# Principles and Characteristics of Different EDM Processes in Machining Tool and Die Steels
## 7 Future Research Directions  
Even though a high amount of work in the field of EDM was conducted, there are challenges left which still require more research, and these are listed below. * Optimizing Process Parameters: The EDM process has a multifarious nature due to the complex discharge mechanisms, which hinders its optimization. Additionally, the introduction of new materials constantly complicates the optimization of parameters. Even in TS, many grades are introduced frequently; thus, more studies are required. \begin{table}
\begin{tabular}{p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt}} \hline \hline  & **Discharge** & **Pulse-On Time** & **Pulse-Off Time** & **Voltage** & **Electrode Rotation** \\ \hline
**MRR** & **1** & **2** & **1** & **2** \\ \hline
**EWR** & **2** & **3** & **4** & **4** \\ \hline \hline \end{tabular}
\end{table} 
Table 4: General effect of major operating parameters on key performance measures. * Extending to a Wide Range of Workpiece Materials: EDM is primarily used for conductive materials; however, the current trend is to investigate the potential of EDM for machining non-conductive or semi-conductive materials, such as ceramics. * Powder-Mix EDM: Powders of different materials are mixed with dielectrics to improve the machining process. This is another area which requires further attention. Researchers need to pay more attention to the machining of different tool steel grades in different EDM types under dielectric fluids with different material powders. There is a lack of studies covering this point. * Use of Different Electrodes: Investigators can examine the performance of the EDM process by using various electrode materials, shapes, sizes, and geometries. The use of tubular electrodes is in the initial stages, and it requires further attention to deliver promising results. * Hybrid or Assisted EDM: The EDM process hybridized with some other processes provides better results. Magnetic force-assisted EDM, laser with EDM, etc. are becoming commonly used methods to overcome process limitations. The great improvement in the performance revealed in the reviewed research was related to EDM with ultrasonic action. Research trends may be directed toward the combination of these two processes. * Electrode Cooling Methods: The electrode cooling mechanism represents another field of research. The cryogenic cooling of electrodes provided positive results in terms of a reduction in TWR. * Electrical Discharge Turning (EDT) and Dry EDM: EDT is a very new concept and it requires more research. Dry EDM is also gaining interest in the research community. * Miniaturization: More efforts are needed to extend the limits of miniaturization in micro-EDM. A smaller level of electric discharge energy is needed to overcome this limitation. Furthermore, new techniques to avoid the distortion of micro-workpieces are necessary in future research. * Figure 17 shows a pictographic depiction of the future research directions. Figure 17: Future research areas in the EDM field. * The research directions can be categorized into four broad classes, which can be further allocated into sub-groups, as shown in Figure 18.  
**Author Contributions:** Conceptualization, J.E.A.Q. ; methodology, J.E.A.Q. and M.H.A. ; software, J.E.A.Q. ; validation, J.E.A.Q., A.Z. and M.H.A. ; formal analysis, J.E.A.Q. ; investigation, J.E.A.Q., A.E. and A-H.I.M. ; resources, J.E.A.Q. ; data curation, J.E.A.Q., A.E. and A.Z. ; writing--original draft preparation, J.E.A.Q. ; writing--review and editing, J.E.A.Q., A.E. and A-H.I.M. ; visualization, J.E.A.Q. and A.E. ; supervision, J.E.A.Q. ; project administration, J.E.A.Q. ; funding acquisition, J.E.A.Q. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the Research Affairs Office at UAE University, grant number 31N396. **Conflicts of Interest:** The authors declare no conflicts of interest. **Abbreviations**