Electro-discharge Machining Research Articles

Effect of Thermo-Physical Properties of the Tool Materials on the Electro-Discharge Machining Performance of Ti-6Al-4V and SS316 Work Piece Materials

Electro-discharge machining (EDM) is a useful non-conventional machining operation frequently applied to make different complex geometries in any conducting material. The objectives of the present paper are to study the effect of a variation of thermo-physical properties (TPP) of three different tool materials on EDM performances. The different performances compared in this paper are: material removal rate (MRR), tool-wear rate (TWR), surface roughness (SR), radial overcut (ROC), surface-crack density (SCD) and surface hardness. Two of the most widely used work piece materials, such as corrosion-resistant austenitic stainless steel (SS316) and high strength corrosion-resistance titanium alloy (Ti-6Al-4V), are machined with the help of three different tools by varying input current and maintaining constant pulse-on time, pulse-off time and flushing pressure. Microstructural studies of the tool tip surface after machining have also been carried out. It is found that among these three tool materials, the copper tool showed the best machining performance with respect to material removal rate, radial overcut, surface finish and surface-crack density. This work will help industry personnel to choose a suitable tool for a specific work piece material.

Performance analysis of EDM electrode manufactured by direct metal laser sintering during machining of titanium alloy (Ti6Al4V)

Recently, additive manufacturing based rapid tooling (RT) is gaining popularity in manufacturing industries because tool fabrication time and cost can be substantially reduced. In this regard, an experimental investigation is made to explore the machining performance of AlSi10Mg tool electrode manufactured through direct metal laser sintering and compared with commonly used copper and graphite electrodes in electro-discharge machining (EDM) of titanium alloy work piece. The influence of EDM variables on performance measures like material removal rate, tool wear rate, arithmetic mean surface roughness, surface crack density, white layer thickness and microhardness has been analyzed. The machined surface generated with the usage of different electrodes is inspected by scanning electron microscopy to study the surface integrity. It is observed that superior surface integrity can be attained utilizing AlSi10Mg DMLS electrode at lower setting of machining parameters. Energy dispersion X-ray spectroscopy analysis reveals that transfer of tool electrode elements onto the machined surface occurs along with increase in percentage of carbon and oxygen on the machined surface. From the X-ray diffraction analysis, it is found that metal carbides like titanium carbide and vanadium carbide are formed on the machined surface leading to increase in microhardness of the surface.

Performance analysis of electrode materials in electro discharge machining of monel K-500

The present work focusses on the electrical discharge machining (EDM) of Monel K 500 super alloy with different electrodes. The study’s objective is to examine the effects of process parameters and electrode materials (Cu, W-Cu, and graphite) in terms of surface quality, material removal rateand electrode wear. In this context, EDM experiments have been designed and performed using the L27 standard orthogonal array of the Taguchi method with a statistical approach. The outcomes of this study reveal that the current plays an important role to improve the EDM machining performance of Monel K 500. The surface quality is approximately 11.62% and 55.52%, respectively better when Monel K-500 alloy is machined with copper electrodes compared to those in W-Cu and graphite electrodes. Moreover, The W-Cu electrode’s wear is approximately 15.73% and 21.05%, respectively less than those of graphite and Cu electrodes in optimum processing conditions. Graphite electrodes are better than Cu and W-Cu electrodes in terms of material removal rate. The statistical results also show that the estimation equations developed to select the optimum production conditions to give high accuracy results.

Suitability of Eroded Particles from Die-Sink Electro Discharge Machining for Additive Manufacturing—Review, Characterization and Processing

In this bipartite study, waste products of die-sink electro discharge machining (die-sink EDM) are investigated. EDM is based on an erosive character of discharges leading to material removal and molten material congeals in the dielectric. The aim is to show a theoretical suitability of these particles for a further usage as a secondary, recycled material in additive manufacturing (AM). Due to the energy- and cost-intensive process of gas atomization for AM powders, there is a need for alternative concepts for particle generation. The first part deals with an intensive review of references from the literature regarding particle size and circularity using image analysis. Secondly, real waste streams were investigated after washing and cleaning processes for oil removal via laser diffraction, dynamic image analysis, SEM with energy dispersive X-ray spectroscopy (EDX) as well as optical emission spectroscopy (ICP OES), categorized within the literature and compared to commercial AM powders. In general, it could be shown that, in principle, recycled particles fulfill main requirements for an AM usage regarding size and shape. Reference powders show median particle sizes of 30 µm to 34 µm and circularities of 0.90 to 0.93, whereas eroded particles exhibit an x50 value of 27 µm and circularity of 0.90, too. However, chemical purity, mainly caused by carbon contamination (5.4 wt% in eroded powder compared to 0.4 wt% in reference powder), must be improved before printing via AM machines. Additionally, several separation techniques have to be applied to remove undesired elements (alumina).

INFLUENCE OF WEDM-TEXTURED TOOLS ON THE MACHINABILITY OF TITANIUM GRADE-23 ALLOY

This study has been carried out to understand and reveal the efficacy of using surface-textured tools in the dry turning of Ti grade-23 alloys. The textures have been fabricated nearer to the primary cutting edge (in the rake face) and the secondary cutting edge (in the flank face) of the tool. The method used for texture fabrication is a nonconventional machining technique, Wire Electro-discharge Machining (WEDM). Micro-grooves/channels have been fabricated in the tools (rake face and flank face). The study also aimed to reveal the influence of texture pattern as well as its position on the cutting edges. The rake face-textured tools had four varieties: vertically textured (VT-R), diagonally textured (DT-R), horizontally textured (HT-R) and cross-textured (CT-R). On the other hand, the flank face had three varieties: cross-textured (CT-F), horizontally textured (HT-F) and vertically textured (VT-F). The cutting performance was measured and compared among the aforementioned different textured tools and nontextured (NT) ones in terms of the forces ([Formula: see text], [Formula: see text] and [Formula: see text]), temperature, tool wear and chip morphology. The study revealed that the textured tools performed better and the VT-R tool performed the best followed by the DT-R and VT-F tools as compared to NT ones for the dry turning of Ti grade-23 alloys.

Field emission properties of tetrapod-shaped ZnO/TiN point light source with semicircle reflecting anode

A novel point light source composed of tetrapod-shaped ZnO/TiN (T-ZnO/TiN) cathode and semi-circular groove reflective anode is demonstrated. The T-ZnO/TiN cathode is fabricated on nickel wire by spraying T-ZnO NRs powder and subsequent sputtering of TiN film. Semicircular reflective anodes with different opening sizes were prepared by wire electro-discharge machine. The field-emission properties of point light sources could be dramatically enhanced under semicircle reflecting anode by decreasing the threshold field from 2.61 to 2.10 V/μm. The point light source of D1500 has an extremely high emission current density of 132.73 mA/cm2 at 3.53 V/μm. The value of Jmax is about 2.7 times to that of D3000 (∼47.89 mA/m2 at 4.18 V/μm). Experiments and ANSYS electric field simulation show that the combination of low work function hybrid cathode and semicircular reflective anode structure leads to the increase of local field concentration and the enhancement of field emission characteristics. As far as we know, this point light source with semicircular reflective anode is prepared and applied for the first time. The results show that the point light source structure proposed here can not only effectively reduce the threshold field, but also improve the emission current density and luminescence uniformity.

Experimental investigation and prediction modelling of slicing speed and surface roughness during wafer slicing using WEDM

To keep up with the rising demand for silicon solar cells in the photovoltaic sector, an alternative slicing method that can achieve high throughput with minimal waste is required. In recent research efforts, Wire electro-discharge machining (WEDM) has become the possible alternative method for slicing. The experimental investigation focuses on slicing monocrystalline silicon using the WEDM process with a brass wire electrode of 250 μm in diameter. The face-centered central composite design was employed for planning and conducting experiments. The investigational experiments were conducted with five different process parameters serving as inputs: peak current, wire tension, wire feed rate, pulse on and off time. The response parameter measured was the slicing speed and the surface roughness. Further, comparisons were made between different kernel functions in support vector regression (SVR) for the prediction modelling of slicing speed and surface roughness. The difficulty in prediction modelling can be attributed to the complexity of the WEDM process, which is caused by the involvement of various process parameters. The primary purpose of this work is to determine the best predictive kernel among the linear, polynomial, radial basis function (Rbf), and sigmoid kernel functions based on the experimental data. The predictive performance of different kernel functions was evaluated and compared. Grid search was used for the hyper tuning of the kernel parameters. The radial basis function produces R2 of 99.751% and 97.552%, MSE values of 0.00046 and 0.00079, RSME values of 0.0215 and 0.02814, MAE values of 0.01645 and 0.01894, and MAPE values of 1.2% and 0.9% for slicing speed and surface roughness. Support vector regression with radial basis function gives better results in comparison to other kernel functions, which concludes that support vector regression with radial basis function is well suited for the prediction of slicing speed and surface roughness.

Machinability characteristics of titanium diamond using EDM and its parametric optimization

ABSTRACT The current research aims at analyzing the machining performance measures of titanium diamond using electro-discharge machining (EDM) process. The selected control variables are peak current and pulse-on-time (Ton) while maintaining a 50% to 75% duty factor during experimental runs. The output responses considered for this operation are material removal rate (MRR), tool wear rate (TWR) and average surface roughness (Ra). A full factorial design (L16) has been employed to execute the current investigation. Analysis of variance along with overall evaluation criteria (OEC) is also carried out for determining the optimal input parametric combination. The work is further supported by mean effect plots and 3D performance plots for visual illustration of outputs. Analyzed results show that current has the most impact on MRR and Ra, while Ton has the most impact on TWR. The obtained results show MRR of 7.753 mg/min (highest), TWR of 0.02 mg/min (lowest) and Ra of 5.46 µm at the optimum parametric combination. Moreover, x-ray diffraction (XRD), scanning electron micrograph (SEM), and energy-dispersive x-ray (EDX) analysis also help in identifying different phases of material on machined work surface.

Masking in EDM for pattern generation on Al-6061 work surface

ABSTRACTElectro discharge machining (EDM) is the most preferred non-traditional method for generating complex-shaped geometric pattern required in industrial and automotive applications. The present study shows the complex-shaped pattern generation by EDM process using polyvinylchloride masking material. Powder metallurgical (PM) green compact tool made of tungsten and copper is utilised to make patterns on aluminium (Al) 6061 workpiece. The effects of contributing parameters i.e. compact load (CL), peak current (Ip) and pulse on-time (Ton) are investigated with respect to performance measures such as surface roughness (Ra) and edge deviation (ED). The selected parameters are optimised using particle swarm optimisation (PSO) technique to determine the optimal levels of CL, Ip and Ton for achieving minimum Ra and minimum ED. The minimum Ra of 5.30 µm and a minimum ED of 43.53 µm are measured at optimal settings of CL of 20 ton, Ip of 2 A, and Ton of 200 µs. Analysis of variance (ANOVA) shows that Ip contributes the most to achieve the lowest Ra, while CL contributes the most to achieve the lowest ED. On the pattern surface FESEM, XRD, and EDS investigations are performed to study the surface morphology and to confirm the transfer of tool particles.

Machinability Analysis of Composite Electrode Produced by Spark Plasma Sintering Process during Electro-Discharge Machining of Titanium Alloy

Machinability Analysis of Composite Electrode Produced by Spark Plasma Sintering Process during Electro-Discharge Machining of Titanium Alloy

Effect of grey relational optimization of process parameters on surface and tribological characteristics of annealed AISI P20 tool steel machined using wire EDM

AbstractTo increase the productivity and quality of the machined components, wire electro-discharge machine parameters such as cutting speed, kerf width, and surface roughness are often optimized. The Wire-electro discharge machining process generates a much higher temperature at the wire-work piece interface which can potentially change the metallurgical characteristics of the machined surface. This paper studies the changes in the tribology of surface and sub-surface of the workpiece due to the initial and optimized wire-electro discharge machine parametric setting using grey relational analysis while machining sub-cooled AISI P20 tool steel. It is concluded that the optimum parametric setting to obtain a better cutting speed, kerf width, and surface roughness using grey relational analysis, which improves the productivity and quality of the component, also produces a thicker recast layer. The wear test revealed that the surface machined with an optimized parametric setting gives higher wear resistance. Detailed scanning electron microscopy explains the characteristics of the recast layer and micro-hardness explains the surface hardenability of tool steel, which is a result of martensitic transformation through rapid cooling, formed heat affected zone, and increase in oxygen content on the surface. The wear test proved that the recast layer helps in improving the wear resistivity of tool steel. The methodology of the hardening of the surface and the sub-surface layer can strengthen the application of components.

A brief review on the status of machining technology of fir-tree slots on aero-engine turbine disk

The machining precision and its consistency of turbine disk fir-tree slots have a direct influence on the performance of aero-engine rotor components. However, the structural dimensions of fir-tree slot are small, and the cutting performance of materials is extremely poor, which lead to great difficulty in machining and very few available machining methods. With the application of new materials in the aero-engines, the machining precision and quality requirements of fir-tree slots are further improved. Therefore, many research achievements on the high-efficiency, high-quality and low-cost machining technology of turbine disk fir-tree slots have been obtained. By summarizing and classifying the machining methods of aero-engine turbine disk fir-tree slots, a brief review on the characteristics of different methods are presented in detail, which provide a reference for selecting the appropriate machining method of turbine disk fir-tree slots in the field of aviation manufacturing. Meanwhile, combined with the research and application status of machining technology of turbine disk fir-tree slots, it is presented that multi-process compound machining is an effective method to realize high-efficiency, high-quality and low-cost precision machining of turbine disk fir-tree slots, such as wire electro discharge machining (wire-EDM) and profiled grinding, wire electrochemical machining (wire-ECM) and profiled grinding, wire-EDM and broaching, milling and broaching.

Design and control of an x-y-θz parallel piezoelectric nanopositioning stage with a large moving platform

This paper introduces the design and control of a new type of x- y-θ z parallel piezoelectric nanopositioning stage. Using the spatial cross-distributed double parallel four-bar linkage (DPFL), the mirror symmetrically distributed driving unit and auxiliary unit are designed. Then, a parallel piezoelectric nanopositioning stage with a large moving platform and good guidance and decoupling performance are designed. The workspace and frequency response characteristics of the stage are analyzed based on the stiffness and dynamic models. To improve the static and dynamic characteristics of the stage, the structural size is optimized, and the optimization results are verified by Finite Element Analysis (FEA). To reduce the response time, hysteresis nonlinearity, and external disturbance of the stage, a compound controller combining a rate-dependent Prandtl–Ishlinskii (PI) hysteresis compensator and a proportional-integral controller is designed. Finally, the prototype of the stage is made by Wire Electro-Discharge Machining (WEDM) technology. The open-loop performance of the stage is tested experimentally. The results show that the maximum relative coupling error between x and y directions is less than 0.5%. Also, the experimental control results show that the designed compound controller has a fast response speed, good positioning, and tracking performance.

Oscillation of a transient bubble between two parallel plates with cylindrical bulges

The dynamic behavior of a transient bubble oscillating between two rigid flat plates with internally mounted cylindrical bulges is studied numerically using the finite volume-based open-source software OpenFOAM-V6. Three different bulge radii with constant height are considered and the results are compared with the case of bare walls (i.e., walls without bulges). The radii of the considered bulges are half, equal to and twice the initial radius of the bubble. Based on the local Mach number, the flow of the fluid inside the bubble (gas phase) is considered compressible, while the flow of the fluid outside the bubble (liquid phase) is incompressible. Both phases are viscous, non-isothermal and immiscible and there is no mass exchange between them. The results are given in terms of bubble shape, velocity vectors and pressure field. It was found that the presence of the bulges reduces the overall lifetime of the bubble comprising the expansion, collapse, split, rebound and toroidal stages. Of the three bulge diameters considered, if the bulge diameter is equal to the initial diameter of the bubble, the lifetime of the bubble will be longer. Besides, at all the stages of its lifetime, the bubble shape is affected by the bulge diameter due to the ensuing different pressure fields. The results of the present work may be potentially useful in such applications as electro discharge machining (EDM) and cardiovascular treatment.

Performance of an Electrode Topology for Alkaline Water Electrolysis Under Specific Operating Conditions

Channels were machined over the active area of a 316L stainless steel electrode, in vertical electrode position, with a width of 5 mm that is reduced to 1 mm and then widened again. For its construction, electro discharge machining was selected since it also allows obtaining different degrees of roughness, which can favor the detachment of bubbles to a larger quantity. Analysis of its performance was carried out at an initial operating temperature of 30 ° C and at seven different distances between electrodes, namely: 9.45; 7.45; 6.35; 5.80; 4.30; 2.80 and 2.45 in millimeters, in order to determine the one with the lowest energy consumption to produce a fixed amount of hydrogen. Results obtained from the evaluated distances show that as the distance between electrodes becomes smaller, so do the electrical and transport resistances. The percentage increase in the current density for the distances of 9.45 and 2.45 mm, with respect to the applied potential difference, shows that at 2.2 V, it is above 80% (in current density) and maintained, with small fluctuations throughout the range of applied voltages. Therefore, using the same amount of energy, a greater volume of hydrogen is obtained.

Reverse Engineering Algorithm for Cutting of Ruled Geometries by Wire

Abrasive wire cutting (AWC) and wire electric discharge machining (WEDM) are efficient and economical processes for the fabrication of precision parts from bulk material. Operating costs and manufacturing lead times are low compared to more general methods such as 5-axis CNC milling, turning, or electro-discharge machining. In this paper, an algorithm based on differential geometry in Euclidean space is proposed for reverse engineering of ruled geometries. The algorithm can determine whether a given geometry is producible by wire cutting, and can also derive the associated wire trajectories. Implementation is demonstrated by producing complex turbine blade geometries on 4-axis wire cutting machines with an overall shape accuracy of 20–40 μm peak-to-valley.

Primary research on influence of workpiece cooling on efficiency of Inconel’s 625 alloy elecrodischarge milling in carbon dioxide

Inconel alloys one of the most cost intensive materials to machine with conventional machining methods. It is connected with its mechanical properties, as well as low thermal conductivity and also high material losses during machining. An alternative to conventional machining is electrodischarge machining (EDM), which enables to machine all the materials which are conductors or semi-conductors regardless its chemical composition and mechanical properties. There are three main dielectric types which can be used for EDM machining. The eco-friendly are gaseous ones. It is still hard to use gaseous dielectrics in the industrial applications, however it seems that this dielectrics are the future. The main aim of this research was to determine an influence of EDM milling in carbon dioxide used as dielectric in two configurations – with and without external workpiece cooling with deionized water on the EDM technological parameters (material removal rate, electrode wear) as well as technological surface integrity and surface structure.

A Review on Machinability of Shape Memory Alloys Through Traditional and Non-Traditional Machining Processes: A Review

This review article offers consolidated knowledge on the subject of several traditional and non-traditional procedures that are taking place throughout the years to form shape memory alloys (SMAs). At the primary part of the review, the usage of several shape memory alloys was shown. The dialogue then continued towards numerous traditional techniques of operating followed by the obstacles in the running of SMAs utilizing traditional techniques of operating. Moreover, numerous non-traditional processes of operations such WJM (Water jet Machining), cryogenic, WEDM (Wire Electro Discharge Machining), EDM (Electro Discharge Machining), and electrochemical machining explored. As well, Numerous of outcomes reactions that may occur during the operation procedures have been emphasized such as material removal rate (MRR), rate of tool wear, surface roughness (SR), the surface integrity. A consolidated records of various academics and their findings on this issue has been evaluated. After all, the article has been concluded by suggesting a variety of key points seen throughout the review process.

Investigation of Workpiece and Tool Surface Quality in Electro Discharge Machining of Al 5083 Alloy Produced by Powder Metallurgy

Aluminum alloys are widely preferred in various fields such as aerospace, ship and automotive due to their lightness and relevant production cost. In this study, electro discharge technique was used in the processing of aluminum 5083 alloy (Al5083) produced by powder metallurgy method. The surface quality resulting from the experiments was investigated in terms of Ra, Rz and Rsm. Experimental studies were carried out according to Taguchi L9 orthogonal experimental design, using three different levels of discharge current, pulse on time and pulse off time parameters. As the discharge current increased, Ra and Rz increased, Rsm first decreased and then increased. As the pulse on time increased, Ra and Rz first increased and then decreased, and Rsm increased. When the pulse off time increased, Ra and Rz decreased and Rsm increased. As a result of the analysis of variance (ANOVA) performed to determine the effect rates of the variable parameters on the surface quality, the order of importance of the parameters was found to be discharge current, pulse off time and pulse on time. The effect of discharge current, which is the most effective parameter according to ANOVA, on Ra, Rz and Rsm was calculated as respectively 70.87%, 70.41% and 36.34%. Microscopic images taken from the tool (copper) and workpiece surface show that the craters and peaks formed by the spark effect are formed on both material surfaces.

Performance study of different EDM Electrode Materials for machining of honeycomb cavities of plastic injection molds

Electro Discharge Machining (EDM) is an extremely prominent machining process among newly developed non - traditional machining techniques for “difficult to machine” conducting materials such as heat treated tool steels, composites etc. In EDM, the material removal of the electrode is achieved through high frequency sparks between the tool and the work-piece immersed into the dielectric. The Material Removal Rate (MRR), Tool Wear Rate (TWR) and surface integrity are some of the important performance attributes of the EDM process. This is widely used in machining intricate cavities in Aluminum HPDC Dies, Tyre mold manufacturing and Plastic Injection mold manufacturing. In Plastic injection mold manufacturing, especially for machining narrow cavities of honeycomb structures, the tool wears faster and machining becomes costly. This study compares performance of three materials viz. Copper, Graphite and Copper impregnated Graphite used as EDM electrodes and evaluates their performances based in lower Tool Wear Rates (TWR)