Electrical Discharge Machining Technology Research Articles

Development of a combined machining method using electrorheological fluids for EDM

Abstract The objective of this study is to develop a new combined technology of electrical discharge machining (EDM) with polishing by using electrorheological (ER) fluid as working fluid. The surface of the work-piece after EDM has a recast layer with many micro-craters and cracks. Therefore, the polishing process is usually required after EDM for the molds applied on computer, communication and consumer electronics (3C) industries. In the study, we proposed a novel method of EDM that used ER fluid instead of water or oil and employed fine abrasive grits to carry out the combined process of EDM and polishing. The effect of this new electromechanical process combining EDM and polishing was investigated. The experimental results demonstrate EDM process still can perform in the ER fluid and polishing process can be surely performed after adding the alumina abrasives. We have a good performance to obtain surface roughness of Ra 0.08–0.06 μm when using alumina abrasives of 0.3 μm and discharge capacity of 0.01 μF in the proposed method.

Electrical discharge machining using simple and powder-mixed dielectric: The effect of the electrode area in the surface roughness and topography

Electrical discharge machining (EDM) is one of the most widely disseminated manufacturing technologies, in particular as regards the generation of accurate and complex geometrical shapes on hard metallic components. Nevertheless current EDM technologies have major limitations when dealing with fine surface finish over large process area. Indeed this is one reason that explains the need of final manual polishing of mould cavities performed by EDM. Recently EDM with powder-mixed dielectric (PMD-EDM) has been a focus of an intense research work in order to overcome these technological performance barriers. This paper presents a research work within the objective to acquire deep knowledge on EDM technology with powder mixed dielectric and to compare its performance to the conventional EDM when dealing with the generation of high-quality surfaces. In particular the analysis of the effect of the electrode area in the surface quality measured by the surface roughness and craters morphology was carried out for both technologies. The results achieved evidenced a linear relationship between the electrode area and the surface quality measures as well as a significant performance improvement when the powder mixed dielectric is used.

Methodology for developing technological tables used in EDM processes of conductive ceramics

Abstract In the electrical discharge machining (EDM) process of ceramic materials, the adequate selection of process parameters is an especially important factor to take into account. These conditions will determine technological properties, such as surface roughness, material removal rate (MRR) and electrode wear (EW). By means of the technique of design of experiments (DOE), as well as techniques of multiple linear regression, it is possible to obtain technological tables that will allow the programming of the numerical control units used by the EDM machine tools. This is done by employing two different machining strategies in order to achieve a specific surface quality on the parts: one that minimises the electrode wear and the other that maximises the material removal rate, that is to say, the process speed. This has a great deal of interest from a technological point of view as, at present, these types of tables do not exist in the case of ceramic materials, because of the very recent application of the EDM technology to this group of materials.

Study on Finishing Cut with Dry WEDM

Utilizing gas as the dielectric instead of dielectric liquid has enabled the development of dry wire electrical discharge machining (WEDM) technology for finishing cut. This paper studies on the surface quality of tool steel with WEDM method, which is conducted in gas to improve the accuracy of finishing cut, and compares the surface quality in atmosphere and in water. Experiment results showed that Low-Speed WEDM in atmosphere offers advantages such as better straightness, lower surface roughness and shorter gap length, but WEDM in atmosphere has poorer material removal rate than conventional WEDM in water. It was also found the removal rate in atmosphere can be improved by increasing the wire winding speed.

Research on Highly Efficient EDM Pulse Power Supply and Its Experiments

Their efficiency and their power factor of conventional independent electrical discharge machining (EDM) pulse power supplies with the current-limiting-resistor circuit is so low that they do not meet the need of advanced EDM technologies. The design of highly efficient EDM pulse power supply based on switching circuit pulse width modulation current closed-loop principle has been initiated. It is composed of such three stages as a single-phase active power factor correction preregulator, a full-bridge phase shift resonant converter based on machining current closed-loop control and a pulse generator based on machining sequence control. Therefore, the efficiency of the new system is considerably increased to about 70%, its weight and size is decreased much. Its power factor is a great deal increased to about 0.95. Experiment results have demonstrated that the highly efficient EDM pulse power supply is capable of low electrode wear, high speed, stable machining.

Machining of micro/miniature dies and moulds by electrical discharge machining—Recent development

Mass production of micro or miniature parts is increasingly based on replication technologies, such as hot embossing, micro-injection moulding, and bulk forming. These technologies rely on the applications of high thermal and mechanical loads on the forming tools and especially on the integrated microstructures. To achieve sufficient tool life, functional tool materials like hardened steel or cemented carbide are used. The mechanical properties of these materials are a limitation to the variety of structuring technologies which can be applied. Due to their non-contact thermal material removal mechanism electrical discharge machining technologies offer a suitable alternative, in terms of obtainable structure dimensions and accuracy. This paper presents an overview on the state of the art of applicable micro-electrical discharge machining technologies for applications in the field of micro/miniature die and mould making.

Advancing EDM through Fundamental Insight into the Process

This paper aims to show the prospects of electrical discharge machining (EDM) technology by interrelating recent achievements in fundamental studies on EDM with newly developed advanced application technologies. Although gap phenomena in EDM are very complicated and hence not yet very well understood, recent improvements in computers and electronic measuring instruments are contributing to new discoveries and inventions in EDM technology. Such newly acquired insight sometimes raises questions on the validity of the established theories of EDM phenomena, and EDM processes once believed to be impossible or unrealistic are now becoming practical.

A Surface Modification Method by EDM and Its Application to Cutting Tools

This paper describes a new surface modification method by Electrical Discharge Machining (EDM) to create a hard ceramic layer on the workpiece. When a kind of metallic material that makes hard carbide is used as an electrode of EDM, hard ceramic layer can be deposited in a certain condition in the process of EDM. In this paper, characteristics of the layer and the application of this method to cutting tools are discussed. First, the principle of this surface modification method is shown. Secondly, the characteristics of the layer are studied in detail. Through the discuss of wear characteristics of the electrode and formation characteristics of the layer, it can be found that there are some distinct differences between the traditional EDM technology and this new EDM surface modification method. Thirdly, the micro-hardness test of the layer at the different distance from the base metal is carried out. It shows that there is a hard area also under the surface of base metal. At last, as an application of EDM surface modification method, cutting test of cutting tools is done, and it confirms that the life of the cutting tool by EDM surface modification is much longer than that of without layer.

331 絶縁体包覆金属線電極による金属への深穴放電加工とその高速化(OS2 放電加工)

We are proposing a new electrical discharge machining technology for a fabrication of deep, narrow hole in metal. This system employs as the tool electrode a wire encased in a dielectric pipe jacket instead of a conventional pipe electrode. The dielectric jacket prevents secondary discharges occurring between the.sidewalls of the wire and the fabricated hole, enabling a fabrication of a deep, narrow hole without a precise electrode-driving mechanism. However, the fundamental knowledge and the practical techniques in operating this system are insufficiently acquired. In the present study, we described the optimization of electrical conditions to better machining performances. We mentioned also the machining speedup by use of a capacitor and electrolytic working fluid.

Study on modeling of wire EDM process

Wire electrical discharge machining (WEDM) technology has been used widely in production, aerospace/aircraft, medical and virtually all areas of conductive material machining. Its complexity and stochastic nature have stimulated numerous attempts to model it accurately. This paper presents an attempt at modeling the process through Response Surface Methodology and Artificial Neural Networks. A response surface model based on a central composite rotatable experimental design, and a 4-16-3 size back-propagation neural network have been developed. The pulse-width, the time between two pulses, the wire mechanical tension and the injection set-point are selected as the factors (input parameters), whilst the cutting speed, the surface roughness and the surface waviness are the responses (output parameters). The two models are compared for goodness of fit. Verification experiments have been carried out to check the validity of the developed models. It is concluded that both models provide accurate results for the process.

Study on a new kind of combined machining technology of ultrasonic machining and electrical discharge machining

An analysis on the mechanisms of ultrasonic machining and electrical discharge machining has been carried out, and a technology, which combines the advantages of both of them, has been proposed in this paper. It can be used to machine all conductive hard and brittle materials with high efficiency and surface integrity. The mechanism of this combined technology has been studied by the authors. The experimental results show that the efficiency of it is over three times greater than that of ultrasonic machining, and the surface integrity is not significantly different.

A study of ultrasonic-aided wire electrical discharge machining

An investigation has been made into the combined technology of ultrasonic and wire electrical discharge machining (W-EDM), in which the design of the vibrating device is described. The theory to describe the vibration modes of the wire under the action of ultrasonic has been established. Experimental results show that wire vibration induced by ultrasonic action has a significant effect on the overall performance of the W-EDM process. It was found that there exists an optimum relationship between the vibration amplitude of the wire and the discharge energy, by which the highest cutting rate and the best machined surface quality can be obtained. In addition, ultrasonic vibration reduced the residual tensile stress of the machined surface.

Parametric optimization and surface characterization of wire electrical discharge machining process

Wire electrical discharge machining (WEDM) technology has been widely used in conductive material machining. The WEDM process, which is a combination of electrodynamic, electromagnetic, thermaldynamic, and hydrodynamic actions, exhibits a complex and stochastic nature. Its performance, in terms of surface finish and machining productivity, is affected by many factors. This paper presents an attempt at optimization of the process parametric combinations by modeling the process using artificial neural networks (ANN) and characterizes the WEDMed surface through time series techniques. A feed-forward back-propagation neural network based on a central composite rotatable experimental design is developed to model the machining process. Optimal parametric combinations are selected for the process. The periodic component of the surface texture is identified, and an autoregressive AR(3) model is used to describe its stochastic component.

Novel computations of a moving boundary heat conduction problem applied to EDM technology

A computational procedure is presented to solve a model for thermal conduction which properly describes erosion rates for the anodic material in electric-discharge machining (EDM) processes. The shape and size of melt craters obtained by electric sparks in EDM are calculated numerically by use of a model for thermal conduction. The computational procedure is based on the exact solution of the associated problem of 2-D transient conduction in a semi-infinite body subjected to a uniform time-dependent heat flux over a small circular part of its surface. The superposition principle in conjunction with adjustable heat sources is used to cope with the time-dependent boundary conditions. Stability is not a consideration in the present method, which requires less computational time than other methods, particularly for long-time solutions. Because discretization of time or space is not used, the present method can be used to calculate the temperature at any location and time. In contrast, finite-element or finite-difference methods must compute all of the nodal temperatures at each time step. These constraints may lead to schemes that become either inaccurate or unstable, or introduce spurious oscillations in the solution for a domain of a realistic grid-size. The method is in general more complicated to formulate and more tedious to program, but is less costly in the numerical implementation and faster compared to other numerical methods.