Improper flushing of dielectric fluid adversely affects the dimensional accuracy produced in EDM deep hole process. This paper investigates the dimensional accuracy (e.g. roundness error and gap clearance) in EDM deep hole process of AISI P20 tool steel. The inner flushing electrode is newly proposed in this study, using the multi-hole interior flushing technique coupled with electrode rotation. The results showed that the multi-hole interior flushing with electrode rotation improves the deviation of roundness error due to improved flushing. In addition, using multi-hole interior flushing with electrode rotation provides the cylindrical shape in gap clearance. Finally, a more powerful flushing technique is achieved with newly purposed multi-hole interior flushing technique on roundness error and gap clearance, respectively.

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This research investigates the effect of machining parameters on material removal rate, electrode wear ratio, and gap clearance of macro deep holes with a depth-to-diameter ratio over four. The experiments were carried out using electrical discharge machining with side flushing and multi-aperture flushing to improve the machining performance and surface integrity. The machining parameters were pulse on-time, pulse off-time, current, and electrode rotation. Response surface methodology and the desirability function were used to optimize the electrical discharge machining parameters. The results showed that pulse on-time, current, and electrode rotation were positively correlated with the material removal rate. The electrode wear ratio was inversely correlated with pulse on-time and electrode rotation but positively correlated with current. Gap clearance was positively correlated with pulse on-time but inversely correlated with pulse off-time, current, and electrode rotation. The optimal machining condition of electrical discharge machining with side flushing was 100 µs pulse on-time, 20 µs pulse off-time, 15 A current, and 70 rpm electrode rotation; and that of electrical discharge machining with multi-aperture flushing was 130 µs, 2 µs, 15 A, and 70 rpm. The novelty of this research lies in the use of multi-aperture flushing to improve the machining performance, enable a more uniform GC profile, and minimize the incidence of recast layer.

In this study, experiments were performed to study the effects of electrode materials mixed with nickel in electrical discharge machining (EDM) of SUS 304 material. Experiments were constructed using parameters consisting of pulse-on time, pulse-off time, discharge current and electrode polarity, respectively. The analysis of structural features of the surface was accomplished using a scanning electron microscope (SEM) as well as an element analysis created on the surface, after the EDM process, by using Energy-dispersive x-ray spectroscopy (EDS). The results of the experiments found that nickel elements in the electrode material have an effect on the working performance of material removal rate and electrode wear ratio. The electrode wear ratio reduces when nickel elements increase. Moreover, the surface roughness had the lowest level at electrode 15 % nickel element. Thus, electrode wear during the EDM process of nickel element from electrodes and other elements, combined with surface metalworking, becomes a recast layer of nickel.