History Of Electrical Discharge Machining

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CHAPTER 1

INTRODUCTION

1.1 ELECTRICAL DISCHARGE MACHINING (EDM)

The phenomenon of erosion of metals by electric spark was first noticed by Joseph Priestily in 1878 but this was not used for machining of metals until 1930s. Controlled machining of metals by electric sparks was first done by Lazarenko in Russia in 1944 [2].

One of the most widely used Non-Conventional Machining process in industry is Electrical Discharge Machining (EDM). Electric Discharge Machining is a non- traditional concept which is based on the principle of removing material by means of repeated electrical discharges between the tool termed as electrode and the work piece in the presence of a dielectric fluid [3]. Electrical Discharge Machining (EDM) uses thermal energy to achieve a high-precision metal removal process from a fine, accurately controlled electrical discharge. The electrode is moved towards the work piece until the gap is small enough so that the impressed voltage is great enough to ionize the dielectric [1]. Short duration discharges are generated in a liquid dielectric gap, which separates tool and work piece. The material is removed with the erosive effect of the electrical discharges from tool and work piece. EDM does not make direct contact between the electrode and the work piece thus it can eliminate mechanical stresses, chatter and vibration problems during machining [3, 4].

EDM is commonly used for machining very hard and tough materials such as tool steels and carbides and for finishing parts for aerospace, automotive industry and surgical components. It is also used to produce complex shapes and small diameter holes, which are difficult or impossible to machine using conventional methods. Since EDM uses an electric discharge ...

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...essing because of the abilities to provide accurate, cost-effective and flexible products.

1.4.1 Advantages of WEDM Process:

• As continuously travelling wire is used as the negative electrode, so electrode fabrication is not required as in EDM.
• There is no direct contact between the work piece and the wire, eliminating the mechanical stresses during machining.
• WEDM process can be applied to all electrically conducting metals and alloys irrespective of their melting points, hardness, toughness or brittleness.
• Users can run their work pieces over night or over the weekend unattended.

1.4.2 Disadvantages of WEDM Process:

• High capital cost is required for WEDM process

• There is a problem regarding the formation of recast layer

• WEDM process exhibits very slow cutting rate

• It is not applicable to very large work piece

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