# Principles and Characteristics of Different EDM Processes in Machining Tool and Die Steels
## 4 Research in EDM of Tool Steel
### Performance Measures in EDM of Tool Steels
The study analyzed the constituents of aerosol generated from the process, studied the morphology of the particulates, and suggested the control measures to reduce the risk of aerosol exposure. The authors reported that the composition of generated aerosol depends on the composition of the electrode materials and on the boiling point of its constituents. It was found that 69% of the aerosol consists of metallic particles and 12.2% consists of the hydrocarbons attached to it. The remaining portion of the aerosols consisted of carbon dust and unidentified compounds. The particle size of the aerosol was observed in the range of 25-29 nm with spherical shape. In another study [194], a combination of Taguchi and fuzzy TOPSIS (technique for order preference by simulation of ideal solution) methods was used to solve multi-response parameter optimization problems for the EDM process in a green manufacturing environment. The study developed a decision-making model to select the process parameters that achieved green EDM. A Taguchi L9 orthogonal array was utilized to analyze the sensitivity of green manufacturing attributes regarding different process parameters including peak current, pulse duration, dielectric level, and flushing pressure. Triangular fuzzy numbers were used to obtain weighing factors for the output responses, and the most suitable combinations of parameters were selected based on the TOPSIS technique. The authors reported that the optimal machining performance for green EDM was 4.5 A peak current, 261 \(\upmu\)m pulse duration, 40 mm dielectric level, and 0.5 kg/cm\({}^{2}\) flushing pressure. They also identified that the peak current was the most influential parameter in multi-performance characteristics. Furthermore, an investigation presented [193] the application of Taguchi's robust design to find the optimal machining process parameters of the EDM process of precise cylindrical forms on high-speed steel. The study considered six design factors, namely, intensity supplied by the generator of the EDM machine, pulse-on time, voltage, pulse-off time, servo, and rotational speed, and it evaluated their effect on the MRR. The authors reported that the most important factors affecting the cost-effectiveness were intensity, spindle speed, servo, and pulse-on time. It was found that the actual gain of 0.023 for MRR was very close to the predicted value of 0.021. Fuzzy logic was also considered to study the influence of processes parameters on the performance parameters; for example, in one study [121], an adaptive neuro-fuzzy inference system model was developed to predict the white layer thickness and average SR achieved as a function of the process parameters. Pulse duration, open-circuit voltage, dielectric flushing pressure, and wire feed rate were taken as the model's input features. The model combined the modeling function of fuzzy inference with the learning ability of artificial neural networks (ANN). User-friendly fuzzy-expert systems to select the EDM parameters were also developed [188]. Furthermore, [PERSON] and [PERSON] [154] applied the integration of fuzzy logic analysis with Taguchi methods to optimize the accuracy of the high-speed EDM process. [PERSON] et al. [186] presented statistical analysis of electrode wear in the EDM of tool steel DIN 1.2714 used in forging dies. Moreover, in another study, [PERSON] et al. [202] utilized the finite element method to conduct thermo-analysis on material removal in the finish cut of wire EDM to study the influence of the discharge current on machining surfaces. The authors reported that the long-duration pulses could not meet the machining requirements during finish machining that had high requirements in SR, and only short-duration pulses could be used to carry out the machining. Figure 4 shows the surface morphologies of long- and short-duration pulses, and Figure 5 shows the SEM microphotographs of single craters under the two pulse durations.