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Top1. Introduction
Non-conventional machining processes are the requirements of the fastest growing industries because of the precision, complex, intricate shape of the work material, higher tolerances and economically. Hard materials and super alloys such as titanium alloys, tungsten carbides, high carbon tool steels generally used in tool industries, automotive and electronics industries, medical and aerospace are very difficult–to-machine by conventional manufacturing processes. Therefore, the ease of material cutting and machining non-conventional machining is preferred. WEDM is generally used to produce complex shapes die cavities and forming tools, fixtures, gauges, etc. which are difficult to produce by means of any other conventional and non-conventional machining methods except micro-machining (Sommer & Sommer, 2016).
Titanium alloys (Ti-alloys) are mostly utilized in aerospace and automotive industries to manufacture higher precision components. Ti-6Al-4V grade 5 titanium alloy is used for the manufacturing of diesel engine components such as connecting rods, gas turbine parts, intake valves, etc. and this alloy covers the 50% of total global consumption (Veiga, 2012).
WEDM is a variation and development of EDM. In 1969, the Swiss firm Agie developed and delivered the world’s initially WEDM machine. These machines had machining ability to cut the material about 21 mm2/min. per hour. These machines were extremely slow in production rate. After the continuous improvements in the machining ability, the machining speed improved. WEDM removes material from the work metal with the use of electricity by means of spark erosion as shown in Figure 1. It is most important requirement that the work material should be electrically conductive. AC serve motors are exploited to provide positioning, stability and enhancement of wire tension. A DC or AC servo mechanism maintains the gap (0.051 to 0.076 mm) between the electrode and the work material. This maintained gap prevents the short circuiting of wire.
Figure 1. Working principle of WEDM
‘Dielectric’ is the shield between the wire electrode and material. De-ionized water is generally used as a dielectric medium because the dielectric medium acts as an insulator. In this process, the material is submerged in the dielectric medium. When the voltage is applied, the electric pulses are generated, fluid ionizes and a spark generates between the electrode wire and work material, the controlled spark precisely erodes the metal from the work material causing it to melt and vaporize. Pressurized dielectric fluid flows continuously. It cools the vaporize material and carry away the particles from the cutting section. The dielectric passes through the filter to remove suspended particles and it is used continuously. Chillers are used to maintain the temperature of dielectric fluids for higher machining efficiency and accuracy. In WEDM the wire electrode never comes in contact with the work piece, therefore this process is stress free cutting operation (Sommer & Sommer, 2013; Kumar & Subramani, 2018; Anwar et al., 2017; Miller et al., 2004).