Electric Discharge Machining

ELECTRIC DISCHARGE MACHINING INTRODUCTION * Sometimes it is referred to as spark machining, * Its a manufacturing member whereby a desired shape is obtained using galvanical discharges (sparks). * Material is distant from the workpiece by a series of rapidly recurring current discharges surrounded by two electrodes, separate by a insulator liquid and subject to an electric voltage. * One of the electrodes beast-electrode or tool or electrode. * Other electrode workpiece-electrode or workpiece. As distance between the two electrodes is reduced, the current intensity becomes greater than the strength of the insulator (at least in some points) causing it to break. * EDM is a machining method primarily used for unvoiced metals or those that would be very difficult to machine with traditional techniques. * EDM typically works with visibles that ar electrically conductive, although methods for machining insulating ceramics with EDM have been proposed. * EDM can cut intricate co ntours or cavities in hardened steel without the need for heat interposition to soften and re-harden them. This method can be used with any other metal or metal alloy such as titanium, hastelloy, kovar, and inconel. EDM Working dogma * It is a process of metal removal based on the principle of material removal by an interrupted electric spark discharge between the electrode tool and the work piece. * In EDM, a potential difference is applied between the tool and workpiece. * Essential Both tool and work material are to be conductors. * The tool and work material are immersed in a dielectric medium. * largely kerosene or deionised water is used as the dielectric medium. A orifice is maintained between the tool and the workpiece. * Depending upon the applied potential difference (50 to 450 V) and the gap between the tool and workpiece, an electric field would be established. * largely the tool is connected to the negative terminal (cathode) of the generator and the workpiece is connected to positive terminal (anode). * The gritty speed electrons then impinge on the job and ions on the tool. * The kinetic energy of the electrons and ions on impact with the surface of the job and tool respectively would be converted into thermic energy or heat flux. much(prenominal) intense localized heat flux leads to utmost(a) instantaneous confined rise in temperature which would be in excess of 10,000oC. * Such localized extreme rise in temperature leads to material removal. * Material removal occurs due to instant vaporization of the material as well as due to melting. * The molten metal is not removed completely but only partially. EDM Dielectric * In EDM, material removal mainly occurs due to thermal evaporation and melting. * As thermal processing is required to be carried out in absence of oxygen so that the process can be controlled and oxidation avoided. Oxidation often leads to misfortunate surface conductivity (electrical) of the workpiece hindering furt her machining. * Hence, dielectric fluid should provide an oxygen let off machining environment. * Further it should have enough strong dielectric opposition so that it does not breakdown electrically too easily. * But at the same time, it should ionise when electrons collide with its molecule. * Moreover, during sparking it should be thermally resistant as well. * by and large kerosene and deionised water is used as dielectric fluid in EDM.Electric force out MachiningELECTRIC DISCHARGE MACHINING INTRODUCTION * Sometimes it is referred to as spark machining, * Its a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks). * Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. * One of the electrodes tool-electrode or tool or electrode. * Other electrode workpiece-electrode or workpiece. As distance between th e two electrodes is reduced, the current intensity becomes greater than the strength of the dielectric (at least in some points) causing it to break. * EDM is a machining method primarily used for hard metals or those that would be very difficult to machine with traditional techniques. * EDM typically works with materials that are electrically conductive, although methods for machining insulating ceramics with EDM have been proposed. * EDM can cut intricate contours or cavities in hardened steel without the need for heat treatment to soften and re-harden them. This method can be used with any other metal or metal alloy such as titanium, hastelloy, kovar, and inconel. EDM Working Principle * It is a process of metal removal based on the principle of material removal by an interrupted electric spark discharge between the electrode tool and the work piece. * In EDM, a potential difference is applied between the tool and workpiece. * Essential Both tool and work material are to be con ductors. * The tool and work material are immersed in a dielectric medium. * Generally kerosene or deionised water is used as the dielectric medium. A gap is maintained between the tool and the workpiece. * Depending upon the applied potential difference (50 to 450 V) and the gap between the tool and workpiece, an electric field would be established. * Generally the tool is connected to the negative terminal (cathode) of the generator and the workpiece is connected to positive terminal (anode). * The high speed electrons then impinge on the job and ions on the tool. * The kinetic energy of the electrons and ions on impact with the surface of the job and tool respectively would be converted into thermal energy or heat flux. Such intense localized heat flux leads to extreme instantaneous confined rise in temperature which would be in excess of 10,000oC. * Such localized extreme rise in temperature leads to material removal. * Material removal occurs due to instant vaporization of the material as well as due to melting. * The molten metal is not removed completely but only partially. EDM Dielectric * In EDM, material removal mainly occurs due to thermal evaporation and melting. * As thermal processing is required to be carried out in absence of oxygen so that the process can be controlled and oxidation avoided. Oxidation often leads to poor surface conductivity (electrical) of the workpiece hindering further machining. * Hence, dielectric fluid should provide an oxygen free machining environment. * Further it should have enough strong dielectric resistance so that it does not breakdown electrically too easily. * But at the same time, it should ionize when electrons collide with its molecule. * Moreover, during sparking it should be thermally resistant as well. * Generally kerosene and deionised water is used as dielectric fluid in EDM.