Search Results (9)

Micro-electrical discharge machining is valuable in industry thanks to its ability to realise precise micro-holes with high aspect ratios. However, a limitation of the technology is represented by its low material removal rate compared to other material removal technologies. Therefore, different strategies are under investigation to make the process faster. One of these strategies consists of adding powders into the dielectric. This process is called powder-mixed electrical discharge machining (PMEDM). This paper focusses on the optimisation of different aspects of this process, particularly the effects of the powder concentration, the presence of the surfactant, the stirring of the dielectric during the machining and the stability in time of the dielectric in micro-drilling. Graphite was used as powder in pure water, and in some tests a dispersant was also added. The concentration of the powder was varied, maintaining the same ratio between the graphite and the surfactant. The optimal graphite concentration was also used without the dispersant but with a changed parameter for the stirring system. The powder-mixed dielectrics showed better removal performance than pure water, and the best graphite concentration was the highest. The material removal rate increased by 40–150% compared to pure water. The tests made without dispersant showed that its presence did not improve the machining rate, while the stirring system deeply affected the process. The electrode wear benefitted from the reduction in machining time, and when the dispersant was used, electrode wear was lowered up to 50% compared to pure water. The trend of the electrode law of motion was affected by the concentration of the contaminant (debris from the erosion and powder). The geometrical characteristics were also affected by the presence of the powder, which changed the spark length. With the highest graphite concentration, radial overcut increased up to 50% compared to pure water. The stability in time of the dielectric when the powder was added was also evaluated and it was found that an efficient stirring system without the use of dispersant is a good solution, able to limit the possible sedimentation and aggregation of the powder. Full article

Inconel 718’s exceptional strength and corrosion resistance make it a versatile superalloy widely adopted in diverse industries, attesting to its reliability. Electrochemical machining (ECM) further enhances its suitability for intricate part fabrication, ensuring complex shapes, dimensional accuracy, stress-free results, and minimal thermal damage. Thus, this research endeavors to conduct a novel investigation into the electrochemical machining (ECM) of the superalloy Inconel 718. The study focuses on unraveling the intricate influence of key input process parameters—namely, electrolytic concentration, tool feed rate, and voltage—on critical response variables such as surface roughness (SR), material removal rate (MRR), and radial overcut (RO) in the machining process. The powerful tool, response surface methodology (RSM), is used for understanding and optimizing complex systems by developing mathematical models that describe the relationships between input and response variables. Under a 95% confidence level, analysis of variance (ANOVA) suggests that electrolyte concentration, voltage, and tool feed rate are the most important factors influencing the response characteristics. Moreover, the incorporation of ANN modeling and the MOGA-ANN optimization algorithm introduces a novel and comprehensive approach to determining the optimal machining parameters. It considers multiple objectives simultaneously, considering the trade-offs between them, and provides a set of solutions that achieve the desired balance between MRR, SR, and RO. Confirmation experiments are carried out, and the absolute percentage errors between experimental and optimized values are assessed. The detailed surface topography and elemental mapping were performed using a scanning electron microscope (SEM). The nano/micro particles of Inconel 718 metal powder, obtained from ECM sludge/cakes, along with the released hydrogen byproducts, offer promising opportunities for recycling and various applications. These materials can be effectively utilized in powder metallurgy products, leading to enhanced cost efficiency. Full article

Electrical discharge machining (EDM) has emerged as a pivotal non-conventional production technique due to its unique capability to machine without the cutting tool’s physical contact with the workpiece, making it apt for brittle, delicate, and complex materials. This research delved into the influence of operational parameters—pulse duration (Ton), peak current (Ip), duty cycle (T), and gap voltage (Vg)—on machining attributes, namely material removal rate (MRR), electrode wear rate (EWR), and radial overcut (ROC) for AISI D2 steel. Utilizing the Taguchi L9 orthogonal array for experimental design, nine experiments were conducted, followed by signal-to-noise ratio (S/N ratio) computations. Key findings highlighted a 4.02 dB improvement in the S/N ratio for MRR, leading to a 29.13% improvement; a 10.35 dB enhancement in the S/N ratio for EWR, resulting in a 33.33% reduction; and a 2.20 dB increase in the S/N ratio for ROC, leading to a 28.57% increment. ANOVA analyses further underscored the predominant influence of all four parameters. The significance of these findings lies in optimizing the EDM process for increased efficiency, reduced tool wear, and enhanced precision, potentially leading to cost savings and improved production quality in industrial applications. Full article

Glass is a hard and brittle insulating material that is widely used in optics, biomedicine, and microelectromechanical systems. The electrochemical discharge process, which involves an effective microfabrication technology for insulating hard and brittle materials, can be used to perform effective microstructural processing on glass. The gas film is the most important medium in this process, and its quality is an important factor in the formation of good surface microstructures. This study focuses on the gas film properties and their influence on the discharge energy distribution. In this study, a complete factorial design of experiments (DOE) was used, with three factors and three levels of voltage, duty cycle, and frequency as the influencing factors and gas film thickness as the response for the experimental study, to obtain the best combination of process parameters that would result in the best gas film quality. In addition, experiments and simulations of microhole processing on two types of glass, quartz glass and K9 optical glass, were conducted for the first time to characterize the discharge energy distribution of the gas film based on the radial overcut, depth-to-diameter ratio, and roundness error, and to analyze the gas film characteristics and their effects on the discharge energy distribution. The experimental results demonstrated the optimal combination of process parameters, at a voltage of 50 V, a frequency of 20 kHz and a duty cycle of 80%, that achieved a better gas film quality and a more uniform discharge energy distribution. A thin and stable gas film with a thickness of 189 $\mathsf{\mu }$m was obtained with the optimal combination of parameters, which was 149 $\mathsf{\mu }$m less than the extreme combination of parameters (60 V, 25 kHz, 60%). These studies resulted in an 81 $\mathsf{\mu }$m reduction in radial overcut, a roundness error reduced by 14, and a 49% increase in the depth–shallow ratio for a microhole machined on quartz glass. Full article

The current experimental study concerns obtaining the optimal set of wire-EDM processing factors for a novel Al-Mg-0.6Si-0.35Fe/15%RHA/5%Cu hybrid aluminum matrix composite. The composite exhibits hardness of 64.2 HRB, tensile strength 104.6 MPa, impact energy 4.8 joules, when tested using standard testing techniques. For this, composite is formulated with the help of a stir casting route. The tests are conducted as per Taguchi’s L₂₇ OA, to explore the influence of processing factors on the surface roughness (Ra), radial overcut (ROC) and material removal rate (MRR). The optimization is executed using the Taguchi approach, followed by multiple objective optimizations with TOPSIS (one of the MADM techniques). For optimal values of Ra, MRR and ROC, the optimum set of input variables is suggested as 150 A of current, 125 μs of pulse duration, 50 μs of pulse interval and 8 mm/min of wire feed-rate. Predicted performance index value was calculated and was compared with the experiment value. It has been observed that both values are very close to each other with only 1.33% error, which means the results are validated. ANOVA confirms that current is a predominant factor influencing response characteristic parameters, which contributes 24.09%, followed by pulse duration (16.78%) and pulse interval (15.18%). The surface characterization using a scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectroscope (EDS) and optical microscope (OM) has also been carried out to affirm the existence of the reinforcing particles in the base matrix. Full article

Electro-discharge machining (EDM) is a useful non-conventional machining operation frequently applied to make different complex geometries in any conducting material. The objectives of the present paper are to study the effect of a variation of thermo-physical properties (TPP) of three different tool materials on EDM performances. The different performances compared in this paper are: material removal rate (MRR), tool-wear rate (TWR), surface roughness (SR), radial overcut (ROC), surface-crack density (SCD) and surface hardness. Two of the most widely used work piece materials, such as corrosion-resistant austenitic stainless steel (SS316) and high strength corrosion-resistance titanium alloy (Ti-6Al-4V), are machined with the help of three different tools by varying input current and maintaining constant pulse-on time, pulse-off time and flushing pressure. Microstructural studies of the tool tip surface after machining have also been carried out. It is found that among these three tool materials, the copper tool showed the best machining performance with respect to material removal rate, radial overcut, surface finish and surface-crack density. This work will help industry personnel to choose a suitable tool for a specific work piece material. Full article

Ti-6Al-4V is considered a challenging material in terms of accurate machining. Therefore, electric discharge machining (EDM) is commonly engaged, but its low cutting rate depreciates its use. This issue is resolved if graphene nanoparticles are mixed in the dielectric. However, the control over the sparking phenomenon reduces because of the dispersion of graphene particles. Subsequently, the machined profile’s geometric accuracy is compromised. Furthermore, the presence of nanographene induces different sparks along axial and radial cutting orientations. This aspect has not been comprehensively examined yet and dedicatedly targeted in this study to improve the quality of EDM process for Ti-6Al-4V. A total of 18 experiments were conducted under Taguchi’s L18 design considering six parameters namely, electrode type, polarity, flushing time, spark voltage, pulse time ratio, and discharge current. The aluminum electrode proved to be the best choice to reduce the errors in both the cutting orientations. Despite the other parametric settings, negative tool polarity yields lower values of axial (A_DE) and radial errors (R_DE). The developed optimal settings ensure 4.4- and 6.3-times reduction in R_DE and A_DE, respectively. In comparison to kerosene, graphene-based dielectric yields 10.2% and 19.4% reduction in R_DE and A_DE, respectively. Full article

Electric discharge machining (EDM) of tool steel (D2 grade) has been performed using different tool designs to produce through-holes. Machining performance has been gauged with reference to machining time, hole taper angle, overcut, and surface roughness. Inaccuracies and slow machining rate are considered as the most common limitations of the electric discharge machining (die-sinking). Traditionally, a cylindrical tool is used to form circular holes through EDM. In this study, the hole formation is carried out by changing the tool design which is the novelty of the research. Two-stage experimentation was performed. The newly designed tools substantially outperformed a traditional cylindrical tool, especially in terms of machining time. The main reason for the better machining results of modified tools is the sparking area that differs from the traditional sparking. Comparing against the performance of a traditional cylindrical tool, the newly designed tools offer a considerable reduction in the machining time, radial overcut, and roughness of the inside surfaces of machined holes, amounting to be approximately 50%, 30.6%, and 38.7%, respectively. The drop in the machining time along with a condensed level of radial overcut and surface roughness can shrink the EDM limitations and make the process relatively faster with low machining inaccuracies. Full article

Among the family of carbides, tungsten carbide (WC) and its variants have extensive use in numerous applications including cutting tools, dies, and many wear resistant parts. Such applications need machining of WC, which is famously considered as challenging due to high tool wear mainly in traditional machining. Sinking electric discharge machining (EDM) can be considered as a suitable alternate but the low machining rate of EDM, with conventional tool design, poses limitations. In this research, the conventional tool design is modified by providing relief angles to the tool electrodes. The relief-angled tool electrodes are first time introduced in this research to machine through holes. The role of the relief angle during EDM has been investigated in terms of six response characteristics, i.e., machining time, hole taper angle, radial overcut at the hole entrance, radial undercut at the hole exit, longitudinal tool wear, and roughness of inside hole surfaces. The performance of the relief-angled electrodes is found to be significantly better than the performance of conventional cylindrical tool. In addition to improvements in other responses, a 49% reduction in the machining time has been realized by the use of relief-angled electrode indicating a worthwhile contribution in the field of electric discharge machining. Full article