Key Engineering Materials Vols. 447-448

Abstract: This paper addresses the further developing and utilizing about the functions of EDM machine tool on the basis of researching the numerical controls of EDM machine tool itself. Experiments of testing critical gap distances, single pulse discharges and single pulse discharge gap distances have been performed by the machine tool without any extra help of auxiliary instruments or equipments. The measuring accuracy and repeated testing accuracy is the numerically controlled displacement precision of the machine tool itself. The development of this function would have a great impact on enlarging the utilizations of EDM machine tools, on evaluating the behavior of EDM effectively and on designing the jumping displacement of electrodes reasonably.

Abstract: In this paper a kind of architecture for an energy-saving EDM supply composed of three serial stages in the topology and its practical design are discussed. Various special controllers and its assisted circuits are introduced in the each of the three serial stages. The PFC controller UC3854 placed on the front stage provides satisfactory input power factor of the system. The PWM controller UC3875 mounted on the middle stage realize the closed control of the current of the inductance limiting machining current. An embedded controller PIC16F877 on the final stage is chosen to setting such machining variables as peak current, discharge duration and pulse interval. The communication with host PC is also realized by the same embedded controller. The architecture based on model of multi-controller parallel working guarantees capacity of the system real-time process. The prototype of the energy-saving EDM pulse supply using MOSFET power device is developed. A lot of experiments have demonstrated the feasibility and stability of the practical design.

Abstract: The finishing process of a metal mold depends on the hand work of experts by using a whetstone tool in many cases. This is because it is difficult to treat the three-dimensional configuration, such as free-form surfaces and convex and concave configurations. To overcome this difficulty, we propose a dynamic magnetic field assisted finishing using magnetic compound fluid (MCF) for three-dimensional configurations. In this paper, we demonstrate the MCF slurry (MCF mixed abrasive and cellulose fiber in) under dynamic magnetic field shows the high form restoration and generates the high normal force compared to that under static magnetic field; resulting in shows the high finishing performance. Moreover, we compare and discuss the surface roughness and form accuracy under both static and dynamic magnetic fields against three-dimensional configuration made of high hardness non-ferrous mold steel HPM75, which is used for plastic injection mold.

Abstract: In the micro EDM method by electrostatic induction feeding, a pulse generator is coupled to the tool electrode by a capacitor, since the negative influence of the stray capacitance in the circuit can be eliminated, and the discharge energy per pulse can be minimized, thereby realizing discharge craters of nanometer order. However, there is still the stray inductance in the discharge circuit, other than the stray capacitance. In this study, in order to examine the influence of the stray inductance, experimental investigation was conducted.

Abstract: This paper describes machining characteristics of high spindle speed WEDG using the electrostatic induction feeding method. In this method, non-contact electric feeding allows the workpiece rod to be rotated at a high speed of up to 50000rpm. Since the temperature rise on the workpiece surface is low, the material removal rate was two times higher and the surface roughness was also improved compared to the normal RC discharge circuit where the rotational speed was 1000rpm at the highest due to contact electric feeding using a brush. Furthermore, micro rods thus prepared were used as tool electrodes to machine micro-holes with the same rotation speed of 50000rpm. It was found that smaller gaps and better straightness can be obtained due to the high flushing efficiency at the high spindle speed.

Abstract: We present simple deterministic process models for the prediction of the evolution of the cross-sectional profile of glass channels generated by erosive wear in micro air abrasive jet machining using a round nozzle. The present work was motivated by a need to understand the sensitivity of the geometry of the generated cross-sectional profile to the degree of offset between the centre of the nozzle and the centre of the mask defining the channel. Experiments were carried out on soda lime and borosilicate glass to verify the process models. Predicted results show fairly good agreement with experimental results. We conclude that, without proper alignment, the cross-sectional profile is easily skewed, as the micro abrasive jet machining process quickly acts on any initial geometrical skewness and compounds it over time.

Abstract: Diode lasers have become an important tool for polymer welding in automotive industries, in medical and electronics manufacturing. High efficiency and well fitting beam quality make them a perfect tool for industrial applications. With adapted optics it is possible to fit the laser spot shape to the geometry of the work piece. Galvo scanners are the most flexible tool to apply local and precise dose of heat to the work piece. If this flexibility is not needed, the laser spot can be customized by optics to line, circular or arbitrary shaped geometries. For joining transparent parts either an absorbing layer or diode lasers with a wavelength of 1940 nm can be used.

Abstract: This paper aims to introduce the performance of bunched-electrode for die-sinking EDM. Bunched-electrode was formed by bunching numerous hollow cell-electrodes together to generate an electrode in which end surface matches the final surface of the mould cavity. FEM analysis and experiments were conducted to demonstrate the feasibility and effectiveness of bunched electrode in ED machining. Experiments show that while machining with bunched-electrode, it is feasible to apply a much higher peak current to achieve higher MRR. Meanwhile, a special phenomenon called shallow radial craters in machining with bunched-electrodes was observed and analyzed. One possible reason may be that the plasma columns in the gap are distorted outwards by strong inner pressure flushing.

Abstract: Currently CAD/CAM systems have become more common in automated manufacturing to enhance accuracy and efficiency. However, machining efficiency and accuracy are mainly relied on the experience of the engineer. Therefore, in this research the main aim is to propose the system which automatically analyzes the characteristics of a CAD model and to extract manufacturing features. The method for analyzing shapes of a CAD model represented by triangle mesh is studied. The system can extract planar, spherical, cylindrical, hole, arc, and other curved regions. This research will improve the integration of CAD, CAM system, and is supposed to have a great potential in the application of manufacturing and other engineering fields.

Abstract: In recent years, five-axis controlled machine tool attracts attention from the increase in demand for improvement of productivity. Five-axis controlled machine tool which is added two axes for rotating and tilting to three translational axes, and can give arbitrary tool attitudes for a workpiece.