## 1 Introduction  
The requirement of improved strength-to-weight ratio materials has led to the introduction of composite materials in many applications such as structural, automotive, space, manufacturing, etc. The major challenges while switching over to composite materials from conventional metals or alloys is the machining of the material to the required size and shape. Obtaining the materials of near-net shape requires a machining process. Therefore, machining becomes necessary for the manufacturing of a part using composite materials. This leads to the use of nonconventional machining processes where the tool and workpiece will never have physical contact and the machining is carried out by using a spark or chemical process or by using a water jet. In the nonconventional machining process, recent trends have inclined towards EDM due to its cost effectiveness and the capability to handle various composites effectively. These reasons have persuaded a lot of manufacturers to opt for EDM as a machining process for hard-to-machine composite material, mainly metal matrix composites for manufacturing different components. [PERSON] and [PERSON] [1] worked on optimising the parameters of Al6061-5% Al2O3-3% SiC-2% E-glass in EDM. The work identified current and pulse-on time as the major contributors in surface roughness and MRR. It was also identified, using the Box-Behnken design of experiments of response surface methodology (RSM) that optimum current was 12.4 A, pulse-on time was 30 us and pulse-off time was 7 us. The work also identified that the addition of E-glass did not affect the properties of the material. [PERSON] and [PERSON] [2] developed an experimental analysis using the grey relation method for Al6061 reinforced with 15% SiC. The experiment was also conducted using a change of polarity of the workpiece. It was identified that the current was the significant contributor in the output parameters of MRR and surface roughness. It was also identified that the pulse-on time and the pressure of lubricant also plays a significant role in the output parameters. The identified optimal values for current, pressure of dielectric and pulse-on time were 4 A, 0.5 kg/cm2 and 400 us, respectively. The work also identified that a negative polarity of the electrode provided better results  
[PERSON] et al. [3] experimented to identify the contributing parameters for Al6061 with 10% SiC. The work concluded that the higher current increases the MRR and tool wear rate, but diminishes the surface roughness. The increase in pulse-on time increases the MRR as well as the surface roughness. The optimum values of pulse-on time and pulse-off time were identified to be in the range of 90 to 200 us for better output parameters. [PERSON], [PERSON] and [PERSON] [4] used grey relation analysis (GRA) along with the response surface methodology (RSM) approach to optimise the Al6061 cenosphere composite. It was identified that the hybrid approach is able to provide an improved result when compared with the initial experimental results. The optimum values identified were a pulse current of 9.9126 A, pulse-on time of 210.002 us, reinforcement content of 3.6936% and flushing pressure of 0.5999 MPa. [PERSON] et al. [5] worked on optimising the parameters for Al6061, Inconel and SKD11. The work identified that the percentage of energy transferred to the workpiece was small for all three materials. The range of energy transfer to the workpiece was identified to be between 8 and 12% for Al6061 and between 3 and 4% for Inconel and SKD 11. It was also identified that for difficult-to-cut materials, the increase in discharge current reduced specific discharge energy, but the energy distribution to the workpiece was found to be constant. [PERSON] et al. [6] conducted ANOVA-based analysis on Al6061 with 10% SiC. The work identified that the increase in current and pulse-on time increased the parameters considered, which were mainly MRR and surface roughness. By using RSM, the MRR was improved by 30.13% in powder-mixed EDM and 24.27% in normal EDM.