Investigation of fill factor and tool path effects on micro-EDM milling

In this paper, the influence of tool path variation on micro- EDM milling performance of square micro-cavities having three different fill factors (FF, ratio between electrode tool section area and feature section area) is presented. Three cavities for each considered FF have been machined and the experimental results have been evaluated in terms of material removal rate (MRR) and tool wear ratio (TWR). The analysis show that the machining of the cavity with medium FF displays a MRR which is unexpectedly smaller than the one measured for the smallest cavity. The reason of such results has been investigated by analyzing the influence of tool path on working conditions. Hence, a new set of micro-cavities has been machined varying the path lengths. The new results confirmed that, in dependence on the FF and cavity depth (expressed in terms of aspect ratio, AR), the proper setting of the tool path lengths can significantly improve the machining performance, in particular, in terms of MRR.