Showing papers on "Electrical discharge machining published in 2020"

Investigating the influence of WEDM process parameters in machining of hybrid aluminum composites

Abstract: This article presents an experimental investigation to assess the influence of input process parameters of machinability of wire electrical discharge machining (WEDM) process for machining of tripl...

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

Abstract: Among 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.

Surface Analysis of Wire-Electrical-Discharge-Machining-Processed Shape-Memory Alloys.

Abstract: Shape-memory alloys such as nitinol are gaining popularity as advanced materials in the aerospace, medical, and automobile sectors. However, nitinol is a difficult-to-cut material because of its versatile specific properties such as the shape-memory effect, superelasticity, high specific strength, high wear and corrosion resistance, and severe strain hardening. Anunconventional machining process like wire-electrical-discharge-machining (WEDM) can be effectively and efficiently used for the machining of such alloys, although the WEDM-induced surface integrity of nitinol hassignificant impact on material performance. Therefore, this work investigated the surface integrity of WEDM-processed nitinol samples using digital microscopy imaging, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. Three-dimensional analysis of the surfaces was carried out in two different patterns (along the periphery and the vertical plane of the machined surface) andrevealed that surface roughness was maximalat the point where the surface was largely exposed to the WEDM dielectric fluid. To attain the desired surface roughness, appropriate discharge energy is required that, in turn, requires the appropriate parameter settings of the WEDM process. Different SEM image analyses showed a reduction in microcracks and pores, and in globule-density size at optimized parameters. EDX analysis revealed the absence of wire material on the machined surface

Antibacterial coating of Ti-6Al-4V surfaces using silver nano-powder mixed electrical discharge machining

Abstract: Previous studies have revealed the potential of powder mixed electrical discharge machining (PMEDM) with regards to concurrently machining part geometry and coating an antibacterial layer on medical devices. This study is aimed at further demonstrating this potential. In order to do so, the PMEDM process was varied by adding different concentrations of silver nano-particles into the dielectric fluid and used to machine Ti-6Al-4V. Afterwards, the resulting machined and coated surfaces were characterized with regards to surface integrity, the coating layer's thickness, microhardness and chemical elements as well as antibacterial property. Material removal rate, tool wear and pulse signals were also analysed in order to give an insight on process feasibility. From both qualitative and quantitative results, it could be established that the surfaces machined and coated by PMEDM method have demonstrated a significant reduction of not only the amount of S. aureus bacteria, but also the number of bacterial clusters on the coating layer's surface. Moreover, the coating layer's silver content, which depends on the powder concentration suspended in the dielectric fluid, plays a vital role in the antibacterial property. As compared to surfaces without silver, surfaces containing approximately 3.78% silver content showed a significant decrease in both bacterial numbers and clusters, whereas a further increase in silver content did not result in a considerable bacterial number and cluster reduction. Regarding the machining performance, as compared to EDM without powder, machining time is remarkably decreased by using the PMEDM method.

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

Abstract: 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 community.

On the Investigation of Surface Integrity of Ti6Al4V ELI Using Si-Mixed Electric Discharge Machining.

Abstract: Surface modification is given vital importance in the biomedical industry to cope with surface tissue growth problems. Conventionally, basic surface treatment methods are used which include physical and chemical deposition. The major drawbacks associated with these methods are excessive cost and poor adhesion of coating with implant material. To generate a bioactive surface on an implant, electric discharge machining (EDM) is a promising and emerging technology which simultaneously serves as machining and surface modification technique. Besides the surface topology, implant material plays a very important role in surgical applications. From various implant materials, titanium (Ti6Al4V ELI) alloy is the best choice for long-term hard body tissue replacement due to its superior engineering, excellent biocompatibility and antibacterial properties. In this research, EDM's surface characteristics are explored using Si powder mixed in dielectric on Ti6Al4V ELI. The effect of powder concentration (5 g/L, 10 g/L and 20 g/L) along with pulse current and pulse on time is investigated on micro and nanoscale surface topography. Optimized process parameters having a 5 g/L powder concentration result in 2.76 μm surface roughness and 13.80 μm recast layer thickness. Furthermore, a nano-structured (50-200 nm) biocompatible surface is fabricated on the surface for better cell attachment and growth. A highly favourable carbon enriched surface is confirmed through EDS which increases adhesion and proliferation of human osteoblasts.

Surface roughness prediction of machined aluminum alloy with wire electrical discharge machining by different machine learning algorithms

Abstract: Aluminum alloys are preferred in aviation, aerospace and automotive industries because of their high strength and durability compared to their lightness. Precision production of parts is very important in such industries. Therefore, precision machining of aluminum, which is difficult to manufacture with traditional methods, with non-traditional methods such as wire electrical discharge machining (WEDM), is a very popular approach. Surface roughness has an impact on the important properties of materials such as strength, wear resistance and fatigue strength. Experimental determination of surface roughness of surfaces machined with WEDM is time consuming and costly. These cost and time losses can be eliminated by predicted surface roughness with machine learning algorithms. In this study, Al7075 aluminum alloy was machined with different parameters (voltage, pulse-on-time, dielectric pressure and wire feed) with WEDM. Each parameter is at 3 levels, so 81 experiments were carried out. The surface roughness of the machined surfaces was measured by surface profilometer. The lowest surface roughness was 2.490 μm machined at 8 V voltage, 8 μs pulse on-time, 25 bar dielectric pressure and 2 mm/min wire feed. The experiments for machining of Al7075 via WEDM were modeled by machine learning methods. Four different models of two different methods were used for the prediction of surface roughness values of machined samples with WEDM. These models were ELM, W-ELM, SVR and Q-SVR. All of the models were applied to the data set and the W-ELM model was the best performing model with the value of 0.9720 R2. Thus, the W-ELM model has excellent potential in manufacturing industry which produced parts with WEDM.

Enhancing the Surface Quality of Micro Titanium Alloy Specimen in WEDM Process by Adopting TGRA-Based Optimization.

Abstract: The surface measures of machined titanium alloys as dental materials can be enhanced by adopting a decision-making algorithm in the machining process. The surface quality is normally characterized by more than one quality parameter. Hence, it is very important to establish multi-criteria decision making to compute the optimal process factors. In the present study, Taguchi-Grey analysis-based criteria decision making has been applied to the input process factors in the wire EDM (electric discharge machining) process. The recast layer thickness, wire wear ratio and micro hardness have been chosen to evaluate the quality measures. It was found that the wire electrode selection was the most influential factor on the quality measures in the WEDM process, due to its significance in creating spark energy. The optimal arrangement of the input process parameters has been found using the proposed approach as gap voltage (70 V), discharge current (15 A) and duty factor (0.6). It was proved that the proposed method can enhance the efficacy of the process. Utilizing the computed combination of optimal process parameters in surface quality analysis has significantly contributed to improving the quality of machining surface.

Surface and subsurface damage of reaction-bonded silicon carbide induced by electrical discharge diamond grinding

Abstract: Reaction-bonded silicon carbide (RB-SiC) ceramic, one of the best candidates for large optical mirrors, is difficult to machine because of its high hardness and brittleness. A hybrid process called electrical discharge diamond grinding (EDDG) exhibits potential for improving the machinability of RB-SiC by combining electrical discharge machining (EDM) and diamond grinding. However, this hybrid process leads to damages that differ from those in conventional processes owing to the simultaneous actions of EDM and diamond grinding. In the present study, surface and subsurface damages induced by the interactions between EDM and diamond grinding during the EDDG of RB-SiC were examined. The effect of the discharge energy was considered. The surface and subsurface topographies and microstructures were characterized via scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. The EDM and grinding zones exhibited distinctive surface topographies and different dominant material removal mechanisms. An increase in the discharge energy facilitated ductile removal of the material and decomposition of SiC. Thus, a thinner subsurface damage layer was obtained compared with that in the less-thermally affected zone. The decomposed C and material migration tended to increase with the discharge energy. Owing to the interactions between EDM and diamond grinding, the subsurface was a mixture of amorphous/crystalline C, polycrystalline/nanocrystalline SiC, and a crystalline SiC matrix.

Critical analysis of surface integrity parameters and dimensional accuracy in powder-mixed EDM

Abstract: This study aims at evaluating the effectiveness of Powder-Mixed Electrical Discharge Machining (PMEDM) in improving the surface integrity. The surface quality has been analyzed in terms of ...

Application of TGRA-Based Optimisation for Machinability of High-Chromium Tool Steel in the EDM Process

Abstract: It is essential to establish multi-criteria decision-making for computing the optimal process factors required to enhance the performance of the electrical discharge machining (EDM) process. For this purpose, criteria decision-making based on the Taguchi–grey analysis was employed in this study. Several responses such as material removal rates, average surface roughness, microhardness, and average white layer thickness were chosen to evaluate machinability. From the existing factor combinations, the optimum electrical factors that resulted in improved surface performance measures were identified as a peak current of 5 A, gap voltage of 50 V, pulse on time of 18 µs, and pulse off time of 37 µs, with a standard deviation within 4.1%. The maximum high- and low-grade value shows that the peak current affects performance measures, as it is essential in determining the spark energy in the EDM process. Moreover, significantly improved surface performance measures were achieved using the optimal process parameter combinations for the EDM process.

Empirical Investigations during WEDM of Ni-27Cu-3.15Al-2Fe-1.5Mn Based Superalloy for High Temperature Corrosion Resistance Applications.

Abstract: Monel K-500, a nickel–copper based alloy, is a very hard and tough material. Machining of such hard and tough materials always becomes a challenge for industry and this has been resolved by wire electric discharge machining (WEDM), a popular non-conventional machining method used for machining tough and hard materials having complex shapes. For the first time reported in this present research work is an experimental investigation executed on Ni-27Cu-3.15Al-2Fe-1.5Mn based superalloy using WEDM to model cutting rate (CR) and surface roughness (SR) using response surface methodology (RSM). The process parameters have been selected as pulse-on time, pulse-off time, spark-gap voltage and wire-feed rate. Experiments have been planned according to the central composite design (CCD). The results show that pulse-on time has a direct effect on CR while the pulse-off time has a reverse effect. The CR increases as pulse-on time increases, and decreases as pulse-off time increases. SR increases as pulse-on time increases, and decreases as pulse-off time increases. Furthermore, increase in spark-gap voltage decreases CR and SR both. The wire feed-rate has a negligible effect for both the response parameters. The optimized values of CR and SR achieved through multi-response optimization are 2.48 mm/min and 2.12 µm, respectively.

Multi-response Optimization of WEDM Parameters Using an Integrated Approach of RSM–GRA Analysis for Pure Titanium

Abstract: Wire electrical discharge machining is widely used in the application where precision is of prime importance, especially for conductive materials. In this study, central composite design of response surface methodology is implemented to design the experiments for optimization of WEDM process parameter on pure titanium. The identified input process variables are pulse on time (Ton), discharge current and pulse off time (Toff), while surface roughness and material removal rate are the output variables. ANOVA was used to study significance and non-significance factors. Grey relational analysis has been used for obtaining an optimal parameter setting for WEDM process to maximize the cutting rate while reducing surface roughness for pure titanium, which is the most preferred material for aerospace and biomedical application. The optimized process parameters were found at Ton of 6 µs, Toff of 4 µs and discharge current of 6 A after implementing GRA technique. A very close relation has been obtained at an optimal condition using GRA after the validation trial.

Effect of WEDM Process Parameters on Surface Morphology of Nitinol Shape Memory Alloy

Abstract: Nickel–titanium shape memory alloys (SMAs) have started becoming popular owing to their unique ability to memorize or regain their original shape from the plastically deformed condition by means of heating or magnetic or mechanical loading. Nickel–titanium alloys, commonly known as nitinol, have been widely used in actuators, microelectromechanical system (MEMS) devices, and many other applications, including in the biomedical, aerospace, and automotive fields. However, nitinol is a difficult-to-cut material because of its versatile specific properties such as the shape memory effect, superelasticity, high specific strength, high wear and corrosion resistance, and severe strain hardening. There are several challenges faced when machining nitinol SMA with conventional machining techniques. Noncontact operation of the wire electrical discharge machining (WEDM) process between the tool (wire) and workpiece significantly eliminates the problems of conventional machining processes. The WEDM process consists of multiple input parameters that should be controlled to obtain great surface quality. In this study, the effect of WEDM process parameters on the surface morphology of nitinol SMA was studied using 3D surface analysis, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. 3D surface analysis results indicated a higher value of surface roughness (SR) on the top of the work surface and a lower SR on the bottom portion of the work surface. The surface morphology of the machined sample obtained at optimized parameters showed a reduction in microcracks, micropores, and globules in comparison with the machined surface obtained at a high discharge energy level. EDX analysis indicated a machined surface free of molybdenum (tool electrode).

Curved profiles machining of Ti6Al4V alloy through WEDM: investigations on geometrical errors

Abstract: Great biocompatibility and superior mechanical properties of titanium alloys (Ti6Al4V) stimulate the use of this material frequently in biomedical, defence, and aeronautical industries. In these applications, the end parts generally have complex curved profiles. Through conventional means of machining, complex profiles with high dimensional accuracy are not easily achievable due to difficult-to-cut nature of Ti6Al4V. Wire Electric Discharge Machining (WEDM) is a promising alternative to cut the complex features like angular and curved features. In this research, convex and concave profiles are machined in Ti6Al4V through WEDM. The influence of four machining parameters, namely servo voltage, wire feed, pulse On- and Off-time, over the geometrical accuracies of convex and concave profiles along with corner radii have been comprehensively investigated. The L27 orthogonal array was taken as the design of the experiment, and the results are evaluated in terms of statistical (ANOVA and signal-to-noise ratio) and microscopic morphology by Scanning Electron Microscopy (SEM). Optimized combination of machining parameters are sought capable of resulting in minimum geometric deviations (0.250% overcut in convex and 0.236% undercut in concave profiles) and corner radii of 0.106 mm. Moreover, the SEM analysis has confirmed that the discharge energy and erosion phenomenon significantly affect the profile accuracy as well as the surface integrity. In addition to optimized parameters the provision of wire offset, ranging within 0.169–0.173 mm, can further mitigate the geometric deviations of the actual machined profiles from the designed geometries.

Influence of micro size titanium powder-mixed dielectric medium on surface quality measures in EDM process

Abstract: The enhancement of the surface quality measures is still attracting great research attentions in electrical discharge machining. In the present investigation, an analysis was made to improve the surface performance measures in EDM process with different tool electrodes such as titanium, copper, and graphite electrodes under dielectric medium mixed with micro size titanium particles. The surface roughness, hardness, white layer thickness, crack formation, and surface topography were considered as surface quality measures. From the experimental investigation, it has been observed that surface hardness could be improved significantly with titanium powder-mixed dielectric medium due to its ability of changing conductivity of machining zone with copper tool electrode. The electrical and thermal conductivity of tool electrode and powder materials can strongly affect the quality of the machined surface in EDM process.

Recent Advances and Perceptive Insights into Powder-Mixed Dielectric Fluid of EDM.

Abstract: Electrical discharge machining (EDM) is an advanced machining method which removes metal by a series of recurring electrical discharges between an electrode and a conductive workpiece, submerged in a dielectric fluid. Even though EDM techniques are widely used to cut hard materials, low efficiency and high tool wear remain remarkable challenges in this process. Various studies, such as mixing different powders to dielectric fluids, are progressing to improve their efficiency. This paper reviews advances in the powder-mixed EDM process. Furthermore, studies about various powders used for the process and its comparison are carried out. This review looks at the objectives of achieving a more efficient metal removal rate, reduction in tool wear, and improved surface quality of the powder-mixed EDM process. Moreover, this paper helps researchers select suitable powders which are exhibiting better results and identifying different aspects of powder-mixed dielectric fluid of EDM.

Intelligent approach for process modelling and optimization on electrical discharge machining of polycrystalline diamond

Abstract: 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 647E−05 to 729E−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 141E−06 to 510E−05 validated the optimization capability of MSA

High Aspect Ratio Thin-Walled Structures in D2 Steel through Wire Electric Discharge Machining (EDM).

Abstract: Thin structures are often required for several engineering applications. Although thick sections are relatively easy to produce, the cutting of thin sections poses greater challenges, particularly in the case of thermal machining processes. The level of difficulty is increased if the thin sections are of larger lengths and heights. In this study, high-aspect-ratio thin structures of micrometer thickness (117-500 µm) were fabricated from D2 steel through wire electrical discharge machining. Machining conditions were kept constant, whereas the structure (fins) sizes were varied in terms of fin thickness (FT), fin height (FH), and fin length (FL). The effects of variation in FT, FH, and FL were assessed over the machining errors (FT and FL errors) and structure formation and its quality. Experiments were conducted in a phased manner (four phases) to determine the minimum possible FT and maximum possible FL that could be achieved without compromising the shape of the structure (straight and uniform cross-section). Thin structures of smaller lengths (1-2 mm long) can be fabricated easily, but, as the length exceeds 2 mm, the structure formation loses its shape integrity and the structure becomes broken, deflected, or deflected and merged at the apex point of the fins.

Application of Type-2 Fuzzy AHP-ARAS for Selecting Optimal WEDM Parameters

Abstract: Machining of the nickel-based alloy is very demanding due to its extreme mechanical properties, for example, higher fatigue strength, better corrosion and creep resistance feature, substantial work hardening capability, and appreciable tensile and shear strength. Owing to these properties, the selection of machining parameters is a major challenge for modern machining industries. Therefore, the present experimental work is carried out to select the best parametric combination of the wire electrical discharge machining (WEDM) machine for reducing machining cost and human effort. The Trapezoidal Interval Type-2 fuzzy number (T2FS) integrated Analytical Hierarchy Process (AHP)-based Additive Ratio Assessment (ARAS) method is used for selecting the best WEDM process parameters of Inconel-800 superalloy. Finally, the results were compared with some existing multi-criteria decision-making methods to confirm the validity of the adopted method. The comparison shows that Type-2 Fuzzy AHP-ARAS synergy can help to formulate the problem and facilitate the assessment and ranking of WEDM process parameters when multiple criteria are jointly considered.

Reduction of Energy Consumption and Thermal Deformation in WEDM by Magnetic Field Assisted Technology

Abstract: Energy consumption and machining accuracy are considered to be two important attributes of performance indicators for green operations of wire electric discharge machining (WEDM). However, there is a paucity of studies that focus on the energy consumption and geometric error caused by thermal deformation. In this paper, a hybrid technique of WEDM with assisted magnetic field (MF) is proposed for enhancing machining performance to reduce energy consumption and thermal deformation. Based on the principles of thermal deformation, energy consumption, and magnetic field-assisted WEDM, a set of experiments is conducted to investigate thermal deformation and energy consumption of MF-assisted WEDM and conventional WEDM machining of Inconel 718. The effects of magnetic field on thermal deformation, discharge waveforms, surface integrity, and energy consumption are analyzed, and it is concluded that the proposed hybrid technique of MF-assisted WEDM offers numerous advantages and potential for applications in the green precision manufacturing field.