Programming for Machining in Electrical Discharge Machine: A Non-Conventional Machining Technique

Introduction

Electric discharge machining (EDM) is the most commonly used and versatile non-traditional technique (technique having no physical interaction between the tool and the workpiece) of cutting conducting metals and alloys using the heat of the electric spark from an electrode tool in presence of a flow of di-electric fluid (Bleys, P et al, 2002). It is basically an electro thermal process where the metal is melted and vaporized employing electric spark discharges at regular intervals (recurring) on the surfaces of both the electrode and the workpiece, producing a metal erosion effect (Abbas et al., 2007). The electric spark is generated due to voltage difference across the tool surface and the workpiece applied externally from the supply. EDM is extensively employed in industries such as automobile, aerospace, communication, biotechnology, and manufacturing in cutting high precision products of conducting materials such as graphite, ceramics, metals and alloys (Adrian Iosub et al,2010). An important aspect of EDM is its ability to melt and machine even hard and brittle material with ease considering the metal is electrically conductive (Vikas, Roy, A. K. et al, (2013). The components in an EDM process is shown schematically in Figure 1.

Figure 1.

Schematic diagram of Electrical discharge machining

Though EDM machining technique was first discovered in 1770 by an English scientist, it was not fully developed and precise until 1943 when Russian scientists independently learned the effect of an electric spark on the erosion of a work material which can be controlled and utilized for machining purposes. Wire EDM was developed for commercial use in around mid-1970’s which tremendously benefitted the metal cutting industries and is continuing to evolve till the present time. The implementation of EDM as machine tools in industries has made it a widely used, reliable and appealing over other traditional methods in machining.

Non-traditional techniques of machining employ non – conventional energy sources like electrical, ions and electrons, chemical, water pressure, sound, light and even indirect mechanical interactions which eliminate the risk of frictional tool wear due to direct metal contact and interactions and higher power consumptions. With the rapid rise in industrial technological growth and development and with introduction of new exotic materials (Zhou, M. And Han, F., 2009) such as engineered metallic materials, composite, high tech ceramics possessing high hardness, strength to weight ratio and heat resistance qualities (Debroy, A. & Chakraborty, S., 2013), it has become necessary to machine these materials with higher precision, accuracy and surface finish in industries like aerospace and nuclear energy (Liao, Y. S. et al, 2005). Complex shapes and sizes of products and structures can be machined suitably using the non-traditional techniques of machining with sufficient material removal rate which is improving as new advancement been made in past few years, thus yielding enhanced effectiveness, efficiency and active use of non- traditional techniques.

Tools and dies that are heat treated, super alloys, carbides, heat resistant steels, ceramics, and composites are now commonly used materials that are machined using EDM process and replacing the traditional approaches of drilling, milling, machining and grinding. The presence and importance of EDM technique has also been appreciated and felt in different other fields such as medical and surgical, optical, automotive R and D, sports, instrumentation, etc and is now considered the fourth most popular technique in machining next to milling, turning and grinding. The cutting speeds of today’s EDM had dramatically increased which served as a major advantage in gaining attention from the public. The actual EDM machine has been shown in Figures 2 and 3.

Figure 2.

Electrical discharge machine

Figure 3.

Electrical discharge machine Programme unit