Electrical Discharge Machining Electrode Research Articles

An experimental work on using conductive powder-filled polymer composite cast material as tool electrode in EDM

This paper introduces the composite tool electrodes made of electrical conductive powder-filled polyester resin matrix material, providing promise for the electrical discharge machining (EDM) process. The dendrite-shaped copper powder, graphite powder, and their mixture were used as conductive fillers. Six different types of composite electrodes, namely, plain copper-polyester, pressed copper-polyester, furnaced copper-polyester, plain copper-graphite-polyester, pressed copper-graphite-polyester, and furnaced copper-graphite-polyester were prepared. It is found experimentally that increasing v f improved workpiece material removal rate, tool wear rate, relative wear, and electrical conductivity of electrodes. The pressed copper-polyester electrodes were found to be promising in the ED finishing of workpieces at low machining current settings. The practical applicability of the proposed composite electrodes in the industry was also illustrated.

Development of a new electrode for micro-electrical discharge machining (EDM) using Ti(C,N)-based cermet

Ti(C,N)-based cermets were recently designed for tool applications as they offer enhanced interfacial strength. These cermets exhibit a typical core/rim microstructure, as found in conventional cermets. To determine the possibility of using these new cermets as electrodes for electrical discharge machining (EDM), Ti(C,N) with carbides, nitride, solid-solution carbonitride such as (Ti,W)(C,N), and Ni were milled together, and sintered to manufacture an electrode to drill a micro-hole in a stainless steel thin plate (SS304) using micro-EDM. A commercial WC (tungsten carbide) electrode was selected to compare its machining capability with that of the homemade cermet electrode. To ensure a fair comparison of cutting performance, the optimal machining conditions for commercial WC, cermet, and the homemade cermet electrode were obtained using the Taguchi method and Grey relational analysis. Experiments under Taguchi and Grey relational optimal conditions showed excellent machining performance using the new homemade cermet electrode.

RETRACTED ARTICLE: Development and application of copper–nickel zirconium diboride as EDM electrodes manufactured by selective laser sintering

The production of electrical discharge machining (EDM) electrodes by conventional machining processes can account for over 50 % of the total EDM process costs. The emerging additive manufacturing (AM) technologies provide the possibility of direct fabrication of EDM electrodes. Selective laser sintering (SLS) is an alternative AM technique because it has the possibility to reduce the tool-room lead time and total EDM costs. The main difficulty of manufacturing an EDM electrode using SLS is the selection of an appropriate material. This work investigated the direct production of EDM electrodes by means of the SLS using a newly developed non-conventional metal–matrix composite material composed of a metallic matrix (CuNi) and an advanced ceramic (ZrB2). The influence of important SLS parameters and material content on the densification behavior and porosity of the electrodes was investigated. EDM experiments were conducted to observe the electrodes behavior and performance. It was found that the ZrB2-CuNi electrodes could be successfully manufactured by SLS. Interlayer bonding and porosity are directly influenced by the layer thickness. Smaller layer thicknesses improved bonding between layers and decreased the porosity of the parts. The laser scan speed has a significant effect on the densification behavior. The scan line spacing affects the pore structure by means of overlapping. The surface morphology of the samples was not affected by varying the scan line spacing. The ZrB2-CuNi electrodes presented a much superior performance than SLS copper powder electrodes, but inferior to solid copper electrodes.

Selective laser sintering of Mo-CuNi composite to be used as EDM electrode

Purpose – This work is focused on the investigation of direct production of electrical discharge machining (EDM) electrodes through the selective laser sintering (SLS) technique using a new metal-matrix composite material made of molybdenum and a copper-nickel alloy (Mo-CuNi). The influence and optimization of the main SLS parameters on the densification behavior and porosity is experimentally studied. Additionally, EDM experiments are performed to evaluate the electrodes performance under different machining conditions. The paper aims to discuss these issues. Design/methodology/approach – The new EDM electrode material used was a powder system composed of Mo and pre-alloyed CuNi. A systematic experimental methodology was designed to evaluate the effects of layer thickness, laser scan speed and hatch distance. The densification behavior, porosity and surface morphology of the samples were analyzed through microstructural and surface analysis. EDM experiments were conducted under three different regimes in order to observe the electrodes behavior and performance. The results were compared with copper powder electrodes manufactured by SLS and solid copper electrodes EDMachined under the same conditions. Findings – The experimental results showed that the direct SLS manufacturing of composite electrodes is feasible and an adequate combination of parameters can produce parts with good quality. The laser scan speed has a great effect on the densification behavior of the samples, while the effect of hatch distance on the porosity is more visible when the overlapping degree is considered. The overlapping also had a significant effect on the surface morphology. The EDM results showed that the Mo-CuNi electrodes had superior performance to the copper powder electrodes made by SLS for all the EDM regimes applied, but inferior to those achieved with solid copper electrodes. Originality/value – Significant results on the direct SLS manufacturing of a new material which has a great technological potential to be used as an EDM electrode material are presented. Valuable guidelines are given in regard to the SLS optimization of Mo-CuNi material and its performance as an EDM electrode. This work also provides a systematic methodology designed to be applied to the SLS process to produce EDM electrodes.

Surface Quality Modification Using Powder Metallurgy Processed CuW Electrode During Electric Discharge Machining of Inconel 718

Use of powder metallurgy processed (PM) electrode in electrical discharge machining (EDM) has emerged as an alternate tooling option with a view to impart improved surface properties to the work surface. Preliminary investigation with CuW PM electrode using Taguchi method was done on Inconel 718 to obtain best parameter settings for higher the better surface roughness. In the present work surface micro hardness study and X-ray diffraction (XRD) analysis was performed on the machined surface at the best parameter setting and comparison was done with the surface machined using conventional copper electrode. It was observed that the micro hardness of the machined surface was improved from 380.9 HV of the base metal to 496.7 HV of the surface machined with powder metallurgy processed electrode. XRD analysis revealed the formation of Fe2W3C6 phase on the machined surface causing remarkable improvement in the surface micro hardness.

A study on the SLS manufacturing and experimenting of TiB2-CuNi EDM electrodes

Purpose – This work aims to investigate the direct production of electrical discharge machining (EDM) electrodes by means of the selective laser sintering (SLS) technique using a new non-conventional metal-matrix composite material (TiB2-CuNi). The influence and optimization of the main SLS parameters on the densification behavior and porosity is experimentally studied. EDM experiments are also performed to evaluate the electrodes performance. Design/methodology/approach – The new EDM electrode material used was a powder system composed of TiB2 and CuNi. Making use of a designed systematic experimental methodology, the effects of layer thickness, laser scan speed and scan line spacing were optimized, where aspects such as densification behavior, porosity and surface morphology of the samples were analyzed through microstructural and surface analysis. EDM experiments were conducted under three different regimes in order to observe the electrodes behavior and performance. The results were compared with copper powder electrodes manufactured by SLS and EDMachined under the same conditions. Findings – The experimental results showed that the direct SLS manufacturing of composite electrodes is feasible and promising. The laser scan speed has a high effect on the densification behavior of the samples, while the effect of scan line spacing on the porosity is more visible when the overlapping degree is considered. Surface morphology was not affected by the scan line spacing, whereas balling phenomenon was reported, regardless of the scan line spacing. The EDM results showed that the TiB2-CuNi electrodes had a much superior performance than the copper powder electrodes made by SLS, regardless of the EDM regime applied. Research limitations/implications – Generally, the machine tool itself promotes some restrictions to the SLS process optimization. It is normally attributed to the characteristics of the laser type and the amount of energy that can be delivered to the powder bed. The present investigation could not cover all the optimization potential involved with the studied material due to limitations of the SLS machine tool used. Originality/value – Significant results on the direct SLS manufacturing of a new non-conventional composite material, which has a great technological potential to be used as an EDM electrode material, are presented. Valuable guidelines are given in regard to the SLS optimization of TiB2-CuNi material and its performance as an EDM electrode. This work also provides a systematic methodology designed to be applied to the SLS process to produce EDM electrodes.

Development of Strip EDM

Electrical discharge machining (EDM) is a widespread machining method for the die and mold industry. This method can machine all conductive materials, including hard-to-cut metals, because the machining process uses electro-thermal energy without a cutting force. During EDM, discharge sparks remove not only the material of a workpiece but also the material of an electrode. This machining mechanism thereby causes electrode wear, which creates serious problems, including make-shape errors and low productivity. In order to overcome such problems, a new EDM method using a strip electrode (strip EDM) was developed in this study. Strip EDM uses a continuously applied strip electrode similar to the wire electrode in wire EDM. In the suggested strip-electrode method, a conductive strip moves on the electrode guide. The worn strip is removed, and a new one is supplied continuously. Therefore, the tool electrode acquires no wear during the machining process. This method uses a conductive strip that is made of brass. In the practical machining process, the strip EDM method was applied to EDM milling and EDM turning and their machining characteristics were compared with general EDM methods.

Performance and Microstructure of TiN/Cu EDM Electrodes

This paper is to explore the feasibility of TiN/Cu-based composite materials as electrical discharge machining (EDM) electrodes.The tool wear ratio (TWR) of EDM electrode directly reflects the machining precision. To reduce the tool wear ratio(TWR) of Cu electrode in the EDM processing, Inorganic mixture of different content of ceramic materials TiN powder and Cu powder are prepared , then pressed and sintered into EDM electrodes.Experimental results show that: in the six batchs of experiments, the tool wear ratio (TWR) of 35%TiN/Cu electrode is the least, which is about 4.98%, much less than that of commercial copper electrode . The microstructures of the TiN/Cu electrodes after electrical discharge machining (EDM) as well are analyzed in this paper.

Performance of sinking EDM electrodes made by selective laser sintering technique

Electrical discharge machining (EDM) is a nonconventional machining process widely applied for the manufacture of intricate shapes in hard materials which are not easily machined by conventional machining processes. The production of geometrically complex EDM electrodes is difficult, time consuming, and it can account for about 50 % of the total process costs. Selective laser sintering (SLS) can be an alternative technique to produce EDM electrodes in a faster way. This work conducted an experimental study on the performance of EDM electrodes made by SLS using pure copper, bronze–nickel alloy, copper/bronze–nickel alloy, and steel alloy powders. Important EDM performance measures such as material removal rate and volumetric relative wear were investigated and discussed for finishing, semifinish, and roughing regimes. This work contributes with an insight into the production of EDM electrodes via selective laser sintering, as an alternative technique to conventional machining processes, as well as to evaluate the performance of the electrodes, and also provide directions for future research on this field.

Effect of Electrode Material on Electrical Discharge Machining of DIN 1.2379 and DIN 1.2080 Surface

Electrical Discharge Machining (EDM) is used in cutting special steel accurately; in this paper the effect of electrode material will be studied to avoid the surface cracks. Two grades of tool steels are chosen as test materials, DIN 1.2080 and DIN 1.2379 they are a high carbon, high chromium alloy tool steels with excellent resistance to wear and abrasion four types of EDM electrode material has been chosen, Dura graph 11, Dura graph 15, Poco graphite “EDM-C 3”, and copper electrodes.

Copper-chromium alloy as a superior electrode material for electrical discharge machining of die steels

Electrical discharge machining (EDM) is widely used for the machining of accurate profiles in dies and press tools which have been previously hardened. Electrode material properties significantly affect the output process parameters. This paper investigates the performance of copper-chromium alloy with copper and brass as EDM electrode materials. It has been found that copper-chromium alloy gives higher material removal rate, superior surface finish, better micro-hardness and least overcut (good dimensional accuracy). At the same time, its tool wear rate is lower which results in better accuracy and trueness of the machined profiles. Scanning electron microscope (SEM) image after machining with this electrode material shows a smoother surface with smaller asperities. Energy dispersive spectroscopy (EDS) analysis of the machined surfaces reveals the presence of electrode constituents and indicates surface alloying by EDM process.

An overview of technology and research in electrode design and manufacturing in sinking electrical discharge machining

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes, based on thermoelectric energy between the workpiece and an electrode. In this process, the material is removed electro thermally by a series of successive discrete discharges between two electrically conductive objects, i.e., the electrode and the workpiece. The performance of the process, to a large extent, depends on the material, design and manufacturing method of the electrodes. Electrode design and method of its manufacturing also affect on the cost of electrode. Researchers have explored a number of ways to improve electrode design and devised various ways of manufacturing. The paper reports a review on the research relating to EDM electrode design and its manufacturing for improving and optimizing performance measures and reducing time and cost of manufacturing. The final part of the paper discusses these developments and outlines the trends for future research work.

Effect of Carbon Nanotube (CNT) Size on Wear Properties of Cu-Based CNT Composite Electrodes in Electrical Discharge Machining

The effect of carbon nanotube (CNT) size on the wear properties of Cu-based CNT composite electrode in electrical discharge machining (EDM) was studied. Cu-based CNT electrodes were fabricated by electroplating using a copper sulfate plating bath containing three kinds of CNTs. EDM was performed on stainless steel to evaluate the wear properties of the electrodes. Single pulse discharge was performed to evaluate the craters generated on the electrode surface. The wear ratios of Cu-based CNT composite electrodes decreased by 50-72% in relation to those of electrolytic Cu electrodes. The wear resistance of the composite electrodes was dependent on CNT size. It increased as the length and thickness of CNTs increased. The mechanisms of wear resistance in Cu-based CNT composite electrodes are discussed through observation and analysis of craters formed by single pulse discharge. The diameters of the craters are almost identical and largely independent of the size and presence of CNTs, indicating that CNT addition does not improve the thermal conductivities of the electrodes. Hence, the increase in wear resistance is independent of thermal conductivity. Exposed CNTs observed in craters on electrodes containing large CNTs with high wear-resistance properties do not decrease in diameter via electrical discharge, indicating that large CNTs can be resistant to pyrolysis at the melting points for Cu and Fe. It is suggested that the carbon layer with exposed CNTs on the electrode surface prevents the electrode from spark erosion in a manner identical to that of turbostratic carbon.

Optimisation of electrical discharge machining process with CuW powder metallurgy electrode using grey relation theory

In this paper, an attempt has been made to correlate the usefulness of powder metallurgy (PM) electrodes in electrical discharge machining (EDM). This paper explains the same with the help of experimentation on AISID2 steel in kerosene with CuW (25% Cu and 75% W) PM electrode. An L18 orthogonal array was used to identify the effect of process parameters (viz. electrode material, duty cycle, flushing pressure and current) on the performance characteristics i.e., material removal rate surface roughness and surface hardness. A grey relation grade obtained from the grey relation analysis is used to solve the EDM process with multiple performance characteristics. Experimental results have shown that electric discharge machining process performance can be improved efficiently through this approach. It is found that copper tungsten PM electrode gives better multi-objective performance than conventional copper electrode.

Design and Implementation of Automatic Discharge Gap Controller for a Curved Hole Creating Microrobot with an Electrical Discharge Machining Function

This study deals with the development of a mechanism which can autonomously and automatically control the discharge gap for achieving electrical discharge machining (EDM) in an almost isolated space. This is so that a microrobot equipped with the mechanism can create a long, complicated curved hole, a hole that could not be formed by conventional machining methods. Holes formed by conventional machining methods are generally straight, so pipelines built in a variety of mechanical apparatuses consist of straight or polygonal lines. Such dearth of variety in realizable hole shapes can sometimes cause fundamental problems. A typical example of the problems appears in the design and production of water channels, i.e., pipelines built in metal molds to achieve appropriate thermal controls in molding processes. Specifically, the low variety of hole shapes prevents the shapes and positions of water channels from being optimized for the best thermal control in molding. Therefore, the development of a new method for machining curved holes has been needed. To meet this needed, we have conceived a method of machining curved holes by employing a microrobot that can perform EDM. A long, complicated curved hole can be created by making the microrobot perform stable EDM while moving along a long, complicated, curved trajectory in a workpiece. In order to realize this concept, the microrobot must have the capability to autonomously and automatically control the discharge gap in such an almost isolated space as the bottom or end of a curved hole. Accordingly, this study devises a new mechanism to give the microrobot this capability, and it calls the mechanism the “automatic discharge gap controller” (ADGC). The main components of ADGC are an electrode and power supply for EDM and a bidirectional actuator in which shape memory alloy (SMA) is employed. The results obtained from the experiments using a prototype of the ADGC prove that the ADGC has the capability of performing stable EDM by controlling the discharge gap autonomously and automatically without any other actuators.

Direct Measurement of Electrode Movement During Electrical Discharge Machining by Means of Automatic Discharge Gap Controller

This study deals with the development of a new method of directly measuring the movement of an electrode during normal electrical discharge machining (EDM) and the movement of an electrode during EDM by means of an automatic discharge gap controller (ADGC) devised by our research group. The ADGC, which mainly consists of a bidirectional actuator using a shape memory alloy (SMA) and an electrode and power supply for EDM, can sustain stable EDMby autonomously and automatically controlling the position of the electrode to keep the discharge gap appropriate. However, the movement of the electrode being controlled by the ADGC cannot be directly measured due to itsminute, high-speed, vibration-like movements inside the working fluid during EDM. This means that there is no way to prove that the ADGC actually controls the position of the electrode so as to maintain a suitable discharge gap for continuing stable EDM. This also means that there is no way to evaluate the movement of the electrode quantitatively and to design or optimize the structure of an ADGC so as to give the ADGC the desired or best performance. Therefore, a method to directlymeasure the electrodemovement by an ADGC is devised in this study. The results obtained in the measurement experiments using this method of measurement prove that the ADGC actually moves its electrode to achieve stable EDM, and they allow the movement of the electrode to be evaluated quantitatively.

Cooling Effect on Electrode and Process Parameters in EDM

In electrical discharge machining (EDM), material is removed by a series of electrical sparks that develops a temperature in the range 8, 000°C–12, 000°C between the electrode and the workpiece. Due to the high temperature of the sparks, the workpiece is melted and vaporized. At the same time, the electrode material is also eroded by melting and vaporization. This erosion of the electrode is termed as electrode wear (EW). The EW process is similar to the material removal mechanism as the electrode and the workpiece are considered as a set of electrodes in EDM. Due to EW, electrodes lose their dimensions resulting in inaccuracy of the cavity formed by EDM. This paper reports on the study of the effect of electrode cooling during the EDM of titanium alloy (Ti-6Al-4 V). Investigation on the effect of electrode cooling on electrode wear was carried out. Current, pulse on-time, pause off-time, and gap voltage were considered as the machining parameters while EW is the response. Analysis of the influence of electrode cooling on the response has been carried out, and it was possible to reduce EW by 27% using this method.

Novel Jump Control for Debris Processes of Electrical Discharge Machining with Direct-Drive Spindle

Owing to its low removal rate and debris ejection nature, EDM is a very slow machining process. A novel jump motion control for electrode in electrical discharge machining (EDM) equipped with dual linear motors (LmEDM) was proposed to release this debris efficiency point. The direct drive EDM and a novel pulse discriminator were developed. By introducing the discriminator to count effective discharge pulses, an EDM jump control was proposed. Experiments for verification of the EDM efficiency were conducted for 35 mm deep and thin EDM processes with 2 mm thin platelet. EDM efficiency of proposed jump control is verified to be four times over the traditional EDM.

Performance analysis of EDM electrode fabricated by localized electrochemical deposition for micro-machining of stainless steel

Electrical discharge machining (EDM) is an important and widely used process for the fabrication of complex three-dimensional structure of micro-tools, micro-components, and parts with micro-feature. It allows high precision, low setup cost, large freedom of design, and good surface quality. However, in order to produce different varieties of high-accuracy structures on machine, microelectrode fabrication is necessary so as to reduce the clamping error which is one of the biggest challenges in the field of micro-EDM. In this study, it has been shown that localized electrochemical deposition (LECD) is one of the simplest, inexpensive, and damage-free ways to fabricate complex-shaped electrodes for micro-EDM compared to other conventional electrode fabrication processes. In this study, electrode was fabricated with the help of a non-conductive mask which was placed between the anode and the cathode where the cathode was placed above the anode and mask and the system was immersed in a plating solution of acidified copper sulfate. The micro-EDM was carried out by the deposited electrode without changing or removing its orientation. The performance of LECD electrode was evaluated in this study by micro-holes fabrication on high melting point material such as stainless steel in terms of the material removal rate, tool relative wear ratio, and dimensional accuracy. Finally, the performance of the LECD electrode was also evaluated by a comparative study with a circular EDM electrode for fabrication of complex three-dimensional structure.

Reducing Electrode Wear Using Cryogenic Cooling during Electrical Discharge Machining

In electrical discharge machining (EDM), material is removed by a series of electrical discharge between the electrode (tool) and the workpiece that develops a temperature of about 8,0000C to 12,0000C. Due to high temperature of the sparks, work material is melted and vapourized, at the same time the electrode material is also eroded by melting and vapourization. Electrodes wear (EW) process is quite similar to the material removal mechanism as the electrode and the workpiece are considered as a set of electrode in EDM. In the present study effort has been made to reduce EW by cooling, using liquid nitrogen during the EDM of titanium alloy. Investigation on the effect of cooling on electrode wear (EW), material removal rate (MRR) and surface roughness (Ra) of the workpiece was carried out. Current (I), pulse on-time (ton), pause off-time (toff) and voltage (v) were considered as the machining parameters. Design of experiment (DOE) was used to design the experimental works. Cooling of electrode by this technique reduced the melting and vapourization of electrode material and enhances electrode life. It was possible to reduce EW up to 27% by applying this technique while MRR and Ra were improved by 18% and 8% respectively.