# 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)  
The influence of different arrays and heights of electrode legs on the material removal rate and machining time for machined features on silicon has been investigated. Figure 5a,b show the average machining time of through-hole machining on silicon workpieces for each entire array of electrode legs of heights of 0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\). The machining time for 1 \(\times\) 4 (4 legs), 2 \(\times\) 4 (8 legs), 3 \(\times\) 4 (12 legs), 4 \(\times\) 4 (16 legs), 5 \(\times\) 4 (20 legs), and 6 \(\times\) 4 (24 legs) arrays were 131.416, 58.383, 41.4, 38.949, 45.310, and 45.078 min, respectively, for electrode legs of height 0.2\({}^{\prime\prime}\), and 166.045, 94.167,41.917, 39.392, 46.550, and 48.16 min, respectively, for electrode legs of height 0.3\({}^{\prime\prime}\). It can be said that for both heights (0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\)), the time required for machining 6 \(\times\) 4 arrays (24 legs) was shorter compared to 1 \(\times\) 4 arrays (4 legs). It would be quite unfair to compare the machining time with different arrays of electrode  
Figure 4: Measurement and characterization of electrode legs. (**a**) Dimension of electrode legs, (**b**) different electrode heights, (**c**) markings of legs; (**d**) electrode under an optical microscope, (**e**) measurement of length and breadth, (**f**) length between legs, (**g**) breadth between legs, (**h**) height of electrode legs, and (**i**) ruler at the same magnification of 6.25\(\times\). [In (**a**), green color arrow indicates electrode leg width, blue color arrow indicates electrode leg breadth, red color arrow indicates column channel width, and yellow color arrow indicates row channel width; In (**b**), yellow color arrow indicates electrode leg height). legs rather than comparing the machining time for a single feature on silicon or machining time per electrode leg. The time required for machining a single feature in silicon using each electrode leg for different arrays and heights was investigated while keeping the EDM process parameters unchanged. Figure 6 represents the average time required per through hole for machining silicon using arrays of electrodes with two different leg heights of 0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\). For machining a single feature or through slots in silicon using electrode arrays with a 0.2\({}^{\prime\prime}\) leg height, the machining times have been calculated as 32.854 min, 7.298 min, 3.45 min, 2.434 min, 2.266 min, and 1.878 min for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays, respectively. There is a drastic improvement in reducing the machining time per square feature/hole on silicon with the increased number of arrays of electrode legs, demonstrating the effective mass fabrication of square features on silicon using the proposed electrode design strategy. This will allow users to use arrays of electrodes rather than a traditional method of single electrodes when a large number of features are required. On the other hand, the average machining times required per through hole for the electrode leg height of 0.3\({}^{\prime\prime}\) have been calculated as 41.511 min, 11.771 min, 3.493 min, 2.462 min, 2.327 min, and 3.45 min for 1 \(\times\) 4, 2 \(\times\) 4, 3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4 arrays, respectively. It is found that with variation in arrays, it takes significantly less time to machine unit through holes for 6 \(\times\) 4 arrays compared to 1 \(\times\) 4 arrays, which can be observed for both cases of leg heights. Figure 5: Average machining time for through holes of 4, 8, 12, 16, 20, and 24 electrode legs of (**a**) electrode legs of height 0.2\({}^{\prime\prime}\), and (**b**) electrode legs of height 0.3\({}^{\prime\prime}\).