Electro Discharge Research Articles

Hydroxyapatite Electro Discharge Coating of Zr-Based Bulk Metallic Glass for Potential Orthopedic Application

In the past, Electro Discharge Machining (EDM) process was well known in cutting extremely hard materials and fabricating complex shapes. Recently, EDM process has been hybridized to not only shape, but also coats the surface of workpiece material. In this study, the deposition of hard carbide and calcium-based oxides on the Zr-based bulk metallic glass (BMG) using hydroxyapatite mixed electro discharge coating (HAm-EDC) have been investigated. The aim is to enhance the biocompatibility and cell adhesion of the BMG as a potential implant. The chemical composition, morphology and thickness of the coated surface were characterized through Optical Microscope, Scanning Electron Microscopy (SEM), X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). Major hydroxyapatite elemental composition (Ca, P, O), carbides (ZrC, TiC) and oxides (ZrO, CaZrO3) were formed on the treated BMG surface. A coating of about 23 µm thick was achieved. The addition of hydroxyapatite powder in the dielectric fluid enhances the Zr-based BMG surface quality by reducing the surface cracks and the crater size.

WEAR MECHANISM MAP OF MAGNESIUM ALLOY COATED WITH WC/CU ELECTRODE USING ELECTRO DISCHARGE ALLOYING

The objective of this research is to study the wear mechanism of ZE41A magnesium alloy coated with WC/Cu material using EDC (Electro discharge coating). Dry sliding experiments were conducted with pin on disc method with different sliding condition such as normal load (1.5 kg - 3.5 kg), sliding speed (100rpm - 300 rpm) and sliding time (3min - 7min). Wear mechanism map was drawn against sliding condition of normal load and sliding speed which has been utilized to study the dominance of particular wear mechanism that dominates a particular wear regime. Different wear regime such as mild wear, severe wear ultra severe wear was developed by adjustment of contour line of the wear rate map. Various mechanisms such as abrasion, oxidation, delamination, plastic deformation and melting were observed in the worn surface

Advanced machining of TiNiCo shape memory alloys for biomedical applications

Wire electro discharge machining (WEDM) is one of the most productive non-traditional machining processes. Complex shapes can be cut through the WEDM process. In the present study, attempts have been made to study the effects of various process parameters of WEDM such as pulse on time (T on), pulse off time (T off), servo voltage (SV), wire speed (WS) and servo feed (SF) on the material removal rate (MRR) and surface roughness (SR) for machining of TiNiCo shape memory alloys, traditionally used as bone staple material. Grey-relational-analysis-based entropy measurement methods were used for formulating a hybrid combination of optimisation methods, in order to investigate the input parameters of WEDM on the comprehensive performance of a bone staple material’s SR and MRR. Experiments were carried out by using response surface design (L-33), and the input parameters were ranked based on the grey relational grade. An experimental run was conducted using the optimal combination of input parameters of WEDM, which was obtained from the analysis. T on of 125 μs, T off of 42 μs, SV of 40 V, SF of 2180 machine units and WS of 4 m/min were obtained as the best combination of input process parameters for TiNiCo alloy.

Assistive Electro Discharge Machining of AIN Ceramics

Electro discharge machining process experiences limitation due to the non-conductive nature of the workpiece material. However, researchers proposed assistive EDM technique to machine nonconductive materials in the past. These assistive techniques require a minimal thickness of 100 µm conductive coating on the workpiece surface which usually takes longer time to coat the surface using PVD (physical vapor deposition) method. In this paper, a new modified assistive EDM method has been proposed to machine nonconductive Aluminum Nitride ceramics successfully. A three layers coating was used that included silver coating, carbon tape and silver nano-powder on a non-conductive aluminium nitride. This coating aids in conducting EDM operation due to the availability of conductive particles. Apart from the decomposition of dielectric that facilitates carbon particles on top of conductive carbon layer, coating itself also contributes in conductive silver particles. Therefore, carbon as well as silver debris that remains on the ceramics surface aids in continuous spark generation which in turn creates alternative thermal load and thus removes materials.

Obróbka elektroerozyjna kompozytów na osnowie z azotku krzemu i węglika krzemu

The paper presents the results of physical and mechanical properties of the and Si3N4 and SiC matrix ceramics with additives of good electrical conductivity carbides, nitrides and borides phases. The density, Young’s modulus, hardness HV1 and electrical conductivity of each material were investigated. Ceramic composite materials with the participation of the conductive phases have been produced using SPS (spark plasma sintering) method. Materials characterized by good electrical conductivity were shaped using EDM (electro discharge machining) method.

Machining and Characterization of Channels and Textures on Quartz Glass Using μ-ECDM Process

Applications of various glass materials like sodalime, borosilicate and pyrex are growing in the field of micro-electro mechanical systems. Quartz glass composes of pure silicon dioxide which is well- known for its hardness and processing of it would widen the scope of its application in product miniaturization. Micro-Electro Chemical Discharge Machining (μ-ECDM) is a non-conventional hybrid technique which combines the features of Electro Chemical Machining (ECM) and Electro Discharge Machining (EDM). In the present paper, channels are machined using μ-ECDM on 4 mm thick quartz glass with 370 μm diameter stainless steel (SS) tool. Experiments are designed at various levels of voltage (V), electrolyte concentration (wt%C) and duty factor (%DF) for parametric study. Signal to Noise (S/N) ratio and Grey Relational Analysis (GRA) are used to optimize the process parameters to enhance responses individually and simultaneously. The obtained S/N ratio optimized parameters to maximize Material Removal Rate (MRR) are - 60 V, 30 wt%C, 60 %DF resulted in 753 μg/min, to minimize Tool Wear Rate (TWR) are – 40 V, 20 wt%C, 50 %DF resulted in 2.99 μg/min and to minimize width of the channel are- 40 V, 20 wt%C, 60 %DF resulted in 500 μm. The GRA optimized parameters are- 40 V, 20 wt%C and 50 %DF resulting in 81 μg/m of MRR, 2.99 μg/m of TWR and 557.6 μm of width with entropy technique- equal weightage. Further an attempt has been made to machine texture on the quartz surface which is still in its early stages of research. GRA optimized parameters as detailed above are used to machine channels and generate textures of 45° hatch, square hatch and 45° criss-cross hatch on quartz glass.

Artificial neural network modelling and analysis of carbon nanopowder mixed micro wire electro discharge machining of gold coated doped silicon

Artificial neural network modelling and analysis of carbon nanopowder mixed micro wire electro discharge machining of gold coated doped silicon

Optimisation of EDM process parameters for AA7050-10 (WT) % B<SUB align="right">4C composite through ARAS, grey and Taguchi technique

The present paper discusses the development of AA7050-10(wt.) % B4C composite through flux assisted stir casting method and its machinability using die sinking EDM. Taguchi L16 orthogonal array were used to perform experiments. Material removal rate, surface roughness and tool wear rate were evaluated as machinability measure by considering the concurrent effect of various process parameters. The collected responses were optimised using additive ratio assessment (ARAS) and grey relation analysis and Taguchi technique. Pulse current of 16 A, pulse on time of 200 μs, and pulse off time of 30 μs were obtained as the optimum machining parameters. The validity of the Taguchi analysis was further verified by conducting a confirmation experiment. The error estimation for both methods is less than 5%. However, ARAS method gives the least percentage error than grey relation analysis. Hence, ARAS model is suitable to optimise the process parameters of electro discharge machining.

Wire Spark Erosion Machining of Ni rich NiTi Shape Memory Alloy for Bio-Medical Applications

The application of NiTi shape memory alloys are growing day by day in biomedical industry. These materials present inherent problems when undergoing conventional machining processes during manufacture of bioimplants. Conventional machining processes require high consumption of energy and resources, and assistance of post processing operations to make high quality implants of shape memory alloys. Unlike conventional methods, nonconventional methods are capable to eliminate the need for post processing amongst other advantages and thus prove to be the most economic means of producing biomedical implants. Wire spark erosion machining (also known as Wire Electro Discharge machining i.e. Wire-EDM) is one such nonconventional machining process that has been explored for the machining of biomedical implants by Ni rich NiTi. The present study aims to analyze and optimize the machinability of Ni55.8Ti shape memory alloy during wire electric discharge machining for biomedical applications. The L16 Orthogonal array using Taguchi design of experiments has been employed for this experimental study. The variable input parameters are namely pulse on time, pulse off time, servo voltage and wire feed rate. Machining at optimum parameters produced good surface finish, high material removal rate and excellent surface integrity. In this paper, specifically, the effect of the aforementioned Wire-EDM parameters on cutting rate, process optimization for the highest cutting rate, and surface roughness obtained at optimum parameters are reported. The outcomes encourage exploring wire spark erosion machining of other shape memory alloys for different scientific and industrial applications.

Development of a model to compensate overcut during electro discharge boring process

Development of a model to compensate overcut during electro discharge boring process

A review on optimization of machining performances and recent developments in electro discharge machining

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.

Modelling and Simulation Based Surface Characterization of Reverse- µEDM Fabricated Micro Pin-fins

Cross-sectional profile and surface quality of micro-fins of a heat sink play a significant role in the transmission of heat from microelectronic and MEMS devices subjected to intense heating. Several processes are available for the fabrication of such pin-fins, Reverse micro electro discharge machining (RµEDM) among them is one of the most promising. A wide range of parameters associated with this process provides varying competence for surface roughness. An effectively modeled and simulated surface, thus, may serve as a database for an operator to study the effect of parameters for the desired surface. A single discharge model is developed to study the volume removal by each discharge pulse to achieve the goal. ANSYS finite element code is used to simulate the process to find the volume of the crater for further prediction of average surface roughness values. The model’s predictions are compared with experimental results for verifying the approach and presented a good agreement with them.

Modern Optimization Techniques for Advanced Machining Processes – A Review

Abstract A review about the optimization techniques used for modern machining techniques are analyzed in this paper. The chief focus is kept on the modern optimization techniques employed to obtain the optimal machining parameters and during both non-conventional machining processes. The various Non-traditional machining techniques analyzed for this study are the Wire Electro Discharge Machining (WEDM), Laser Beam Machining (LBM), Abrasive Water Jet Machining (AWJM) and Electro Discharge Machining (EDM). These machining processes were analyzed with respect to different modern optimization techniques. The most widely used, frequently used and rarely used optimization techniques for the mentioned non-conventional machining processes are identified. The paper provides an overall idea about the optimization techniques and helps to choose the suitable technique for the researchers.

Artificial neural network modelling and analysis of carbon nanopowder mixed micro wire electro discharge machining of gold coated doped silicon

This research aims to machine gold coated doped Silicon (Si) wafer using micro wire electro discharge machining or uWEDM process in the presence of carbon nanopowder mixed dielectric oil. Effects of uWEDM parameters namely voltage, capacitance, powder concentration and coating thickness on average surface roughness (ASR), material removal rate (MRR) and spark gap (SG) have been analysed. All the three output parameters, i.e. material removal rate (MRR), spark gap (SG) and average surface roughness (ASR) were found to follow the parabolic trend with the variation of the nanopowder concentration. SG and ASR both were observed to be increased with the coating thickness. However, MRR was decreased with the same. An Artificial neural network based technique was used to model various responses. The overall model prediction was found to be in good agreement (average error less than 10%) with the experimental results for the corresponding input process parameters.

Development of a model to compensate overcut during Electro Discharge Boring process

Electro discharge boring (EDB) process is novel concept of machining through X-Y tool actuation applied for boring of hard and difficult to machine materials. Unlike conventional boring machining, EDB process is free from vibration, cutting forces or tool deflection. Since, the removal of material takes place due to the action of repetitive sparks therefore overcut is observed in the bored cavity produced during EDB process. In the present study, an effort has been made to predict and reduce the overcut generated during EDB process. Effect of process parameters on overcut have been studied using Taguchi's experimental method and then significant process parameters have been identified using analysis of variance method. Further, a prediction model has been developed using multiple regression analysis for prediction of overcut produced during boring process on Inconel 718 material. Finally, an algorithm has been developed in MATLAB software for compensation of overcut by suggesting compensating orbital radius for specified target diameter of cavity. The test results obtained using proposed algorithm show that the cavities generated are very close to the specified target cavities. [Submitted 3 September 2016; Accepted 24 July 2018]

External force assisted electro discharge machining of SS 316

Abstract Hybrid electro discharge machining came into the scenario of macro machining due to the need of more rapid machining process with improved efficiency of non conventional machining process. Electro-Discharge Machining (EDM) is a kind of non conventional machining specially used for drilling the holes of required dimensions aspect ratio. Earlier, vibration assisted EDM had came into existence to improve the efficiency such as increase in the metal removal rate, reduction in the electrode wear rate, and decrease in radial overcut of the surface of machined workpiece. But this technique of vibration assisted EDM process did not proved to be successful due to some disadvantages like increase in tool wear for low melting and comparatively softer tool material. Also vibration of workpiece material affects the circularity of holes produced by EDM process. There always exist a need for more advanced hybridised process to improve the overall machining efficiency specially circular shape and radial overcut. In this paper, an external force assisted called permanent magnetic field force assisted EDM process has been carried out with tungsten carbide tool of 5 mm diameter and SS 316 plate of 1.6 mm thickness. Measured performance characteristics like electrode or tool wear rate and diametral overcut represented satisfactory results with permanent magnetic field induced EDM process. The effects on MRR, TWR and diamteral overcut of SS 316 have been analyzed by the related software. It has been found that tool wear and diametral overcut has been found to be reduced with magnetic field assisted EDM than conventional EDM process. Also, machining time is reduced to a certain extent with this new technique of hybridisation.

Framework of models for selecting manufacturing processes and associated parameters for surface topographies

Choosing appropriate manufacturing processes to create functional surfaces is a challenging issue for some industrials. A specific surface finish can be obtained by different manufacturing processes, each of them having a different economic impact. Currently, no tool could guarantee the surface function through the choice of a manufacturing process and its associated operating parameters. This paper aims at discussing about a framework of models for selecting conventional or innovative manufacturing processes and their associated parameters with regards to surface topographies and textures. To achieve this, a concept of decomposition of database is introduced. Manufacturing processes such as, electro discharge machining, water jet machining (used for texturing surfaces), sandblasting and laser cladding are modelled. Finally, a concept that links such a database with computer aided design (CAD) software in order to integrate surfaces functionalities and manufacturing processes directly into the design step is discussed.

Parametric study of electrochemical discharge drilling on ceramic material using Taguchi method

The Electrochemical Discharge Machining (ECDM) is a hybrid machining technology which combined with electro discharge machining and electro chemical machining process. In this research, electrochemical discharge drilling operation is carried out on conventional ceramic tile by using a designed and manufactured ECDM setup. The experiments were performed as per design of experimental technique of Taguchi L27 orthogonal array using MINITAB 17 software. The important process parameters that have been selected are voltage, rotation and electrolyte concentration with output response as machining depth and diametric cut. From the observations, it is found that the voltage is the most significant parameter for machining depth and diametric cut followed by electrolyte concentration and rotation.

Performance analysis of a thick copper-electroplated FDM ABS plastic rapid tool EDM electrode

The importance of rapid tooling (RT) and additive manufacturing (AM) appears to be indispensable for boosting the process of manufacturing and expanding the horizon of production technology worldwide. This concept draws the attention of numerous scholars to arrive at a conclusive theory for the widespread utilization of RT. This study attempts to determine the viability and performance of an RT electrode in the field of electro discharge machining (EDM). The electrode prototype is made using an acrylonitrile butadiene styrene (ABS) plastic by fused deposition modeling (FDM), an AM technique, electroplated with copper of desired thickness, and used in die sinking EDM of D2 steel. The scanning electron microscope analysis of the electroplated samples confirms that it is possible to obtain the desired thickness of the metal by electroplating on any electrically conductive surface. In the present work, an experimental study is performed for examining the electroplated copper thickness of the plastic EDM electrode and its performances. It is found that the electroplated ABS plastic EDM RT electrode successfully performs the machining operation of D2 steel, and the results are comparable with a solid electrode. The study reveals that the RT electrode can be regarded as a viable tool for rough cutting or semi-finishing cut EDM functions. The experimental results are thoroughly discussed, examined, analyzed, and evaluated for the purpose of developing the appropriate form of the concept.

Ultra-fast sintered functionally graded Fe/W composites for the first wall of future fusion reactors

Aiming at the realisation of nuclear fusion reactors, the joining of W and steel parts is currently examined. Based on proposals to implement functionally graded steel/W materials (FGMs) in the joint to cope with thermal stresses, the present contribution introduces a novel fabrication method for steel/W FGMs. Electro Discharge Sintering (EDS) was used to consolidate Fe/W powders within milliseconds at atmosphere. Due to the short process time, the formation of detrimental intermetallic Fe-W precipitates is limited compared to established fabrication methods.The current work first presents results of the Fe/W powder processing, then a feasibility study regarding the fabrication of homogeneous and graded Fe/W composites with W volume fractions of 0, 25, 50 and 75 % via EDS is presented. Lastly, the composites are characterised microstructurally, thermo-physically, and mechanically in detail.