agree well with the experimental results. (3) This analytical method can be applied to estimate the chip forms in conventional cutting for various cutting conditions (depth of cut, feed, etc.) and tool geometries (corner radius, approach angle).
Temperature analysis based on temperature-dependence of thermal properties (specific heat and thermal conductivity) is carried out using numerical calculations. An explicit form of finite difference method was adopted; for constant thermal properties, target size effect is strong compared with the case where properties vary with temperature. For the same sizes, the target of properties varying with temperature is heated more rapidly than that whose properties are independent of temperature; for 2.08 mm radius and 1.06 mm thickness carbon steel, times required to raise the temperature at center point by 1 300 K by a beam of 1 kW power and 1 mm radius are 2.78 and 1.77 ms for the former and the latter, respectively. Under a fixed treatment time, isothermal planes extend more widely in the target whose properties depend on temperature than in that of constant properties. To obtain heat treatment conditions, the consideration based on temperature-dependence of thermal properties must be done.
In the present study, the following results were obtained when high purity alloys of Al, Al-Cu, Al-Mg, Al-Mg-Zn and OFHC were cut with a natural single crystal diamond tool and a synthesized diamond tool, set at an angle θ and with varied edge radii. (1) The best value Rmax of surface roughness is obtained when the tool is set at an appropriate angle θ. (2) The appropriate tool setting angle θ, stated in (1) above, varies according to the purity of the material to be cut and the amount of alloy atomic elements. (3) The θmin value is determined upon proper balance between the banishing and cutting actions of the cutting tool. (4) When mirror finish is required, an ultra precision cutting tool with the edge redius fixed closer to a straight edge is better suited to generate a good machined surface. (5) While the natural and synthesized diamond tools, when compared, do not show a great difference in geometric accuracies such as surface roughness and flatness, there is a difference in the dominating factors of the cutting mechanism such as the cutting force and the friction coefficient of the tool rake face. (6) The shearing stress of a natural single crystal diamond tool indicates an overall value smaller than that of a synthesized diamond tool.
Peripheral and face turning processes with a segmental cathode were studied under conditions of constant cell voltage and feed rate. Relationships between the machining gap width and process variables, such as feed rate, duty factor, rotation rate, etc., were described theoretically. Experiments were performed to verify the model. Type 304 stainless steel and a nickel-base superalloy, Hastelloy X, were machined in a 3 mol/dm3 NaNO3 electrolyte at 30°C. Results show that equilibrium conditions were established in peripheral turning with a tapered cathode and in face turning, although the process becomes intermittent by using a segmental cathode. In peripheral turning with a parallel cathode, the process has no equilibrium condition because of no relative feed of the cathode to the workpiece. The rotation rate has no effect on the machining gap width, except for the rates less than about 5 rpm. The final workpiece diameter during peripheral turning is determined primarily by the inclination angle and length of the cathode, while other variables have only a secondary importance on it. For face turning, a simple equation between the equilibrium gap width and process variables was derived by using an effective feed rate defined as a feed rate divided by a duty factor.
This report describes a three-dimensionally and numerically controlled electric discharge machining (EDM) system which is newly developed in order to solve a serious problem of the tool electrode wear in the contouring EDM. In order to obtain higher accuracy in machining this system comprizes faculties of both accurate monitoring of the deforming process of the electrode due to wear and automatic compensation of tool path. Shapes of the tool electrode are standardized into a cylindrical form and the constant rotation is given to the electrode to make the electrode wear axis-symmetric for facilities of the measurement. The shape of the worn electrode is measured periodically during machining process by using automatic touch-sensing mechanism, and proper compensation is given to the tool path in each time. Main results are as follows : (1) Various contours including corners are formed with high accuracy, and spherical contours are also obtained only by changing the machining programs. (2) By utilizing the deformed shapes of the worn electrodes smoothed surfaces as well as corners with small radius are obtained. (3) The deformation process of the electrodes is clarified.
Although Al2O3 ceramic tool shows an excellent performance in machining of FC (gray cast irons), it does not in machining of FCD (nodular cast irons). In this paper, cutting tests and reaction tests were conducted to find out the cause of the above phenomena. As a result of the cutting test, it was found that the matrix, carbon shape and hardness of the work material had little effects on the wear of the Al2O3 ceramic tool. And the difference in machinability of the two kinds of work material was presumed to be attributed to the reaction between tool and inclusions in work material. Therefore the reaction test was conducted between Al2O3 and MgO and the other oxide inclusions. As a result, it was found that MgO diffuses into Al2O3 ceramic tool and makes spinel called MgO·Al2O3, which decreases the wear resistance of the tool. Further, a new type of ceramic tool which was mainly made of carbides has been produced as a trial tool for FCD and its cutting performance was tested. The carbide ceramic tool showed twice as longer life than Al2O3 ceramic tool in machining of FCD.
Many characteristics and evaluative factors of machine-tool dynamics often interact mutually, and competitive and cooperative relations exist between them. In order to improve the product performance of machine tools, and finally optimize it, those relationships should be clarified. In this paper, competitive and cooperative relations between evaluative factors of machine-tool dynamics are analyzed. The main results are as follows. (1) Minimization of the maximum receptance value is established on the Pareto optimum solution set for minimizing both the total weight of the structural members on the static force loop and the static compliance. (2) A competitive relationship between minimization of the maximum receptance value and minimization of the static compliance is reduced by minimizing the ratio of the greatest modal flexibility to the static compliance. (3) Minimization of the ratio of the greatest modal flexibility to the static compliance is cooperative with maximization of the damping ratio.
This paper describes user-friendly man-machine interface for drawing pictures, as well as the principles and picture data construction for direct input by hand. Color shaded pictures can be drawn using the CARP rendering system and the drawing time for completing pictures is reduced. Drawing by hand using man-machine interface is considered. Moreover drawing procedures and input methods are classified and personal drawing methods are summarized. It is most important to clarify line drawing input and modification method by handwriting. We used a characteristic point method for recognizing line drawing and realized to make drawing data. This input method was added to the CARP system and drawing experiments were done. As a result, designers can take advantage of greater flexibility in input methods and they can draw pictures more precisely by computer than by conventional method.
This paper describes the study on the SCARA robot motion. The accurate motion control of the robot becomes more important as it is introduced to various kinds of works, especially the robot is used in continuous path control mode. But there are many kinds of factors lying down in the robot motion. They are very complicated, and it is not so easy to find out the factors of robot motion error. In this report, the method applying the experimental measurement and the numerical simulation jointly, is taken to find out the factors. In conclusion of the application, it is pointed out that the main factor of the SCARA robot motion error is the delay of two motors controlled by servo system. The positional error of the tool point path is mainly caused by the delay unbalance of two motors which actuate the first and the second arms.
The purpose of this paper is to analyse the basic characteristics, which include the hydrodynamic effect caused by the high rotating speed of the spindle, and to propose the optimal design principle which attains the maximum stiffness of the bearing. The finite element method with the Galerkin criterion is applied to solve the nonlinear Reynolds equation, and the pressure distribution of the lubrication film is numerically caculated.
Thermal deformation characteristics of machine tools are quite different with each other, and they greatly depends on their machining accuracies requested. Meeting on their characteristics and machining accuracies, many temperature control methods have been developed to improve them. This paper deals with selection of temperature control methods suitable for machine tools with various characteristics. Every temperature control method is evaluated in its temperature deviations and cost. From this study charts which show the controllable and suitable range of every method for machining centers and lathes with different thermal deformation characteristics.
The pin position of print hammer is an important design factor, affecting both impact force and the hammer vibration after collision. The former is a main factor determining the density of printed dots, and the latter plays an important role in determining the returning time of hammer to the home position. In this paper, impact force and the energy of each vibrating mode are calculated for two typical hammer structures varying the pin position over several parameters. It is found that the print hammer normally acts as a two-degree-of-freedom vibrating system, and the pin position has an optimal range where the impact force is appropriate for clear printing, and higher order modes of vibration are effectively suppressed.
Screw rotor profile in the compressor is one of the significant factors affecting the efficiency and the manufacturing cost. The conventional screw rotor profile has made it difficult to reduce the manufacturing cost and to improve the precision, which affects the efficiency, due to the poor machinability. A new rotor profile having following advantages ; (i) higher productivity and precision due to more suitable profile for hobbing the rotor, (ii) smaller blow hole area and (iii) lower leakage loss. Based on the new rotor profile, an advanced oil injected screw compressor has been developed, which can achieve higher efficiency and lower manufacturing cost than those of the conventional compressor.
Design information on a new type of aerostatic lead screw is proposed. To avoid the occurrence of pneumatic hammer, a surface restriction system is employed. The surface restriction can be provided by stepping the flank of the internal thread. The pressure distribution on the flank is analysed by using the Finite Element Method, and the virtual bearing area is calculated by integrating the pressure over the flank. It is shown that the virtual bearing area increases as the gas film thickness decreases. From the relationship between the virtual bearing area and the gas film thickness, the thrust stiffness of the lead screw is calculated. According to the proposed design method, an aerostatic lead screw with the following specifications is made ; outer diameter of the male screw 51 mm, flank angle 15° (trapezoidal thread), pitch 16 mm, flank width 8.28 mm, step width 3.86 mm and step depth 10 μm. The maximum thrust stiffness is 10.3 N/μm, where the air supply pressure is 0.49 MPa and the gas film thickness is 9 μm. Though the measured thrust stiffness is slightly lower than the calculated value, it is high enough for using the aerostatic lead screw as the lead screw of the feed drive devices.
An unbalanced grinding wheel produces an uncompensated centrifugal force which induces a relative vibratory motion between wheel and workpiece. The visible chatter patterns which often occur on ground surfaces are attributed to this relative motion. Therefore, the periodical balancing of the grinding wheel is necessary to produce good surfaces. Two methods, which are applying the principle of centrifugal balancing, and are named Nomograph method and CAB method, have been developed. After the balancing operation by these new methods the residual unbalance was measured. The results of the experiments indicate that the Nomograph method is capable of balancing handily without trial and error and the CAB method is practicable to reduce the residual unbalance nearly to the noise level of measuring instrument.
This study aims at development of the simple design method of stress analysis of bolted joints applicable to the general case. The multi-bolted joint is modeled using spring-beam elements and analyzed with finite element method. The relationship between the applied load and the stress in the bolt is analyzed. The axial stress and the bending stress on the bolt are measured by strain gages to verify the results from analysis of the multi-bolted joint of various geometry. The obtained results are as follows: (1) A simple and useful method to analyze the stress in the bolt in the multi-bolted is proposed. (2) The analytical results show good agreement with the experimental results. (3) When the external force acts on the bolted joint, the stress in a bolt near the application point of the force is increased. (4) Even if the distance between the bolts is large, the stress in a bolt near the application point of the force is not so relieved.