Papers by Keyword: Electric Discharge Machining (EDM)

Abstract: The effects of discharge parameters on micro-surface topography in mirror-like surface electrical discharge machining (EDM) process were investigated, and the optimization scheme was obtained. The realization of the process parameters and their effects were analyzed by the Taguchi method. The surface roughness amd 2D micro-surface topography were measured. An L16 (44×23) Taguchi standard orthogonal array was chosen for the design of experiments. The level of importance of the parameters parameters on surface roughness was determined by using analysis of variance (ANOVA). The experimental results confirmed that peak current and open discharge voltage have more influence on the surface roughness on mirror-like surface EDMed workpiece in comparison with pulse duration and pulse off-time.

Abstract: The debris re-adhering on the machining surface will affect the workpiece precision in EDM; therefore, the main purpose of this research is to study the re-sticky phenomenon of the powder metallurgy (PMM) in EDM. PMM with different melting points from 1450oC to 3410oC were used as EDM materials, the copper and the tungsten were chosen as the electrodes. The polarity in EDM was depended on the pole of the electrode. For observing the re-sticky position of the debris, the electrode was set no rotation or with 200 rpm rotational speed in EDM. The results showed that the melting point of PMM did not exceed 3000oC (PMM did not contain tungsten); the debris of PMM would not re-stick on the working surface no matter what polarity was used in EDM. However, only negative polarity can cause the re-adhesive effect when the melting point of PMM exceeded 3000oC. The debris would re-stick on any machining position when the electrode was not rotated in EDM. However, the debris would adhere on the central of the working area with 200 rpm rotational speed of the electrode.

Abstract: In electrical discharge machining (EDM), material is removed by a series of electrical discharge between the electrode (tool) and the workpiece that develops a temperature of about 8,0000C to 12,0000C. Due to high temperature of the sparks, work material is melted and vapourized, at the same time the electrode material is also eroded by melting and vapourization. Electrodes wear (EW) process is quite similar to the material removal mechanism as the electrode and the workpiece are considered as a set of electrode in EDM. In the present study effort has been made to reduce EW by cooling, using liquid nitrogen during the EDM of titanium alloy. Investigation on the effect of cooling on electrode wear (EW), material removal rate (MRR) and surface roughness (Ra) of the workpiece was carried out. Current (I), pulse on-time (ton), pause off-time (toff) and voltage (v) were considered as the machining parameters. Design of experiment (DOE) was used to design the experimental works. Cooling of electrode by this technique reduced the melting and vapourization of electrode material and enhances electrode life. It was possible to reduce EW up to 27% by applying this technique while MRR and Ra were improved by 18% and 8% respectively.

Abstract: Based on a self-developed pulse power supply, effects of working fluid to machining efficiency and relative wear of electrode are studied. tangent-hole machining experiments are designed and carried out. Tangent holes with 0.75mm and 0.56mm diameters on some nozzles are obtained.

Abstract: In order to manufacture geometrically complex or hard material parts, a new kind of multi-axis electro-discharge machining (EDM) computer numerical control (CNC) system, which is based on RT-Linux platform, was presented. Dual-kernel structure of System is adopted: Linux and RT-Linux are used to realize Time-sharing tasks and Real-time tasks separately. The system is divided macroscopically into two parts: Real-time part and Time-sharing part, microcosmically into three modules: Real-time Control Module, Drive Module and CNC User Module. Through the communications among them, three modules construct the whole system. Rimed Turbine Blisk was experimentalized to validate the performance of the system. The process and the results implied that the system is Real-time, stable and reliable.

Abstract: The topography errors of micro electrical discharge machining (micro-EDM) surface are mainly composed of surface roughness, surface waveness and profile error. These three errors influence the workpieces functions and performances in varying degrees. Thus, how to pick up these compositions without distortion is very important for surface comprehensive topography evaluation. In this paper, the roughness of micro-EDM surface contour lines is separated by wavelet method. Firstly, it is certified that any curve line could be indicated by different frequency parts with multi-resolution analysis, which is the feasibility study for roughness separation with wavelet method. Then, the mathematical model of roughness separation of contour lines is set up. Finally, the formula of roughness separation times with wavelet theory is given.

Abstract: The two disadvantages of EDM are the low material removal rate (MRR) and poor surface quality. In this investigation, EDM assisted by magnetic field (MFEDM) has been proposed for the first time to overcome above-mentioned disadvantages. Constant magnetic field was applied to the both sides of discharge channel perpendicularly to form a novel process. In experiment, EDM machine tool D703F was used to machine nonferromagnetic materials. The machining parameters discharge current and pulse duration were chosen to determine the effects on material removal rate and surface roughness.Experiment results indicate that the MRR of the combined machining is 1.2~3 times of EDM’s one. Furthermore, the value of surface roughness is also reduced. Therefore, the introduction of magnetic field to EDM has important academic and practical values to the development of EDM.

Abstract: With the necessity to improve the teaching techniques of the processing technologies, in the present paper is showed the development and implantation of a application software that will serve to aid the student of the electro discharge machining process in the decision making process planning this non-conventional manufacture method. This application software manages the totality of the electro discharge machining process, in the die sinking case, by means of the creation of a data base with the necessary parameters of machining. To do these specific tasks, this application makes the data acquisition in analytical form of the machining values that the student tries to reach and has also a graphical environment form to define the geometry of the wished cavity. Finally it exposes the results in a didactic form expressed in a sheet of manufacture operations..

Abstract: A reversible machining method using micro electrical discharge machining (EDM) was developed. This new method can achieve depositing or selective removing of metal material for the fabrication of micro structures. It is easy to transform the machining process from deposition to removal in one EDM machining system. In micro EDM deposition process, brass, tungsten and steel material can be deposited successfully. The deposited material has compact fine texture and combines close to workpiece. Then, micro complex structures by series deposition strategy and sub-deposition strategy were deposited. In the selective removal process, the machining effects of different working mediums were researched. Results show that the machining effect in liquid medium is better than that of in air. Finally, using the micro reversible EDM process, a micro square column with 0.070mm in side length, 0.750mm in height and a micro cylinder with 0.140mm in diameter, 1.180mm in height were fabricated.

Abstract: In micro electrical discharge machining (micro-EDM) of deep holes, the debris dispersed in gap may increase the possibility of secondary discharge, resulting in electrode shape changing and low accuracy of machined hole. In this paper, the debris movement caused by flow fluid in the machining gap is analyzed to understand the mechanism of debris transport by using software, FLUENT. Comparison of debris movement calculated by the modified N-S equation and N-S equation is conducted. Debris movement calculated by the modified N-S equation is demonstrated to be correct by experiment. The simulation results can explain the phenomena such as subulate electrode and hole, unstable machining process and low machining speed in micro-EDM of deep holes. It is helpful to improve the process of micro-EDM.