Machining error induced by electrode wear is generally disregarded in conventional macro-EDM. However, electrode wear in micro-EDM significantly affects the machining accuracy of fabricated micro-features. Researchers investigated electrode wear mechanism and compensation approaches to overcome this issue. Pham et al. [
53] investigated the influence of different sources of errors, including machine, electrode dressing, electrode wear, and fixture, on the machining accuracy of micro-EDM milling; they found that electrode wear compensation was critical to achieving highly accurate micro-features. They also proposed a micro-EDM milling approach that did not rely on complex mathematical calculations. This approach is shown in Fig. 5 [
53]. As shown in Fig. 5, cavity volume is only partially completed after the first milling passes through Path 1 [
53] because electrode wear primarily appears on the edge and face of the tool.
Zcontact, which denotes the point where the electrode tip comes in contact with the workpiece, is reset. The paths for the next milling passes are then designed (Paths 2 and 3). If electrode wear is small or negligible (after Path 4 in Fig. 5), a newly dressed electrode is employed to conduct finishing milling passes. In addition, Pham et al. [
57,
58] also investigated the influence of different factors that contribute to electrode wear in micro-EDM drilling with micro-rod and micro-tube electrodes. They discussed possible methods for wear compensation and calculated electrode wear ratios using a simple method. This method is based on geometrical variations during machining. Dimov et al. [
59] presented a new tool-path generating method for layer-based micro-EDM milling. This method integrates uniform wear method and adaptive slicing to compensate for electrode wear by varying layer thickness. Complex three-dimensional cavities were fabricated by micro-EDM milling using simple-shaped electrodes. Tasi and Masuzawa [
60] studied the influence of thermal properties on the electrode wear of various materials in micro-EDM. They found that the boiling point of an electrode material played a significant role in electrode wear. Motivated by this finding, they proposed an index based on boiling phenomenon to evaluate the erosion property of electrode material. To reduce electrode wear, Uhlmann and Roehner [
61] applied novel electrode materials to fabricate tool electrodes; these materials include boron doped CVD-diamond (B-CVD) and polycrystalline diamond (PCD). They investigated the performance of B-CVD and PCD and the effect of electrode materials on tool wear and workpiece surface quality. However, further investigation must be conducted on the effects of micro-feature and element concentration in PCD and B-CVD on material removal and wear mechanism for industrial applications. Aligiri et al. [
62] employed an electro-thermal model to estimate material removal volume in real time during micro-EDM drilling; in this study, the compensation length of electrode wear was determined by comparing the estimated material removal volume with the targeted material removal volume. Bissacco et al. [
63] also proposed a new electrode wear compensation method for micro-EDM milling based on discharge counting and discharge population characterization. They found that electrode wear can be effectively compensated based on discharge counting without implementing a pulse discrimination system.