## 2 Materials and Methods
Likewise, the design type named as relief angle with land (D\({}_{\text{RL}}\)) was further characterized into five subdesigns such as D\({}_{\text{RL10}}\), D\({}_{\text{RL20}}\), D\({}_{\text{RL30}}\), D\({}_{\text{RL45}}\), and D\({}_{\text{RL190}}\). Five relief angles with a constant land thickness of 1 mm were provided. The difference between D\({}_{\text{R}}\) and D\({}_{\text{RL}}\) is the inclusion of land that was kept constant (1 mm thickness) in the case of D\({}_{\text{RL}}\). In this way, a total of 10 electrode designs were utilized to perform the machining on tungsten carbide. The detail of these designs is presented in Table 4. A schematic illustration of the designs is shown in Figure 1a and the developed electrodes are shown in Figure 1b. In each of the designs, the face diameter was 8 mm and the shank diameter was 5 mm, which were kept constant. The total height of each of the electrodes was also kept constant at 50 mm. However, due to the relief angles and land thickness, the face height and the shank height varied but the overall height of the electrode remained the same, i.e., 50 mm. The picture of these designs could be fully comprehended by pivoting Table 4 with Figure 1. Tools were prepared on the lathe using constant parametric settings (spindle speed, tool feed rate, depth of cut, etc.) and other machining conditions. For example, the high speed steel (HSS) turning tool was used to prepare copper electrodes and parameters including a spindle speed of 375 rpm, tool feed rate of \begin{table}
\begin{tabular}{c c c} \hline
**Properties** & **Values** & **Units** \\ \hline
**Density** & 15.5 & g/cm\({}^{3}\) \\
**Hardness** & 92.3 & HRA \\
**Toughness** & 50 & kg/mm\({}^{2}\) \\
**Tensile strength** & 179 & kg/mm\({}^{2}\) \\
**Compressive strength** & 410 & kg/mm\({}^{2}\) \\
**Melting Point** & 3140 & \({}^{\circ}\)C \\
**Thermal conductivity** & 0.502 & W/cm\({}^{\circ}\)C \\
**Thermal coefficient of expansion** & \(5.5\times 10^{-6}\) & K\({}^{-1}\) \\
**Specific heat** & 39.8 & J/molK \\
**Electrical Resistivity** & \(17\times 10^{-6}\) & Ohm cm \\ \hline \end{tabular}
\end{table} 
Table 2: Properties of tungsten carbide (mechanical, thermal, and electrical) [7; 8; 29]. \begin{table}
\begin{tabular}{c c c c} \hline
**Electrodes** & \begin{tabular}{c} Tool \\ Workpiece \\ \end{tabular} & \
\begin{tabular}{c} Copper \\ Tungsten carbide \\ \end{tabular} &
\begin{tabular}{c} – \\ – \\ \end{tabular} \\ \hline
**Discharge current** & 30 A & A \\ Spark Voltage & 5 V & V \\ Pulse on-time & 100 & \(\upmu\)s \\ Pulse off-time & 50 & \(\upmu\)s \\
**EDM parameters** & Electrode Polarity & Work & +ve \\  & & Tool & –ve \\  & Servo sensitivity & 3 & – \\ Spark-flushing time ratio & 1 & – \\  & Dielectric & Kerosene oil & – \\  & Flushing mode & Continuous & – \\ \hline \end{tabular}
\end{table} 
Table 3: Electrodes and electric discharge machining (EDM) parameters (constants). 0.175 mm/rev, and depth of cut was 1 mm for rough turning and 0.1 mm for finish turning. In this way, the variability in tool dimensions was minimized. For each experimental run a fresh tool was employed so that the effects of tool wear on the machining performance could also be avoided. Six performance measures were considered in order to access the effect of electrode designs during EDM of WC.