# 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
#### 3.1.4 Analysis of Tool Wear Ratio
It was observed that, with increased arrays of electrodes, the carbon deposition per electrode leg gradually decreased, in general, except for the 5 \(\times\) 4 array, which has slightly higher carbon accumulation than the 4 \(\times\) 4 array. For a constant electrode leg height of 0.2\(\arcsec\), the average carbon deposition per leg is 0.6993, 0.3875, 0.3142, 0.1744, 0.1945, and 0.0779 gm for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays, respectively. In Figure 17 and Table 10, the amount of carbon deposition is shown for electrode legs with a height of 0.3\({}^{\prime\prime}\). It has been shown that, with increased arrays of electrodes, the carbon deposition per electrode leg gradually decreased for an electrode leg height of 0.3\({}^{\prime\prime}\) in general. For both cases of electrode heights (0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\)), the carbon deposition per electrode leg exhibited the same pattern. The average carbon accumulation per leg is 0.725, 0.4013, 0.2633, 0.1713, 0.1855, and 0.0717 gm for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays, respectively, for an electrode leg height of 0.3\({}^{\prime\prime}\). Figure 16: Carbon accumulation per leg with arrays of electrodes for the height of 0.2\({}^{\prime\prime}\). Figure 15: Carbon accumulation on the surface of the graphite electrode for arrays of (**a**) \(1\times 4\), (**b**) \(2\times 4\) (**c**) \(3\times 4\), (**d**) \(4\times 4\), (**e**) \(5\times 4\), and (**f**) \(6\times 4\) electrodes of height 0.2\({}^{\prime\prime}\). In die-sinking EDM, the velocity of the dielectric fluid is crucial for minimizing the carbon deposition on the tool electrode during the machining process. It has been observed that a lower dielectric fluid velocity results in a higher carbon deposition [42]. As discussed earlier, the flushing conditions improve as the electrode arrays are increased for both cases of electrode leg heights, as the dielectric fluid velocity at the channels within the electrode arrays is higher. Because of this, for both electrode leg heights, higher electrode arrays resulted in less carbon accumulation than for lower arrays. It can also be claimed that because lower arrays of electrodes accumulate more carbon than higher arrays of electrodes, the machining time is higher in the lower arrays. In addition, the higher accumulation of \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Average Weight of** & **Average Weight of** & **Average Carbon** \\
**Arrays of Electrode** & **Electrode Before** & **Electrode After** & **Accumulation per** \\  & **Machining (gm)** & **Machining (gm)** & **Leg (gm)** \\ \hline
1 \(\times\) 4 & 49.24 & 52.14 & 0.7250 \\
2 \(\times\) 4 & 50.02 & 53.23 & 0.4013 \\
3 \(\times\) 4 & 51.86 & 55.02 & 0.2633 \\
4 \(\times\) 4 & 50.52 & 53.26 & 0.1713 \\
5 \(\times\) 4 & 68.92 & 72.63 & 0.1855 \\
6 \(\times\) 4 & 94.32 & 96.04 & 0.0717 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Carbon accumulation per electrode leg for different arrays of height 0.3\({}^{\prime\prime}\). Figure 17: Carbon accumulation per leg with arrays of electrodes for the height of 0.3\({}^{\prime\prime}\). carbon at the electrode legs of lower arrays causes secondary sparking at the exit during machining, causing chipped exit edges of machined features.