Near-dry electrical discharge machining (ND-EDM) is an eco-friendly process. In this study, an approach has been made to make the machining process more efficient than ND-EDM with the addition of metallic powder with the dielectric medium to machine EN-31 die steel. Powdermixed near-dry EDM (PMND-EDM) has several advantages over the ND-EDM or conventional electrical discharge machining (EDM) process, such as a higher material removal rate (MRR), fine surface finish (Ra), sharp cutting edge, lesser recast layer, and lower deposition of debris. The output response variables are MRR, Ra, residual stress (RS) and micro-hardness (MH) of the machined surfaces. Further study of the workpiece was performed, and a comparative study was conducted between ND-EDM and PMND-EDM. In this proposed method of machining, the MRR, Ra, and MH increased by 17.85 %, 16.36 %, and 62.69 % while RS was reduced by 56.09 %.
Highlights
• Experimental investigations have been conducted in the PMND-EDM process. The metallic powder (zinc) as an additive alongwith the mist of a dielectric medium was used for performance enhancements. • In PMND-EDM, the MRR was influenced by powder concentration. The MRR increases with the increase in metallic powder concentration, and the maximum increase in MRR was 17.85 %, as compared to ND-EDM. • The surface finish was improved by 16.36 % in PMND-EDM as the sparking is uniformly distributed among the powder particles, which gives even and uniform machined surfaces. • There was a decrease in residual stress by 56.09 % over the machined surfaces in PMND-EDM as compared to ND-EDM process. • The maximum increase in MH was 62.69 % over the machined surface in PMND-EDM as compared to ND-EDM.
The Powder-Mixed Near-Dry Electric Discharge Machining (PMND-EDM) methodology has proven to be efficient in terms of machining rate, surface morphology, and environmental friendliness, unlike traditional EDM. In this study, the presence of a conductive metallic powder (zinc) in the dielectric medium was responsible for changing the topography of the workpiece (EN-31) and resulted in a higher micro-hardness value of the machined component. In this research, an approach has been made to optimize the significant process parameters by using a Taguchi L9 orthogonal array (OA) to obtain machined components with higher values of micro-hardness, which was measured in terms of Vickers hardness HV. The selected process parameters were tool diameter, mist flow rate, metallic powder concentration, and dielectric mist pressure. By introducing foreign particles (metallic powder), the topography of the machined products has been improved, and the micro-hardness value was found to be enhanced. The confirmation experiment was performed for optimal process parameter settings, and the enhanced microhardness value was found to be 506.63 HV in the machined EN-31 die steel.
Gaseous assisted powder mixed near dry EDM (GAPMND-EDM) is one of the recent hybrid technologies, which not only enhance the machining performance, but at the same time, high quality products with better surface quality characteristics can also be achieved. In this study, the response parameters were material removal rate, surface finish, micro hardness and residual stress. It was found that the maximum material removal rate (MRR 3.379 mg/min) was achieved with combination of (dielectric) oxygen gas with graphite powder while lowest surface roughness (SR 1.11 μm) was found to be with dielectric argon gas with graphite additives. Highest micro hardness (MH) and lowest residual stress (RS) was 820.30 Vickers hardness number (VHN) and 229 MPa found with dielectric combination of zinc additives with argon gas.
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