# Effectiveness of Electrode Design Methodologies for Fast EDM Slotting of Thick Silicon Wafers
## 3 Results and Discussion
### Effect of Electrode Arrays on Machining Speed with Varied Electrode Leg Heights
#### 3.1.3 Analysis of Quality of the Machined Features on Silicon
create smaller cross-sectional area channels compared to 0.3\({}^{\prime\prime}\) electrode legs at a fixed flow rate, this results in a higher velocity at the channels of the 0.2\({}^{\prime\prime}\) electrode legs. Increased flushing velocity at the channels enhances the flushing conditions by effectively eliminating debris from the workpiece. However, because of the predominance of the electrode's jump action, this (1 st) effect becomes less significant with more electrode arrays. Because of this, the MRR for higher arrays of electrode (3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4) legs is relatively comparable for both heights of electrode legs. Using the Olympus SZX-12 optical microscope, [PERSON], Tokyo, Japan and Image Pro Plus 7 software, (version 7), Media Cybernetics, Stoneham, MA, USA, the characteristics of the graphite electrode (length and width) and the workpiece at the entry and exit sides (length and width) were determined. The characterization of Sample-1 for 1 \(\times\) 4, 2 \(\times\) 4, and 3 \(\times\) 4; Sample-2 for 4 \(\times\) 4; and Sample-3 for 5 \(\times\) 4 and 6 \(\times\) 4 arrays of electrodes comprising 4, 8, 12, 16, 20, and 24 electrode legs, respectively, for heights of 0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\) are listed in Tables 6 and 7. This also shows that the dimensions of machined square features are higher than the dimensions of the electrodes used to machine them, due to the spark gap around the electrode. As the machining parameters are kept constant, the spark gap should be constant as well, and hence, the variations in the dimensions of machined features are associated with the effectiveness of the flushing conditions. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{\ \begin{tabular}{c} **Number** \\ **of Electrode** \\ **Legs** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Marking of** \\ **Legs** \\ \end{tabular}  } & \multicolumn{2}{c}{**Electrode**} & \multicolumn{2}{c}{**Workpiece**} & \multicolumn{2}{c}{**Workpiece (Exit)**} \\ \cline{3-8}  & & & **Length** & **Width** & **Length** & **Width** & **Length** & **Width** \\  & & **(\(\mathbf{\mu}\)m)** & **(\(\mathbf{\mu}\)m)** & **(\(\mathbf{\mu}\)m)** & **(\(\mathbf{\mu}\)m)** & **(\(\mathbf{\mu}\)m)** & **(\(\mathbf{\mu}\)m)** & **(\(\mathbf{\mu}\)m)** \\ \hline \multirow{4}{*}{4 (1 \(\times\) 4)} & Leg-1  
The entry and exit sides of Sample-1 (height 0.2\({}^{\prime\prime}\) of Leg-1) for 1 \(\times\) 4, 2 \(\times\) 4, and 3 \(\times\) 4 arrays of the electrode are shown in Figure 12. It can be seen from the images that the exits are more damaged than the entry sides, as shown in Figure 12. This pattern occurs because during the machining of the entry side, the surface of the graphite electrode was not worn out or the carbon accumulation was very little. Nevertheless, when cutting into the workpiece's exit side, there is a significant buildup of carbon on the graphite electrode surface, which creates unwanted sparks and causes damage at the edges of the machined features on the silicon workpiece. The percentage deviations of machined features on the silicon workpiece for the electrode length and width for various arrays and varied heights (0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\)) were compared. The overall percentages of deviation for the heights of 0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\) have also been compared. From Table 8 and Figures 13 and 14, it can be seen that the average percentage of deviation in the case of the width and length decreases with the increased number of arrays. The average percentages of deviation (%) for the width are 10.42, 9.61, 8.06, 7.04, 6.38, and 5.81 for the electrode height 0.2\({}^{\prime\prime}\) and 10.65, 8.47, 8.22, 7.21, 6.76, and 6.41 for the electrode height 0.3\({}^{\prime\prime}\), for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 electrode  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{\