Effect of Materials on the Mechanism of Electric Discharge Machining (E.D.M.)

Abstract

Electric Discharge Machining process is investigated both theoretically and experimentally to determine the effects of electrode materials on the machining performance. For this purpose a single and isolated spark is physically and mathematically modelled, and its three phases; viz., Breakdown, Discharge and Erosion are investigated. Resolidified electrode materials as suspended particles in the dielectric liquid are found to be the most significant factor in the breakdown phase. Mathematical expressions relating the time lags to particle concentration are given which can be used to determine the effects of particle concentration on the machining performance. Discharge properties are shown to be dependent on the discharge medium which includes vapours of the electrode materials. The polarity effect has been studied both theoretically and experimentally. Some qualitative explanation is given for the erosion phase. Importance of electrical forces is discussed and a simple mathematical expression is given for the erosion phase. It is concluded that optimum machining conditions can only be obtained by proper selection of the tool material, workpiece material and discharge medium since they affect the initiation and development of the discharge and erosion of electrode materials.

Experimental and finite element analysis of EDM process and investigation of material removal rate by response surface methodology

“…Its growth depends on various parameters such as electrode material, pulse current, pulse on-time, and polarity. Different equations have been reported by researchers to identify how spark radius grows during pulse on-time [8,18,20]. From literature survey and as reported by several researchers [16,17,25], a semi-empirical equation (Eq.…”

Thermal Model for Laser-Induced Discharge Surface Strengthening

“…Erden 14 showed that the discharge channel is influenced by the discharge power and time. For a rectangular pulse, the following empirical relationship is suggested for the discharge channel radius for selected pairs:…”

Computer simulation of performance of electrical discharge machining operations

“…Although as said before a large number of phenomena occur during the removal process, it is commonly accepted that the most important one is the thermal effect (Van Dijck 1974, Jilani and Pandey 1982, Erden 1983, Singh and Ghosh 1999. Therefore, basic modelling of the EDM process involves placing and solving the heat transmission problem (see Equation 1) assuming a heat input given by each one of the sparks that occur during machining.…”

“…Pérez (2007) has observed that for pulses with duration of 50µs and intensity of 5A the crater represents about 35% of the total molten volume. Erden (1983) established that the ejecting efficiency depends on the thermal expansion coefficient of the electrode material, the amount of molten material, the F o r P e e r R e v i e w O n l y discharge channel radius, the thermal properties of material and the dielectric flushing conditions. Takezawa (2007) performed a study on single discharge machining with a low melting temperature alloy in order to investigate the material removal mechanism involved in EDM.…”

“…'Although as said before a large number of phenomena occur during the removal process, it is commonly accepted that the most important one is the thermal effect (Van Dijck 1974, Jilani and Pandey 1982, Erden 1983, Singh and Ghosh 1999. …”