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Nowadays, additive manufacturing (AM)-based rapid prototyping (RP) is used as a convenient route for making tool electrodes required in electrical discharge machining (EDM). AM enables direct fabrication of complex shaped EDM electrode in comparatively less time in contrast to subtractive machining processes. In this study, an EDM electrode is prepared directly by selective laser sintering (SLS) process using metal matrix composite of aluminium (Al), silicon (Si) and magnesium (Mg). To study the performance of the prepared RP tool electrode in electrical discharge machining, titanium is used as workpiece material and EDM-30 oil as dielectric medium during machining. The performance of the prepared tool electrode is compared with conventional copper and graphite tool electrodes. Experiments have been conducted changing EDM process parameters viz. open circuit voltage (V), peak current (Ip), duty cycle (τ) and pulse duration (Ton) along with three tool electrodes such as RP, graphite and copper tool electrodes. The performance measures considered during the experimental study are material removal rate (MRR), tool wear rate (TWR), average surface roughness (Ra), white layer thickness (WLT), surface crack density (SCD) and micro-hardness (MH) on white layer. SEM and EDX of the machined surface reveal that tool material is generally eroded and deposited on the machined surface with formation of metal carbides. However, tool erosion is more pronounced in case of RP tool electrode. XRD analysis reveals the formation of titanium carbides on the machined surface resulting in increase in the micro-hardness of white layer. Discharge current and tool type are found to be significant parameters influencing the performance measures considered in the study. The surface produced when machined with RP tool electrode exhibits superior surface characteristics while graphite tool electrode produces better MRR and TWR. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond (PCD) is increasingly becomes an important material used in the industry for cutting tools of difficult-to-machine materials due to its excellent characteristics such as hardness, toughness and wear resistance. However, its applications are restricted because of the PCD material is difficult to machine. Therefore, electrical discharge machining (EDM) is an ideal method suitable for PCD materials due to its non-contact process nature. The performance of EDM, however, is significantly influenced by its process parameters and type of electrode. In this study, soft computing technique was utilized to optimize the performance of the EDM in roughing condition for eroding PCD with copper tungsten or copper nickel electrode. Central composite design with five levels of three machining parameters viz. peak current, pulse interval and pulse duration has been used to design the experimental matrix. The EDM experiment was conducted based on the design experimental matrix. Subsequently, the effectiveness of EDM on shaping PCD with copper tungsten and copper nickel was evaluated in terms of material removal rate (MRR) and electrode wear rate (EWR). It was found that copper tungsten electrode gave lower EWR, in comparison with the copper nickel electrode. The predictive model of radial basis function neural network (RBFNN) was developed to predict the MRR and EWR of the EDM process. The prominent predictive ability of RBFNN was confirmed as the prediction errors in terms of mean-squared error were found within the range of 6.47E−05 to 7.29E−06. Response surface plot was drawn to study the influences of machining parameters of EDM for shaping PCD with copper tungsten and copper nickel. Subsequently, moth search algorithm (MSA) was used to determine the optimal machining parameters, such that the MRR was maximized and EWR was minimized. Based on the obtained optimal parameters, confirmation test with the absolute error within the range of 1.41E−06 to 5.10E−05 validated the optimization capability of MSA. [ABSTRACT FROM AUTHOR]

Die-sinking electrical discharge machining is an unconventional technology that allows to machine all at least minimally electrically conductive materials regardless of their physical and mechanical properties. Despite the fact that it is not a conventional technology, the tool gets also worn out, which is a tool electrode. The wear of the electrode does not only mean its loss but also the degradation of the shapes that are transferred to the resulting workpiece. For this reason, a design of experiments was conducted with 6 input factors, 2 were categorical: the electrode material (copper, graphite) and workpiece material (steel 1.2363 and steel 1.2343ESR) and 4 were numerical: Open-voltage, Pulse current, Pulse on-time, and Pulse off-time. In the framework of this design of experiments, the wear of the used graphite and copper electrodes at their corners and edges was evaluated, which was made possible by the use of electron microscopy and the use of approximation circles. Furthermore, the eroding speed, the topography of the machined samples, and the morphology of the surfaces of the used electrodes were investigated. It has been recognized that the use of a graphite electrode will allow for more accurate workpiece shapes and less wear. [ABSTRACT FROM AUTHOR]