# Effectiveness of Electrode Design Methodologies for Fast EDM Slotting of Thick Silicon Wafers
## 4 Conclusions  
This study proposes two electrode design methodologies for improving machining speed during the slotting of silicon using die-sinking EDM. The influence of arrays of electrodes and electrode leg heights, as well as the effect of solid vs. hollow electrodes with different wall thicknesses on the material removal rate, tool wear rate, dimensional accuracy, and edge surface quality of the machined features on silicon workpieces have been investigated. For the tool wear rate, carbon deposition on the surface of the tool electrode resulted in a negative tool wear rate compared to most of the studies where a positive tool wear rate was reported because of the removal of material from the tool electrode. The effect of carbon deposition on the EDM performance has also been investigated. The conclusions that can be drawn from this experimental study are as follows:  
* The increased arrays of electrode legs have a positive effect on the machining time and material removal rate. With the increment in arrays of the electrode, the machining time required for each slot decreased and the material removal rate per slot increased, irrespective of the height of the electrode leg. For both cases of electrode leg heights (0.2\({}^{\prime\prime}\) and 0.3\({}^{\prime\prime}\)), 6 \(\times\) 4 arrays of electrodes required less time per slot and provided a higher material removal rate than the 5 \(\times\) 4, 4 \(\times\) 4, 3 \(\times\) 4, 2 \(\times\) 4, and 1 \(\times\) 4 arrays of electrodes;
* For 1 \(\times\) 4 and 2 \(\times\) 4 arrays of electrodes, smaller electrode leg heights performed better in terms of the MRR or machining time. For the case of higher arrays of electrodes (3 \(\times\) 4, 4 \(\times\) 4, 5 \(\times\) 4, and 6 \(\times\) 4) there are no significant differences in the MRR for different electrode leg heights. It is found that with increased arrays of electrodes, the effect of the electrode's leg height became insignificant;  
Figure 24: Carbon accumulation on the face of block electrode and hollow electrodes with different wall thicknesses. * The overall quality of the machined features on the silicon workpiece became better with an increased array of electrodes due to improvements in the flushing conditions. The mirror image of the graphite electrode on the silicon workpiece for 6 \(\times\) 4 arrays of electrodes is closer to the desired output than those of 5 \(\times\) 4, 4 \(\times\) 4, 3 \(\times\) 4, 2 \(\times\) 4, and 1 \(\times\) 4 arrays of electrodes. For both heights, the overall quality of the features of the mirror image of the graphite electrode leg on the workpiece is nearly comparable;
* For both cases of electrode leg heights, carbon deposition per electrode has gradually decreased as the arrays of electrodes have increased. Carbon deposition per electrode leg is quite similar for different arrays of electrodes for both electrode heights. Carbon deposition also plays a critical role in determining the material removal rate and edge quality of the machined features. The higher the accumulation of carbon, the higher the chance of secondary sparking, thus resulting in chipping and zagged edges of machined features on silicon;
* Careful electrode array design, considering the flow direction of dielectric fluid and selecting an ideal number of channels in between electrode arrays and leg heights of the electrodes, can increase both the machining speed (i.e., productivity) and feature quality (i.e., dimensional accuracy, quality of the machined parts, and edge surface finish) of the machined features on silicon via die-sinking EDM;
* The hollow electrodes can provide a faster machining speed compared to fully solid block electrodes when machining the same through features on silicon. With the decrement in the wall thickness of the hollow electrode, there is an increase in the value of the MRR and a reduction in the required machining time to complete a slot.