Electrical Discharge Machining (Edm)
Chapter 1
Electrical discharge machining (EDM)
1.1 Introduction:
Electrical discharge machining (EDM) is one of the most extensively used non-conventional material removal processes. Its unique feature of using thermal energy to machine electrically conductive parts regardless of hardness has been its distinctive advantage in the manufacture of mould, die, automotive, aerospace and surgical components. In addition, EDM does not make direct contact between the electrode and the workpiece eliminating mechanical stresses, chatter and vibration problems during machining.
1.2 EDM operation:
The principle of EDM is based on the erosion of metals by spark discharge. The basic EDM system consists of shaped tool (electrode) and workpiece connected to a dc power supply and placed in dielectric fluid. When potential difference between tool and workpiece is sufficiently high a transient spark discharges through fluid removing small amount of metal from workpiece. The thermal energy generates a channel of plasma between the cathode and anode at a temperature in the range of 8000 to 12,000 °C or as high as 20,000 °C initializing a substantial amount of heating and melting of material at the surface of each pole. When the pulsating direct current supply occurring at the rate of approximately 50 kHz to 500 kHz is turned off, the plasma channel breaks down. This causes a sudden reduction in the temperature allowing the circulating dielectric fluid to implore the plasma channel and flush the molten material from the pole surfaces in the form of microscopic debris. This process of melting and evaporating material from the workpiece surface is in complete contrast to the conventional machining processes, as chips are not mechanically produced [1,2]. The volume of material removed per discharge is typically in the range of 10-6–10-4 mm3 and the material removal rate (MRR) is usually between 2 and 400 mm3/min depending on specific application. Since the shaped electrode defines
Electrical discharge machining (EDM)
1.1 Introduction:
Electrical discharge machining (EDM) is one of the most extensively used non-conventional material removal processes. Its unique feature of using thermal energy to machine electrically conductive parts regardless of hardness has been its distinctive advantage in the manufacture of mould, die, automotive, aerospace and surgical components. In addition, EDM does not make direct contact between the electrode and the workpiece eliminating mechanical stresses, chatter and vibration problems during machining.
1.2 EDM operation:
The principle of EDM is based on the erosion of metals by spark discharge. The basic EDM system consists of shaped tool (electrode) and workpiece connected to a dc power supply and placed in dielectric fluid. When potential difference between tool and workpiece is sufficiently high a transient spark discharges through fluid removing small amount of metal from workpiece. The thermal energy generates a channel of plasma between the cathode and anode at a temperature in the range of 8000 to 12,000 °C or as high as 20,000 °C initializing a substantial amount of heating and melting of material at the surface of each pole. When the pulsating direct current supply occurring at the rate of approximately 50 kHz to 500 kHz is turned off, the plasma channel breaks down. This causes a sudden reduction in the temperature allowing the circulating dielectric fluid to implore the plasma channel and flush the molten material from the pole surfaces in the form of microscopic debris. This process of melting and evaporating material from the workpiece surface is in complete contrast to the conventional machining processes, as chips are not mechanically produced [1,2]. The volume of material removed per discharge is typically in the range of 10-6–10-4 mm3 and the material removal rate (MRR) is usually between 2 and 400 mm3/min depending on specific application. Since the shaped electrode defines
References: [3] S. Kumara, R. Singh, T.P. Singh, B.L. Sethi, Surface modification by electrical discharge machining: A review, Journal of Materials Processing Technology, (2008). [4] J. S. Soni, G. Chakraverti, Machining characteristics of titanium with rotary electro-discharge machining, Wear, 171 (1994) 51-58. [5] M. Ghoreishi, J. Atkinson, A comparative experimental study of machining characteristics in vibratory, rotary and vibro-rotary electro-discharge machining, Journal of Materials Processing Technology, 120 (2002) 374-384. [6] J. S. Soni, Microanalysis of debris formed rotary EDM of titanium alloy (Ti 6 Al 4V) and die steel (T 215 Cr12), Wear, 177 (1994) 71-79. [7] C. C. Wang, B. H. Yan, Blind-hole drilling of Al2O3/6061Al composite using rotary electro-discharge machining, J Mat Process Technol, 102 (2000) 90-102. [8] S. K. Chak, P. V. Rao, The drilling of Al2O3 using a pulsed DC supply with a rotary abrasive electrode by the electrochemical discharge process, Int J Adv Manuf Technol, (2006).