Machining Characteristics and Parametric Optimisation of Inconel 825 during Electric Discharge Machining

This paper presents the machining characteristics and parametric optimisation of Inconel 825 during die-sinking electrical discharge machining (EDM) process. This work considers seven input parameters out of which six are of three levels and one is of one level. Metal removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) have been considered as performance measures. Before carrying out physical experimental runs, the experiments have been designed using Taguchi’s L36 (21 × 36) orthogonal array (OA). In order to identify the significant input parameters, Analysis of Variance has been employed on the experimental data. Discharge current, pulse-on-time, tool material and tool electrode lift time are found as significant input parameters. The effects of these significant parameters on the performance measures have been presented using Taguchi\u27s technique. After machining, study of surface characteristics of the electric discharged machined surface has been carried out using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDXS) and X-ray diffraction (XRD). These studies help in obtaining the information pertaining to topography of the machined surface, material transfer from tool and dielectric to the machined surface, and presence of extra element and their different phases at the machined surface. It has been found from the research that Carbon, Oxygen, Iron, Nickel, Chromium and little amount of Molybdenum are transferred to the surface of work piece. Further, for the best yield of the process, the optimal combination of input parameters has been obtained and reported using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) as a multi-objective optimisation technique. Consideration of two different dielectric fluids and three different electrode materials is the novelty of the work

Novel EDAS-Taguchi and EDAS-Taguchi-Pareto Methods for Wire EDM Process Parametric Selection of Ni55.8Ti (Nitinol) Shape Memory Alloy

The EDAS (evaluation based on distance from average solution) method is a broadly utilized tool for multi-criteria analysis with the ability to handle several conflicting criteria. The Taguchi method is an optimization tool with economic capability in experimentation. This article presents EDAS Taguchi (EDAS-T) method based on EDAS and the Taguchi method. It also presents EDAS Taguchi-Pareto (EDAS-TP) method framed from EDAS and Taguchi-Pareto methods. Furthermore, data from the literature to test the proposed methods are presented, which the results are compared. This research shows that the EDAS method produces the optimum combination of parameters at a run with a current of 4A, pulse on time of 50 µs, pulse off time of 14ms, and powder concentration of 1 g/L. Also, the EDAS-Taguchi method reveals a current of 4A, pulse on time of 60 µs, pulse off time of 14 µs, and powder concentration of 1 g/L. However, the principal result is that using the EDAS Taguchi-Pareto method, the optimal current is 3A, pulse on time is 60 µs, and powder concentration is 0.75g/L. The EDAS Taguchi-Pareto method eliminated the pulse off time and pulse on time, claiming that it is not significant to the system's optimum performance. The principal novelty of this article is that it introduces a mechanism of concurrently optimizing and selecting the wire EDM process parameters using the EDAS-Taguchi-Pareto method. The optimization is parallelly conducted as selection occurs, providing an initial notification to ascertain timely detection and control of local optimality of parameters to global optimization before final selection. This is unlike most evaluations, where optimization is done differently from the selection. This study is the first to develop and use EDAS methods for the WEDM process of Ni55.8Ti shape memory alloy

Modelling, Investigation of Process Responses, Surface Assessment and Parametric Optimization in Powder Mixed Electrical Discharge Diamond Grinding of TI6AL4V Utilizing Grey-Based Taguchi Approach

In this study, the powder mixed electrical discharge diamond grinding (PMEDDG) process was designed and a set-up for machining hard electrically conductive material surfaces built. The paper presents empirical models, investigation, an optimal setting of factors and the distinct surface production in the PMEDDG of Ti6Al4V with aluminium (Al) and silicon carbide (SiC) powder mixed dielectric fluid. The response surface methodology was applied to the modelling. One set of 32 experiments with Al powder and another set of 32 experiments with SiC powder mixed dielectric fluid were performed on a PMEDDG set-up. Current, pulse on time, wheel speed, duty cycle, and volumetric proportion of the powder were taken as input machining variables. Material removal rate and surface roughness were computed as outputs. The behaviour of the input factors against the responses was studied and compared with the SiC and Al powder mixed dielectric fluid used in the PMEDDG process. Further, scanning electron microscopy (SEM) investigations were carried out to determine the impact of different factors on the PMEDDG-produced surfaces as well as the effect of powder presence in the dielectric fluid on white recast layer thickness of the produced surfaces. The grey-based Taguchi approach was used to determine an optimal set of process variables when aluminium powder is used and a confirmation test was conducted on the optimal set to estimate the effectiveness of this approach

Principles and Characteristics of Different EDM Processes in Machining Tool and Die Steels

Electric discharge machining (EDM) is one of the most efficient manufacturing technologies used in highly accurate processing of all electrically conductive materials irrespective of their mechanical properties. It is a non-contact thermal energy process applied to a wide range of applications, such as in the aerospace, automotive, tools, molds and dies, and surgical implements, especially for the hard-to-cut materials with simple or complex shapes and geometries. Applications to molds, tools, and dies are among the large-scale initial applications of this process. Machining these items is especially difficult as they are made of hard-to-machine materials, they have very complex shapes of high accuracy, and their surface characteristics are sensitive to machining conditions. The review of this kind with an emphasis on tool and die materials is extremely useful to relevant professions, practitioners, and researchers. This review provides an overview of the studies related to EDM with regard to selection of the process, material, and operating parameters, the effect on responses, various process variants, and new techniques adopted to enhance process performance. This paper reviews research studies on the EDM of different grades of tool steel materials. This article (i) pans out the reported literature in a modular manner with a focus on experimental and theoretical studies aimed at improving process performance, including material removal rate, surface quality, and tool wear rate, among others, (ii) examines evaluation models and techniques used to determine process conditions, and (iii) discusses the developments in EDM and outlines the trends for future research. The conclusion section of the article carves out precise highlights and gaps from each section, thus making the article easy to navigate and extremely useful to the related research communit

A review on conventional and nonconventional machining of SiC particle-reinforced aluminium matrix composites

AbstractAmong the various types of metal matrix composites, SiC particle-reinforced aluminum matrix composites (SiCp/Al) are finding increasing applications in many industrial fields such as aerospace, automotive, and electronics. However, SiCp/Al composites are considered as difficult-to-cut materials due to the hard ceramic reinforcement, which causes severe machinability degradation by increasing cutting tool wear, cutting force, etc. To improve the machinability of SiCp/Al composites, many techniques including conventional and nonconventional machining processes have been employed. The purpose of this study is to evaluate the machining performance of SiCp/Al composites using conventional machining, i.e., turning, milling, drilling, and grinding, and using nonconventional machining, namely electrical discharge machining (EDM), powder mixed EDM, wire EDM, electrochemical machining, and newly developed high-efficiency machining technologies, e.g., blasting erosion arc machining. This research not only presents an overview of the machining aspects of SiCp/Al composites using various processing technologies but also establishes optimization parameters as reference of industry applications

Experimental investigation and optimisation in EDM process of AISI P20 tool steel

Electro Discharge Machining (EDM) is an extremely prominent machining process among newly developed non -traditional machining techniques for “difficult to machine” conducting materials such as heat treated tool steels, composites, super alloys, ceramics, hastelloys, nitralloy, nemonic alloys, carbides, heat resistant steels etc. In EDM, the material removal of the electrode is achieved through high frequency sparks between the tool and the work-piece immersed into the dielectric. The Material Removal Rate (MRR), Tool Wear Rate (TWR) and surface integrity are some of the important performance attributes of EDM process. The objective of EDM is to get high MRR along with achieving reasonably good surface quality of machined component.The machining parameters that achieve the highest MRR strongly depend on the size of the machining surface i.e. the engaged electrode and work-piece surface.With upcoming worldwide applications of AISI P20 machining has become an important issue which needs to be investigated in detail. The AISI P20 steel is applied by the tooling industry as material for injection molding tools. These steel are categorized as “difficult to machine” materials, since they posses greater strength and toughness. Therefore, AISI P20 steel is usually known to create major challenges during conventional and non- conventional machining.Keeping this in view, an experimental investigation to explore the productivity, quality, surface integrity, and accuracy on the EDM surface. The work has been carried out by conducting a set of experiments using AISI P20 tool steel work-piece with copper electrode. Important machining parameters like Discharge current (Ip), Pulse on Time(Ton), Pulse off Time (Toff ), Lift Time (Tup) and Work Time (Tw) are considered for investigation. The effect of the machining parameters on the responses such as MRR, TWR, Surface Roughness (SR), and Micro hardness were investigated. Now-a-days optimization and modeling of EDM process is a highly demanding r

Optimisation of electrical discharge machining for oxidation-free metallic nanoparticle synthesis of titanium alloy

Various materials and chemical synthesis techniques have been investigated to develop better-quality nanoparticles with uniform shapes, sizes, dimensions, and dynamic properties. The development of defined nanoparticles (NP) with specific properties is still in search; therefore, in the present work, an approach using electrical discharge machining (EDM) to generate nanoparticles is investigated. The established EDM process has been used to generate uniform nanoparticles with efficient surface-related properties. Electrical discharge machining is a widely used manufacturing process for producing precise and detailed parts, particularly dies, moulds, and other complex shapes. This process involves using an electrode to generate electrical discharges through a workpiece, melting and vaporising the material to achieve the desired shape. In recent years, this area has seen significant advances in improved surface finishing, greater flexibility and Increased accuracy and precision. These advancements have made EDM an even more valuable tool for a wide range of industries and enabled the production of high-quality parts with greater efficiency and precision. As a result of new advancements, this machine can synthesise nanoparticles in the form of waste derbies. In just the past few years, this has emerged as a phenomenon of exceptional interest for nanoparticle synthesis by EDM. It is generally agreed that EDM can synthesise nanoparticles. However, this is a matter of ongoing discussion and further optimisation and update. Some researchers have attempted to solve these problems, which are still under investigation. The present work proposes a simple way to address this issue using an optimisation process and to add oleic acid as a capping agent with dielectric and synthesis nanoparticles of titanium and copper. These results were measured using SEM, TEM, XRD, TGA/DTA and FT-IR approaches. These methods have demonstrated a marked improvement in the quality of material synthesis and produced oxidation-free nanoparticles. In synthesising Ti alloys and copper by electrical discharge machining, the main parameters affecting the synthesis were current, on-time, off-time, and tool gap. The present study was conducted using the RSM experimental design to develop NPs. The experimental findings and optimisation results, a current of 6A, a pulse-on time of 60 ns, a pulse-off time of 40 ns, and kerosene as the dielectric, enabled the fabrication of 10 mm to 20 μm spherical nanoparticles of titanium alloy and copper. High voltage was used to produce 100 to 200 μm sized particles. Oleic acid was used on the surface as a covering agent for the dielectric fluid to obtain oxidation-free particles. SEM Exhibit result of average 20 μm spherical size of particles and EDX revealed no other elements associated. FT-IR graph represents a functional group of oleic acid as a capping agent that prevents the particle from oxidation. XRD characterised the structural properties of synthesised particles to remain the same as before. No crystalline structure changes or phase changes are detected in the material property

A study on multi-criteria decision-making in powder mixed electric discharge machining cylindrical shaped parts

In life as well as in engineering, many times, it is necessary to choose the best option among many different options. That will be more difficult when the criteria given for the selection contradict each other. For example, when external cylindrical grinding, the minimum surface roughness requirement necessitates a small depth of cut and feed rate. The material removal rate will be reduced in this case, and this requirement will conflict with the maximum material removal rate requirement. To solve the above problem, a very useful tool is multi-criteria decision-making (MCDM). In this paper, for the first time, MCDM results for powder mixed discharge machining (PMEDM) cylindrical parts of SKD11 tool steel with copper electrodes have been presented. In this work, eighteen experiments with the L18 (16×53) design using the Taguchi method were conducted. Six main input process parameters include the powder concentration, the pulse current, the servo voltage, the pulse on time, and the pulse off time. To select an alternative that simultaneously ensures two criteria including minimum surface roughness (RS) and maximum material removal speed (MRS), four different MCDM methods including MAIRCA (Multi-Attributive Ideal-Real Comparative Analysis), MARCOS (Measurement of Alternatives and Ranking according to Compromise Solution), TOPSIS (Technique for order of preference by similarity to ideal solution), and EAMR (Area-based Method of Ranking) and two methods of criteria weight calculation including MEREC (Method based on the Removal Effects of Criteria) and Entropy methods were selected. The results of MCDM when PMEDM SKD11 tool steel cylindrical parts with two methods for weight determination and four methods for solving MCDM problem were evaluated. In addition, the best alternative to ensure simultaneous minimum RS and maximum MRS was proposed

Experimental analysis and optimization of EDM parameters on HcHcr steel in context with different electrodes and dielectric fluids using hybrid Taguchi-based PCA-Utility and CRITIC-Utility approaches

Industries demand stringent requirements towards economical machining without hindering the surface quality while cutting high carbon high chromium (HcHcr) steel. Electrical discharge machining (EDM) of HcHcr steel aims at reducing machining cost (i.e., maximize material removal rate (MRR) and minimize tool wear rate (TWR)) with good surface quality (i.e., minimize surface roughness (SR)). A comparative study was carried out on EDM of HcHcr D2 steel (DIN EN ISO 4957) by applying Taguchi L18 experimental design considering different electrode materials (copper, graphite, and brass), dielectric fluids (distilled water and kerosene), peak current, and pulse-on-time. The process performances were analyzed with respect to material removal rate, surface roughness, and tool wear rate. Pareto analysis of variance was employed to estimate the significance of the process variables and their optimal levels for achieving lower SR and TWR and higher MRR. Hybrid Taguchi-CRITIC-Utility and Taguchi-PCA-Utility methods were implemented to determine the optimal EDM parameters. Higher MRR of 0.0632 g/min and lower SR of 1.68 µm and TWR of 0.012 g/min was attained by graphite electrode in presence of distilled water as dielectric fluid compared to the brass and copper. Additionally, a metallographic analysis was carried out to study the surface integrity on the machined surfaces. Micrographic analysis of the optimal conditions showed lower surface roughness and fewer imperfections (lesser impression, waviness surface, and micro-cracks) compared to worst conditions

Experimental Studies on Machinability of Inconel Super Alloy during Electro-Discharge Machining: Emphasis on Surface Integrity and Metallurgical Characteristics of the EDMed Work Surface

Inconel alloys are Nickel-Chromium based high temperature super alloys widely applied in aerospace, marine, nuclear power generation; chemical, petrochemical and process industries. Execution of traditional machining operations on Inconel super alloy is quite difficult due to its very low thermal conductivity which increases thermal effects during machining operations. Inconel often exhibits strong work hardening behavior, high adhesion characteristics onto the tool face, and thereby alters cutting process parameters to a remarkable extent. Additionally, Inconel may contain hard abrasive particles and carbides that create excessive tool wear; and, hence, surface integrity of the end product appears disappointing. The extent of tool life is substantially reduced. Thus, Inconel super alloys are included in the category of ‘difficult-to-cut’ materials. In view of the difficulties faced during conventional machining, non-traditional machining routes like Electro-Discharge Machining (EDM), Wire Electro-Discharge Machining (WEDM), micro-machining (micro-electro-discharge drilling) etc. are being attempted for processing of Inconel in order to achieve desired contour and intricate geometry of the end product with reasonably good dimensional accuracy. However, low material removal rate and inferior surface integrity seem to be a challenge. In this context, the present dissertation has aimed at investigating machining and machinability aspects of Inconel super alloys (different grades) during electro-discharge machining. Effects of process control parameters (viz. peak discharge current, pulse-on time, gap voltage, duty factor, and flushing pressure) on influencing EDM performance in terms of Material Removal Rate (MRR), Electrode Wear Rate (EWR) and Surface Roughness (SR) of the EDMed Inconel specimens have been examined. Morphology along with topographical features of the EDMed Inconel work surface have been studied in view of severity of surface cracking and extent of white layer depth. Additionally, X-Ray Diffraction (XRD) analysis has been carried out to study metallurgical characteristics of the EDMed work surface of Inconel specimens (viz. phases present and precipitates, extent of grain refinement, crystallite size, and dislocation density etc.) in comparison with that of ‘as received’ parent material. Results, obtained thereof, have been interpreted with relevance to Energy Dispersive X-ray Spectroscopy (EDS) analysis, residual stress and micro-indentation hardness test data. Effort has been made to determine the most appropriate EDM parameters setting to optimize MRR, EWR, along with Ra (roughness average), relative Surface Crack Density (SCD), as well as relative White Layer Thickness (WLT) observed onto the EDMed work surface of Inconel specimens. Moreover, an attempt has been made to examine the ease of electro-discharge machining on Inconel work materials using Deep Cryogenically Treated (DCT) tool/workpiece. A unified attempt has also made to compare surface integrity and metallurgical characteristics of the EDMed Inconel work surface as compared to the EDMed A2 tool steel (SAE 304SS) as well as EDMed Titanium alloy (Ti-6Al-4V)