Turning processes of low carbon steel, high manganese steel and titanium alloy either by a carbide tool or by a diamond tool have been simulated using an existing three-dimensional finite element simulation code. Flow stress characteristics of the workpieces, friction characteristics at the tool-chip interface and thermal properties of the work and tool materials all influence chip flow and tool wear, resulting in different machinability. For instance, the titanium alloy gives rise to the highest rake temperature though the cutting force is smaller than the high manganese steel, which is due to low thermal conductivity of the alloy and high strength at elevated temperature as well. The effect of a coolant has also been investigated. It is more effective to use a high thermal-conductivity tool like diamond or CBN than to use a coolant from the viewpoint of reducing the edge temperature.
The paper deals with some features in cutting mechanism of superfinishing by vitrified bonded fine cubic boron nitride (CBN) stones as applied to hardened bearing steel and their applications for optimizing stone structures and operating conditions. Comparative tests among the equivalent stones of CBN, diamond, aluminum oxide abrasives are carried out. In contrast with the performance by conventional stones in which break-off and loading take place purposely, the CBN stones show stable cutting performance with little tendency to wear and spall on cutting edges. This higher cutting capability, on the other hand, inevitably tends to be associated with rougher surface finish. Along with cutting experiments under the widely ranged operating conditions, carefull SEM observations are executed on the stones and chips removed. To sustain high cutting performance with acceptable surface finish, CBN stones with finer grit size than that employed in conventional ones are recommended to use under the conditions which ensure a stable cutting and fine finish acceptable with little loading by providing suitable small channels on the bond for easy chip removal. The conditions recommended are lower stone pressure, high peripheral speed and a certain optimal inclination angle.
The purposes of the present paper are to investigate the effects of ultrasonic vibration on machining accuracy of duralumin and to make clear the mechanisms for the improvement of machining accuracy in microdrilling. Ultrasonic vibration of 40 kHz considerably reduces the friction on the rake face, makes chips thinner and then decreases cutting forces. This decrease in cutting forces, especially the variation of the mean radial force, leads to the improvement of cutting accuracy, i. e., smaller hole oversize, a little better roundness at hole entrance. smaller displacement of hole center with ultrasonic vibration. The thin chip increases the velocity of chip flow, and results in better characteristics of chip disposal and less tendency of drill breakage.
This paper describes experimental observation and numerical analysis of the arc plasma extinction in the electrical discharge machining (EDM) process. The arc extinguishing time must be shorter than the pulse interval, because it is closely related to the stability of the machining process and hence the machining rate of the process. The spark locations and the waveforms of discharge current and gap voltage were observed in the continuous process in order to distinguish a discharge whose location was influenced by the insufficiently extinguished plasma which was made by the previous discharge. The experimental results show that the plasma extinguishes within 10 micro seconds under the condition that the distribution of discharge location is uniform, so that the machining process is stable. However, in the case that the discharge localization occurs, it takes longer to deionize the arc plasma. The time variation of the plasma temperature after a single pulse discharge was calculated with the finite difference method to estimate the arc extinguishing time. The calculated results show that the arc extinguishing time depends on the temperature of the electrode surface, and so that the local temperature rise causes such a instability as the discharge localization.
In large scale problems of line balancing, a weak point is to spend very effort of calculation when branch and bound method is adopted to solve the result. Therefore, in this paper, they propose the method which can seek the satisfactory result by split the problem into partition. Firstly, problem is divided into several parts, in each part the optimal line balancing is investigated, and then, the results of all parts are jointed together to search the trial solution for the whole part. Lastly, in order to improve the trial solution, line balancing of the union of partitional result is conducted again to search for the satisfactory result. Furthermore, computer is used for the result calculation, the result is compared with the convent ioal method to find the efficiency of this proposed method.
The present paper deals with the relation between the torque and axial tension of screw threads in the elastic-region tightening. The torque on fitted portion of threads and axial tension on the screw threads of M 12 × 1.5 - M 20 × 2.5 are measured by tightening test using a new designed device. The experimental results indicate that these measurement values are related to each other through the general equation that express the relation between torque on fitted portion of threads and axial tension in the screw threads. It is concluded that validity of the equation is confirmed experimentally, but the equation is not applicable when a bending moment acts upon the bolt at tightening.
This paper describes functions that are needed for exchange of curve and surface data by using STEP data exchange system. In some cases, data conversion of curve and surface data must be done using approximation and occurrence of numerical error is inevitable. To predict the case and take suitable measure for it, a detection method is given. Also, an implementation method to detect the error is proposed.
A new methodology for form tolerancing in design object modeling is proposed. At first, what kind tolerances must be prepared and how to describe them in the authors' design object modeler CONMOTO is discussed. Next, the Positioning Performance Requirement (PPR) is defined and its computer description is discussed. Focusing the lines of geometrical error formation inside machine parts, several design rules for suitable tolerancing are derived from PPR using the Related Part_Atom Graph. At last, the computer implementation is shown that aid human designers to put the Surface Trend Indications which the authors have proposed for tolerancing.
A consulting system for the body loads taken on individual joints while working has been developed using a kinetic analysis system of human body motions and a posture input device shaped like a robot, called CHAPLIN (Consultation by HAndling Puppet-Like INterface). CHAPLIN has 15 skeletal segments made of vinyl chloride resin, and 16 total degrees of freedom. The sensors are invisibly imbedded in the resin, thereby allowing the exterior form to be crafted so that postures are easily recognizable. The torques acting at body joints are calculated from the posture inputted to a computer and the consulter's anthropometric data. In the system real-time skeletal animation is displayed with colored visualization of the torque intensity about the joints. Based on both the CHAPLIN's posture and the torque intensity displayed, the consultation is conducted comparing the body loads corresponding to several postures during load liftings. As a result of consultations with 20 subjects, it was found that this system is very useful for enabling workers to understand how to improve their postures.
A method of inspecting geometrical tolerances is important from the economic and qualitative viewpoints in coordinate measuring. However, there are some problems with CMM inspections based on ISO geometrical tolerances, due to the lack of a mathematical representation of the relationship between a toleranced feature and datum systems. No mathematical representation makes it impossible to evaluate the geometrical deviation of the related feature from a measured data set. In the first report, an evaluation method for related features with geometrical constraints in coordinate metrology was proposed. However, the proposed method could not be applied to the evaluation of related features under Maximum Material Condition. An inspection method using a computer model of the functional gauge (called the virtual gauge) is proposed in this report. The relationships between the geometrical elements of related features, datum, tolerance specification, measured data set, and functional gauge are represented in a formal description language EXPRESS. Computer experiments are conducted to verify the results and the validity of this method.
In order to investigate the mechanism of rhythmic motions of the plant, which is self-generated in response to its environment, a new measuring system of the rhythmic motion of the root was developed. This system can automatically record 3-dimensional motions of the root. To measure movements of the root with a high accuracy without actual contact, image processing was applied to this system. Furthermore, in order to examine plant cell turgor pressure changes, which are relative to the rhythm formation, they developed a new measuring system of cell turgor pressures, installed two pressure probes. As a result, about 1, 2h cycle was observed in the rotational motion of roots, using the measunng system. And rhythmic motions at the main root disappeared when its tip was removed. In addition, it was found that turgor pressures of the main root showed periodic changes and that became synchronized with its environments when light and dark cycles, whose period was 2h, was provided.
Parallel mechanism is composed of a platform connected to a fixed base by some linear actuators called struts. The kinematic chains of parallel mechanism are driven by these actuators to its base and has high stiffness and low weight so it can realize high speed and accurate positioning ability. The Stewart platform is one of the parallel mechanism. In serial mechanism, the direct kinematics solution is easy, but the inverse kinematics solution is very involved. The other way, in the parallel mechanism the inverse kinematics solution is easy but the direct kinematics solution is very involved. In this paper, a new method named “origami solution” to solve the direct kinematics solution of Stewart platform is proposed and some basic equations in “origami solution” are conducted. This method is based on the “Geneqc.c” which is a computer program to get roots of general equations. In the last, the method is evaluated by some examples of the Stewart platform. The direct kinematics solution is solved in 0.01mm accuracy in about 1 second calculation time by 32 bit computer.
This paper analytically deals with conditions for only progressive wave generation and describes experimental result from the first trial. In the development of feeding and handling micromechanisms for minute or thin objects such as microparts and fine leaves, it must be carefully considered that the machine must not give damage to them during the works. The object is feeding by the wave traveled on the belt. The undulatory plane is consisted of a comblike elastic belt. The method is called “Source-Sink Displacement Excitation”. Progressive wave is emitted from source actuator at one end of the belt and reflection wave or standing wave can be actively absorbed by synchronous excitation of sink actuator at the other end. Necessary and sufficient conditions are the same amplitude of excitation at both ends and the same phase between excitation and transmitted wave at the end of sink.
A calibration method using rotation angle is proposed for calibrating horizontally articulated robots. An arbitrarily chosen robot axis is rotated with an arbitrarily given rotation angle. The start and end points of the corresponding motion of the robot tool's axes are measured. Calibration is performed based only on the rotation angles and measured points. Horizontally articulated robots, such as SCARA type robots, can then be calibrated automatically without any teaching operation. Simulation was performed to compare analytically the proposed method with the three points and the four points calibration methods. The simulation chooses a rectangular area where each of the above methods is tested to obtain a measure of error between the theoretical and experimental values (arm lengths, initial angles and robot origin). The results show that the rotation angle method produces a smaller error. Also, it was observed that the proposed method converges faster to the theoretical values compared with the three points and the four points method.