30 research outputs found

    Powder Mixed Electrical Discharge Machining and Biocompatibility: A State of the Art Review

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    Electrical Discharge Machining (EDM) is a well-known process for machining of difficult to cut materials. Along with adding the powder in dielectric liquid, change in properties of machining gap results in a variety of sparks forms and lead different mechanisms under specific operational conditions during machining. The discharge models significantly differ from conventional EDM and leave its characteristics surface features. Primary studies of Powder Mixed Electrical Discharge Machining (PMEDM) focused on the understanding of material removal rate, surface quality, and tool wear rate concerning the widespread of the operational conditions evolved in the process. Then, the interactions with the powder material during discharging and the resultant surface properties impel the researcher's interest to achieve functional surfaces. In this respect, PMEDM is a significant concern in recent years as an alternative and simple production technique to obtain functional surfaces for specific needs. Nowadays, among the specific needs, production of biocompatible surfaces with the use of the technique provides a challenging opportunity to the researchers to address osseointegration issues. The study presents an introduction and review of the research work in PMEDM. The studies concerning machining efficiency, surface integrity, and generation of functional surfaces are presented and discussed in the light of current research trends. Attempts made to improve biocompatible surfaces with the use of the process also included to clarify the future trends in PMEDM

    Powder-mixed Electric Discharge Machining (PMEDM) of Inconel 625

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    In recent times, nickel-based super alloys are widely used in aerospace, chemical and marine industries owing to their supreme ability to retain the mechanical properties at elevated temperature in combination with remarkable resistance to corrosion. Some of the properties of these alloys such as low thermal conductivity, strain hardening tendency, chemical affinity and presence of hard and abrasives phases in the microstructure render these materials very difficult-to-cut using conventional machining processes. Therefore, the aim of the current research is set to improve the productivity and surface integrity of machined surface of Inconel 625 (a nickel-based super alloy) by impregnating powder particles such as graphite, aluminum and silicon to kerosene dielectric during electric discharge machining (EDM). Initially, temperature distribution, material removal rate (MRR) and residual stress were predicted through numerical modelling of powder-mixed EDM (PMEDM) process. In the experimental investigation, particle size analysis of the as-received powder particles was carried out to identify the distribution of particles. X-ray diffraction (XRD) analysis of particles indicated the presence of various phases including small amount of impurities. An experimental setup was developed and integrated with the existing EDM system for carrying out PMEDM process. The experiments were planned and conducted by varying five different parameters such as powder concentration, peak current, pulse-on time, duty cycle and gap voltage according to the central composite deign (CCD) of response surface methodology (RSM). Effects of these parameters along with powder concentration were investigated on various EDM characteristics such as material removal rate (MRR), radial overcut (ROC) and surface integrity aspects including surface crack density (SCD), surface roughness (SR), altered layer thickness (ALT), microhardness of surface and sub-surface regions, chemical and metallurgical alterations of the machined surface and residual stress. Results clearly indicated that addition of powder to dielectric has significantly improved MRR and surface integrity compared to pure dielectric. Among the powders used, graphite has resulted in highest MRR, lowest SCD, least ALT, least microhardness of surface and sub-surface regions. Least ROC, lowest surface roughness and least residual stress were obtained using silicon powder. Aluminum performed well in terms of MRR at low concentration range (upto 6 g/l).Therefore, optimal process performance under a given operating condition depends on judicious selection of powder materials, their size, concentration and process parameters

    Micro-Electro Discharge Machining: Principles, Recent Advancements and Applications

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    Micro electrical discharge machining (micro-EDM) is a thermo-electric and contactless process most suited for micro-manufacturing and high-precision machining, especially when difficult-to-cut materials, such as super alloys, composites, and electro conductive ceramics, are processed. Many industrial domains exploit this technology to fabricate highly demanding components, such as high-aspect-ratio micro holes for fuel injectors, high-precision molds, and biomedical parts.Moreover, the continuous trend towards miniaturization and high precision functional components boosted the development of control strategies and optimization methodologies specifically suited to address the challenges in micro- and nano-scale fabrication.This Special Issue showcases 12 research papers and a review article focusing on novel methodological developments on several aspects of micro electrical discharge machining: machinability studies of hard materials (TiNi shape memory alloys, Si3N4–TiN ceramic composite, ZrB2-based ceramics reinforced with SiC fibers and whiskers, tungsten-cemented carbide, Ti-6Al-4V alloy, duplex stainless steel, and cubic boron nitride), process optimization adopting different dielectrics or electrodes, characterization of mechanical performance of processed surface, process analysis, and optimization via discharge pulse-type discrimination, hybrid processes, fabrication of molds for inflatable soft microactuators, and implementation of low-cost desktop micro-EDM system

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

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    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

    Effect of chromium (cr) particle size and span-20 surfactant on Aisi d2 hardened steel using electrical discharge machining

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    Existing manufacturing industries are facing challenges from modern advanced materials such as composite, super alloys, and hardened steels, which are hard and difficult to machine and process. Since it is not suitable to use conventional machining of the hard material, non-conventional machining such as electrical discharge machining (EDM) is one of the ideal techniques in dealing with these materials. However, the limitations of EDM will cause lower productivity and poor surface quality. Therefore, Powder Mixed Electrical Discharge Machining (PMEDM) has emerged as one of the advanced and innovative technique to eliminate the some of the disadvantages of EDM method. The fine powder particles are added into the tank then the spark gap is filled up with these additives particles. These electrically conductive powder particles reduce the insulating strength of dielectric fluid and increase the spark gap distance between tool electrode and workpiece, which due to this EDM process becomes more stable, thereby improving the EDM efficiency and quality of the machined surface. This research emphasizes the machining of AISI D2 hardened steel with EDM through adding both of micro and nano chromium powder mixed and span-20 surfactant using copper tool electrode. Then, machining productivity (i.e material removal rate (MRR), electrode wear rate (EWR) and surface roughness (Ra) and surface characteristics were investigated in terms of surface morphology, surface topography, recast layer thickness (RL) and microhardness. It was indicated that the addition of micro-nano chromium powder and span-20 surfactant to the dielectric notably enhanced the machining efficiency and better surface quality. The highest improvement 35~46 % of MRR, 29~69 % of Ra and 42~54 % of RL were attained at combination of micro-nano chromium powder and span-20 surfactant, respectively. There is no significant effect on EWR. For this purpose, full factorial 32 design of experiments (DOE) was chosen which consists of three levels of PMEDM parameters of chromium powder concentrations (Cp) and Span- 20 surfactant concentrations (Cs) for both micro and nano chromium powder. Response Surface Methodology (RSM) was utilized for responses optimization and Central Composite Design (CCD) was applied in designing the experiments to evaluate the effects of PMEDM parameters to three responses, MRR, EWR and Ra. Thus, this is clarify that the potential of addition of Cr powder and span-20 surfactant into dielectric fluid ability to gives a notable potential to be utilized as one of innovative technique, improving efficiency and better surface quality

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

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    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 optimization of machining performances and recent developments in electro discharge machining

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    Electro discharge machining (EDM) is a popular unconventional machining process widely employed in die-making industries. Careful selection of process parameters such as pulse current, voltage, on and off time, etc. is essential for machining of hard and conductive materials using EDM. Previous researchers working in the area of EDM have extensively analyzed the machining performance through experimental study, modeling, and simulation and also by theoretical analysis. This article discusses the significant summary of the work performed by earlier researchers through a detailed literature survey. Relevant literature on EDM and impact of process parameters on performance measures such as surface quality, tool wear rate and material removal rate are reviewed. The challenge and limitation of EDM process are also highlighted in this article. It is observed that optimization of process parameters is essentially required for effective and economical machining. So, this article addresses the various issues related to EDM and also provides brief insight into some of the current generation applications of EDM process explored in various industries

    Studies on Some Aspects of Multi-objective Optimization: A Case Study of Electrical Discharge Machining Process

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    Electrical Discharge Machining (EDM) finds extensive application in manufacturing of dies, molds and critical parts used in the automobile and other industries. The present study investigates the effects of different electrodes, deep cryogenic treatment of tools subjected to different soaking duration and a hybrid approach of powder mixed EDM of cryogenically treated electrodes on machinability of Inconel 718 super alloy. Inconel 718 has been used as the work material owing to its extensive application in aerospace industries. A Box– Behnken design of response surface methodology (RSM) has been adopted to estimate the effect of machining parameters on the performance measures. The machining efficiency of the process is evaluated in terms of material removal rate (MRR), electrode wear ratio (EWR), surface roughness, radial overcut and white layer thickness which are function of process variables viz. open circuit voltage, discharge current, pulse-on-time, duty factor and flushing pressure. In this work, a novel multi-objective particle swarm optimization algorithm (MOPSO) has been proposed to get the Pareto-optimal solution. Mutation operator, predominantly used in genetic algorithm, has been introduced in the MOPSO algorithm to avoid premature convergence and to improve the solution quality. To avoid subjectiveness and impreciseness in the decision making, the Pareto-optimal solutions obtained through MOPSO have been ranked by the composite scores obtained through maximum deviation theory (MDT). Finally, a thermal model based on finite element method has been proposed to predict the MRR and tool wear rate (TWR) when work piece is machined with variety of electrode materials. A coupled thermo-structural model has been also proposed to estimate the residual stresses. The numerical models were validated through experimentations. Parametric study is carried out on the proposed model to understand the influence of important process parameters on the performance measures. The study offers useful insight into controlling the machining parameters to improve the machining efficiency of the EDMed components

    Recent Developments in Wire EDM: A Review 1

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    Abstract Wire Electrical Discharge Machining is a controlled machining process which is used to manufacture geometrically intricate shapes with great accuracy and good surface finish that are difficult to machine with the help of conventional machining processes. WEDM is now growing as an important process in various fields; work has been done to use the technology for fabricating micro components. In this paper a review of the recent work has been done. Some properties and parameters that effects the machining performance of WEDM are also discussed
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