# 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
#### 3.1.2 Analysis of Machining Time and Material Removal Rate (MRR)
From Figure 6, it is observed that when it comes to productivity or cutting down the amount of time required to machine each through hole in each array of electrode legs, smaller heights perform better than bigger heights. For 1 \(\times\) 4 arrays, the machining time for each through hole is 32.85 and 41.51 min for heights 0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\), respectively. Similarly, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays of electrode legs show the same trend. Another significant takeaway is that the influence of the leg height is only significant for smaller arrays of electrodes (1 \(\times\) 4 and 2 \(\times\) 4). With the increased arrays of electrodes, both heights of electrodes perform quite similarly. For machining a unit through hole with a height of 0.2\({}^{\prime\prime}\) as opposed to 0.3\({}^{\prime\prime}\), less time is required. When a smaller leg (0.2\({}^{\prime\prime}\)) is utilized in the electrode arrays, the machining time per through hole is decreased by 8.66, 4.47, 0.04, 0.043, 0.061, and 0.129 min for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays of electrode legs, respectively, compared to bigger legs (0.3\({}^{\prime\prime}\)). It is worth mentioning that the machining time for slotting silicon for the smaller height (0.2\({}^{\prime\prime}\)) is more consistent than for the bigger height (0.3\({}^{\prime\prime}\)) of electrode legs. Because of this, we have selected the 0.2\({}^{\prime\prime}\) depth for hollow electrodes with different thicknesses for our study. Figure 7 presents the variation in the MRR for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays of electrodes with two electrode leg heights of 0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\). It can be observed that there is an increase in the MRR with the increment in arrays of electrode legs for both leg heights of 0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\). The values of the MRR are 2.003, 7.986, 16.691, 23.463, 25.313, and 30.499 mm\({}^{3}\)/min for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays of electrodes, respectively, for an electrode leg height of 0.2\({}^{\prime\prime}\). In the case of 6 \(\times\) 4 arrays, the MRR is around 15 times more than for 1 \(\times\) 4 arrays, approximately 4 times more than for 2 \(\times\) 4 arrays, and around 2 times more than for 3 \(\times\) 4 arrays of electrode legs. The same trend can also be seen in the case of the electrode leg height of 0.3\({}^{\prime\prime}\), where with the increased arrays of the electrode, there is an increment in the MRR. The values of the MRR are found to be 1.643, 5.180, 16.245, 23.016, 24.433, and 28.390 mm\({}^{3}\)/min for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays of electrodes, respectively, for the electrode leg height of 0.3\({}^{\prime\prime}\). It is clear from comparing these findings side by side, as shown in Figure 7, that a smaller electrode height performs better than bigger height in terms of productivity or the material removal rate in general, but that the performance gap is not that significant. Figure 6: Variation in time required for machining each through hole for electrode heights of 0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\).