Wire Electrical Discharge Machining Performance Research Articles

Integrating experimental modeling techniques with the Pareto search algorithm for multiobjective optimization in the WEDM of Inconel 718

Inconel 718 is a superalloy with a high nickel content that is widely used in applications requiring solid mechanical behavior and resistance to oxidation and corrosion at high temperatures. This alloy has numerous applications in manufacturing steam turbine and jet aircraft interiors, aviation sector manifolds, and rotary spindles. It can be classified as a difficult-to-cut material unsuitable for traditional machining. The purpose of this paper is to develop prediction models for a wire electrical discharge machining (WEDM) process using response surface methodology (RSM), artificial neural networks (ANN), and adaptive neuro-fuzzy inference systems (ANFIS) and to determine which model is better at making accurate predictions. Pulse_ontime, pulse_offtime, servo voltage, flushing pressure, and wire feed were considered the main factors affecting volumetric material removal rate (VMRR) and arithmetic surface roughness (Ra), which were evaluated as WEDM performance characteristics. I-optimal design made with a computer algorithm was employed to develop experimental models. The results reveal that the wire feed and pulse_ontime were the most vital factors influencing VMRR, respectively, and the most significant factor influencing Ra is the pulse_ontime. The total percentage error of the three models demonstrated that the ANN and ANFIS models are more reliable and accurate than the RSM mathematical model. Finally, multiobjective optimization using the Pareto search algorithm was used to optimize mathematical, ANN, and ANFIS models to determine the optimum WEDM process parameters for machining Inconel 718 superalloy.

Response Surface Modelling and Effective Application of Adaptive Neuro-Fuzzy Inference System to Analyze Surface Roughness of Al/Gr/Cp5 MMC Machined using WEDM

ABSTRACT This paper presents an investigation of wire electrical discharge machining (WEDM) of new fabricated aluminium base composite with 5% graphite by weight, i.e., Al/Gr/Cp5. The new fabricated metal matrix composite (MMC) has a complete application in space, defence, automobile, and other concerned metal industries. In this work, adaptive neuro-fuzzy inference system (ANFIS) and the response surface method (RSM) were selected for the analysis and modelling purposes. ANFIS is a soft computing technique used in nonlinear data training. Taguchi’s L27 plan was employed to conduct the experiments. The process parameters such as pulse-on time (PON), pulse-off time (POFF), a feed rate of wire (FRW) and the input current (IC) were selected for the experimentation. Based on the experimental findings, PON is identified as the most dominant parameter and the input current. WEDM performance was measured in terms of surface roughness (SR). For the optimised (minimum) surface roughness of 1.8625 microns, the best set of process parameters was PON (108 μs), POFF (52 μs), FRW (4 m/min) and the input current (12 Amp). ANFIS-predicted results were compared with the experimental results. An acceptable agreement is observed with the high value of the correlation coefficient (R2 = 0.9624). The soft computing technique, like ANFIS-RSM, shows a good competency and reliability for the presented work.

Improving reciprocating traveling WEDM performance by a new adaptive servo feedrate control system

With variations in gap discharge state or workpiece height, the servo feedrate of wire electrical discharge machining (WEDM) often fluctuates, and the machining process easily becomes unstable, thereby resulting in a decrease in material removal rate or an increase in risk of unexpected wire breakage. With developments of ISO-pulse discharge pulse power supplies and reciprocating traveling WEDM, a precise discharge state monitoring system for the servo federate control system is required. In this paper, with each single discharge pulse being precisely classified and counted, more accurate feedback information can be provided to the servo feedrate control system. Then a new adaptive servo feedrate control system with a self-tuning regulator and a variable gain linear proportional controller has been proposed to improve the material removal rate and control performance. The scheme of an adaptive servo feedrate control system is analyzed. It is found that the new adaptive servo feedrate control system by using a variable gain linear proportional component has a better control performance. By adjusting servo parameters, the discharge ratios are regulated, and the servo feedrate control system can keep the gap discharge state stable. Experimental results show that the material removal rate can be improved significantly by up to 19% with the new adaptive servo feedrate control system, without sacrificing the surface quality.

Wire EDM process parameter optimization for D2 steel

Wire electrical discharge machining (WEDM) is most suited for machining conductive materials when precision is required. There are a large number of input control parameters that govern the WEDM performance. Thus, it becomes essential to optimize process control parameters to achieve optimal results. In the present paper process parameter optimization using Taguchi quality design concept of L16 orthogonal array for the wire-cut electrical discharge machining of D2 steel is done. Four process control parameters, namely wire speed, gap voltage, flushing pressure, and current, are analyzed for two response parameters viz surface roughness and material removal rate (MRR). It is found that MRR during WEDM have a predominant impact of current on it, while flushing pressure has the least impact on MRR. Whereas, surface roughness is most effected by wire speed during WEDM and gap voltage has the least impact on surface roughness of D2 steel workpiece during WEDM process.

WEDM process parameter optimization of Al-Al3Fe in-situ composites

This experimental investigation aims to optimize wire electrical discharge machining (WEDM) process parameters of Al-Al3Fe in-situ composites prepared by reactive stir casting route. Following a robust design lay-out of Taguchi L27 array, WEDM tests have been carried out by varying one material parameter namely, volume percent of reinforcement (VR), and three machining parameters namely, pulse-on time (Ton), servo voltage (Sv) and peak current (Ip); whereas, the material removal rate (MRR) and surface roughness (SR) are considered as output responses. The influences of input parameters on MRR and SR are statistically quantified by ANOVA. Significant process parameters are identified as Ton (69%), Sv (19%) and Ip (7.74%) on MRR; while only Ton (39%) on SR. MRR and SR values are found to be minimum for 20 vol% Al3Fe reinforced composite. Predictive models are generated considering full quadratic response surface equations and validated through several confirmatory tests. Besides, the desirability approach has been adopted for multi-response optimization of MRR and SR; the obtained solutions are affirmed by conducting new tests, and the related error is estimated at less than ±10%. Considering the robustness of the generated models, these models could be used for predicting WEDM performance of in-situ transitional metal tri-aluminides reinforced Al-matrix composites.

Influence of Nozzle Jet Flushing on Working Fluid Flow and Wire Electrode in Trim-cut WEDM

In wire electrical discharge machining (WEDM) process, smooth exclusion of debris and bubble generated in the narrow gap is important to keep stable machining performance. Conventionally, the debris exclusion has been carried out by jet flushing of working fluid from upper and lower nozzles. This study aims to clarify the effects of jet flushing on WEDM characteristics by utilizing computational fluid dynamics (CFD) analysis. Then, the fluid flow fields and debris exclusion in the machined kerf during 1st-cut WEDM have been clarified so far. On the other hand, a trim cut is carried out after 1st-cut WEDM. The effects of jet flushing with smaller flow rate have not been investigated, since the geometrical workpiece shape around the wire is quite different from that in 1st-cut. In this study, the flow field of working fluid around the discharging site by jet flushing using nozzles and the influence on wire behavior were analytically investigated by CFD analysis in trim-cut situation. Also, the accuracy of CFD analysis results was verified by comparison with high-speed observation of actual fluid flow in WEDM. Furthermore, the wire deflection in trim-cut situation was simulated by using a structural analysis with considering pressure distribution acting on the wire surface obtained by the CFD analysis. The analytical results showed that the flow field around the wire periodically fluctuated regardless of flow rates with jet flushing when the workpiece thickness is relatively small. The wire deflection shape also changed due to the periodic fluctuation of fluid flow field around the wire. Furthermore, in order to investigate the influence on the trim-cut WEDM performance, the surface roughness of trimmed surface was measured for various workpiece thicknesses. It was found that the surface roughness become larger by the periodic fluctuation when the workpiece thickness is relatively thin.

Real-Time Wire EDM Tool Simulation Enabled by Discharge Location Tracker

In Wire Electrical Discharge Machining (WEDM), one of the most limiting factors for productivity, especially during rough cutting, is the wire breakage. Root causes of wire breakage are widely investigated in the literature and three main causes have been identified: mechanical rupture, excessive thermal load on wire and discharges concentration. Since the wire breakage is essentially the limiting factor for WEDM performance, the capability to safely approach the wire electrode exploitation limits is crucial for high performance and high efficiency WEDM. This paper describes a real-time, in-process, Finite Elements Model (FEM) simulation of the tool electrode in WEDM. Using the Discharge Location Tracker (DLT), position and energy of each discharge is known; allowing real-time realistic simulation of the wire electrode thermo-mechanical status. Based on the single discharges crater volume and on the wire unwinding speed, the wire electrode wear is simulated and its radius as a function of the vertical coordinate r(z) is calculated. Then, the thermal equilibrium of the wire is computed using a FEM algorithm, taking in consideration the real-time wear and transport of the wire for Joule dissipation, thermal convection and thermal diffusion. Moreover, the wire heating is also calculated in real-time based on the single discharge position and energy. The numerical model, coupled with the DLT sensor, allows real-time monitoring of the wire electrode thermo-mechanical state during machining.

Influence of machining parameters on wire electrical discharge machining performance of reduced graphene oxide/magnesium composite and its surface integrity characteristics

Taguchi coupled grey relation analysis is adopted to study the effects of machining parameters of Wire Electrical-Discharge Machining (WEDM) on magnesium metal matrix composite reinforced with Reduced Graphene Oxide(r-GO). An optimal combination of process parameter was expected to be finalized in this research to attain maximum Material Removal Rate (MRR) with a minimal surface roughness (Ra) value. The composite was fabricated through solvent based powder metallurgy route for varying percentage of r-GO. Experimental combination for WEDM of developed composite specimens were finalized to be L27 orthogonal array (OA) using Taguchi's method mainly based on the control factors namely reinforcement weight percentage (wt.%), pulse ON time (P1), pulse OFF time (P2) and wire feed rate (Wfd). ANOVA results revealed that wt.% and P1 are the most influencing parameters for MRR and Ra. Outputs scaleup that the developed regression model augments well with the experimental values. Using grey relation analysis (GRA) the optimal parameter was set and the final results obtained based on the optimal combination was found to be with a maximum MRR (18.38 mm3/min) and minimum Ra (3.29 μm). Traces of intermetallic formation are identified over the machined surface due to the action of machining parameters.

Study of surface integrity and machining performance during main/rough cut and trim/finish cut mode of WEDM on Ti–6Al–4V: effects of wire material

Due to increased demand of dimensional accuracy and high precision of manufactured parts, wire electrical discharge machining (WEDM) became very popular, especially for ‘difficult-to-cut’ materials like titanium alloys. Grade 5 Ti alloy (Ti–6Al–4V) has enormous application in aerospace and biomedical fields. WEDM performance of Ti–6Al–4V is somewhat restricted due to its poor thermal conductivity, formation of hard and brittle carbide-/oxide-rich layer and often surface cracking which affect fatigue performance of the part product. Therefore, multi-cut strategy is adapted to mitigate machining-induced defects. The multi-cut mode consists of one main/rough cut followed by a number of trim/finish cuts. Aspects of surface integrity of the WEDMed Ti–6Al–4V obtained in different modes of cut are delineated in this reporting. Three slots are produced: (1) main cut; (2) main cut followed by one trim cut; and (3) main cut followed by two trim cuts using uncoated brass wire and zinc-coated brass wire, respectively. Surface morphology along with topographical features including roughness average, crack density, recast layer thickness, material immigration, residual stress and micro-indentation hardness is studied. Results obtained thereof are analysed with relevance to kerf width, material removal rate and wire wear.

Investigation on a novel surface microstructure wire electrode for improving machining efficiency and surface quality in WEDM

Wire electrode is one of the key factors in determining the machining performance of wire electrical discharge machining (WEDM), and developing high-performance wire electrode is an effective method for meeting the ever-increasing requirement of modern manufacturing industries. In this paper, a novel surface microstructure wire electrode (SMWE) is proposed to enhance the performance of WEDM. Experiment data demonstrate that, compared with brass wire electrode and zinc-coated wire electrode, SMWE increases machining efficiency by 23.9–77.8% for Inconel 718 and 14.8–38.6% for Ti6Al4V, and decreases surface roughness by 11–20% for Inconel 718 and 7–10% for Ti6Al4V, respectively. Besides, SMWE can also obtain smoother surface topography, thinner recast layer, and narrower surface cracks. Furthermore, the improvement mechanism of SMWE is revealed from different aspects. It can be found that SMWE can shorten discharge gap breaking downtime, avoid the occurrence of sparks at the same point, and promote more removed debris and heat energy to be brought out. In a word, this proposed SMWE has good popularization value for application in practical industries, and this study provides a new idea for developing high-performance wire electrode.

WEDM Performance of Ti-6Al-4V: Emphasis on Multi-Cut Strategy, Effects of Electrode Wire

Abstract In the present work, machinability of Ti-6Al-4V was studied during Wire Electrical Discharge Machining (WEDM) in consideration with multi-cut strategy. Multi-cut strategy includes one main/rough cut followed by a number of finish/trim cut. Machining performance was assessed in purview of Kerf width, Material Removal Rate (MRR), phenomena of wire wear, and finally, surface integrity of the end product. Apart from surface morphology, topographical studies were made which included surface roughness, surface crack density, white layer thickness, element transfer, metallographic features. Performance of electrode wire (uncoated brass and zinc coated brass wire) in relation to different modes of cut was compared in the context of WEDM of Ti-6Al-4V.

Modeling and prediction of WEDM performance parameters for Al/SiCp MMC using dimensional analysis and artificial neural network

In the present work, The CNC wire electrical discharge machining (WEDM) of Al 2124 SiCp (0,15,20) Metal Matrix Composite (MMC) is analysed by using dimensional analysis approach (DA) & artificial neural network (ANN). The models are formulated to correlate the independent parameters such as pulse on time, pulse off time, wire feed rate, current, voltage, thermal conductivity of the work piece material, coefficient of thermal expansion, density and the wire tension with the dependent parameters surface roughness and the material removal rate through design of experiments (DOE) plan. From the experimental findings, it has been observed that the pulse on time, thermal conductivity, coefficient of thermal expansion, wire feed rate and the wire tension are the most influencing parameters. In order to find out the accuracy of the formulated DA and ANN models, correlation coefficient (R2) was calculated. From the R2 values, it was clear that both DA and ANN approaches are competent to predict the surface roughness and the material removal rate. In addition, the models formulated by using ANN approach were found to be more reliable than the DA approach. The higher values of R2 (99.9910%) and lower value of various error based parameters shows the adequacy and reliability of the DA and ANN models. Comparative study of DA and ANN models disclosed the accuracy of ANN models hence recommended.

Magnetic-assisted method and multi-objective optimization for improving the machining characteristics of WEDM in trim cutting magnetic material

In wire electrical discharge machining (WEDM), increasing the machining characteristics is always a research hot spot. Now, magnetic-assisted method cannot directly improve the performance of WEDM during machining magnetic material. In addition, due to the defects of convergence precision, convergence speed, global optimization, and subjectivity, the application of individual parameter optimization algorithm is limited. In order to address these problems, this paper proposes magnetic-assisted method and modified non-dominated neighbor immune algorithm to ameliorate the performance of WEDM in trim cutting magnetic material. Firstly, the force analysis of debris and the analysis of discharge current waveform are carried out to clarify what setting condition of the magnetic field generator is proper. It is indicated that the magnetic-assisted method maybe improves the machining characteristics of WEDM when the Lorentz force has the same direction with dielectric flashing force during trim cutting magnetic material. Additionally, a set of trim cutting Taguchi experiment is accomplished to investigate the effect of magnetic-assisted method on material remove rate (MRR), surface roughness (SR), and recast layer thickness (RLT). Thereinto, it can be found that the machining characteristics of WEDM are obviously improved by magnetic-assisted method. More specifically, under magnetic-assisted method, MRR, SR, and RLT are improved by an average of 18.45, 17.86, and 17%, respectively. Then, on the basis of game theory, the modified non-dominated neighbor immune algorithm (NNIA) is proposed to select best process parameters for further increasing the machining characteristics of magnetic-assisted WEDM (MA-WEDM). Eventually, the comparative results of three algorithms and verification experiment demonstrate that this modified NNIA exhibits better optimization performance than NSGA-II and NNIA. Specifically, by modified NNIA, the largest increase of MRR and the greatest decrease of SR and RLT are 22.37, 44.59, and 15.07%, respectively.

Analysis and Optimization of WEDM Performance Characteristics of Inconel 706 for Aerospace Application

Wire Electrical Discharge Machining (WEDM) has established itself for manufacturing of precise and complex shape components for aerospace application due to the high quality requirement of aerospace components such as normal residual stress, no cracks, no recast layer, no porosity; still there is a need to optimize the control parameter settings and evaluate the performance characteristics of the WEDM process. The experiments have been conducted on Inconel 706 which is a newly-developed superalloy specially for aircraft application. A hybrid approach has been used to optimize the material removal rate (MRR) as well as surface roughness (SR) and significant control parameters have been identified using analysis of variance (ANOVA). Microstructure analysis revealed the formation of microglobules, melted debris and microholes on the machined surface, but no microcrack was detected due to the high toughness of the alloy. Energy dispersive X-ray spectroscopy (EDAX) has been carried out to study the metallurgical changes in the WED machined surface. The topography analysis of the curved surface revealed the best surface quality of the machined component at low pulse on time and high pulse off time. A thick recast layer of 39.6 µm was observed at high pulse on time and low servo voltage. Microhardness of the machined surface was changed up to a depth of 70 µm due to cyclic thermal loading during the WEDM process.

Proposing a new performance index to identify the effect of spark energy and pulse frequency simultaneously to achieve high machining performance in WEDM

Wire electrical discharge machining (WEDM) is a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks). WEDM demands high cutting rate and high quality to improve machining performance for manufacturing hard materials. The machining performance of computer-controlled WEDM is directly dependent on spark energy and pulse frequency parameters including discharge voltage, peak current, pulse duration, and charging time. In this paper, a new performance index to measure the effects of spark energy and pulse frequency on machining performance is proposed. Moreover, the effects of electric process parameters on performance measures including cutting speed, surface roughness, and white layer thickness are introduced.

Effect of wire diameter on surface integrity of wire electrical discharge machined Inconel 706 for gas turbine application

Inconel 706 superalloy has established itself in the field of gas turbine industry because of its easy fabricability combined with high mechanical strength. Due to its high stress rupture and tensile yield strength, conventional machining of this superalloy exhibits poor surface and low dimensional accuracy of the machined components. It is well known that most of the gas turbine components include complex shaped profile with high precision and hence, wire electrical discharge machining (WEDM) of Inconel 706 has been performed to achieve the feasibility in manufacturing of complex shaped components for gas turbine application. In the current investigation, the effect of wire diameter on WEDM performance characteristics such as cutting speed, surface roughness, surface topography, recast layer formation, microhardness, microstructural and metallurgical changes have been evaluated. It was investigated that smaller diameter wire is advantageous over the larger diameter wire since it improves productivity as well as surface quality of the machined components under the same settings of control parameters. In addition, smaller diameter wire has shown comparatively lower recast layer thickness, minimum hardness alteration and shorter manufacturing time. The XRD result has confirmed the presence of residual stress within WED machined component.

Optimizing machining parameters of wire-EDM process to cut Al7075/SiCp composites using an integrated statistical approach

Metal matrix composites (MMCs) as advanced materials, while producing the components with high dimensional accuracy and intricate shapes, are more complex and cost effective for machining than conventional alloys. It is due to the presence of discontinuously distributed hard ceramic with the MMCs and involvement of a large number of machining control variables. However, determination of optimal machining conditions helps the process engineer to make the process efficient and effective. In the present investigation a novel hybrid multi-response optimization approach is proposed to derive the economic machining conditions for MMCs. This hybrid approach integrates the concepts of grey relational analysis (GRA), principal component analysis (PCA) and Taguchi method (TM) to derive the optimal machining conditions. The machining experiments are planned to machine Al7075/SiCp MMCs using wire-electrical discharge machining (WEDM) process. SiC particulate size and its weight percentage are explicitly considered here as the process variables along with the WEDM input variables. The derived optimal process responses are confirmed by the experimental validation tests and the results showed satisfactory. The practical possibility of the derived optimal machining conditions is also analyzed and presented using scanning electron microscope examinations. According to the growing industrial need of making high performance, low cost components, this investigation provide a simple and sequential approach to enhance the WEDM performance while machining MMCs.

Effect of Wire Material on Productivity and Surface Integrity of WEDM-Processed Inconel 706 for Aircraft Application

Inconel 706 is a recently developed superalloy for aircraft application, particularly in turbine disk which is among the most critical components in the gas turbine engines. Recently, wire electrical discharge machining (WEDM) attained success in machining of gas turbine components which require complex shape profiles with high precision. To achieve the feasibility in machining of these components, the research work has been conducted on Inconel 706 superalloy using WEDM process. And, the effect of different wire materials (i.e., hard brass wire, diffused wire, and zinc-coated wire) on WEDM performance characteristics such as cutting speed, surface topography, surface roughness, recast layer formation, residual stresses, and microstructural and metallurgical alterations have been investigated. Even though, zinc-coated wire exhibits improved productivity, hard brass wire was found to be beneficial in terms of improved surface quality of the machined parts. Additionally, lower tensile residual stresses were obtained with hard brass wire. However, diffused wire has a moderate effect on productivity and surface quality. Under high discharge energy, higher elemental changes were observed and also the white layer was detected.

Optimization of wire electrical discharge machining parameters for cutting electrically conductive boron carbide

In this work, Pure boron carbide (B4C) was consolidated using spark plasma sintering (SPS) at 2050°C with a dwell of 10min under 50MPa uniaxial pressure in Argon atmosphere. The sintered specimen was >99% dense and offered characteristic Vickers hardness and fracture toughness of 31.4GPa and 4.21MPa-m0.5, respectively, at 4.9N indentation load. The specimen showed satisfactory wire electrical discharge machining (WEDM) performance because of its good electrical conductivity. The design of experiment (DOE) was arranged by L32 orthogonal array (OA) between the machining input parameters namely pulse on-time, pulse off-time, pulse peak current, dielectric fluid pressure and servo feed rate and the output responses like machining speed and surface roughness (Ra). Regression models were employed to establish the numerical correlation between the machining parameters and output responses. Experimental observations were utilized to formulate the first-order regression models to predict responses of WEDM. The optimized input parameters were 27 μs pulse on time, 48 μs pulse off time, 180A pulse peak current, 7kg/cm2 water pressure and 2200mm/min servo feed rate for the WEDM performance to produce an optimum machining speed and Ra.

On the Effects of Wire Electrode and Ceramic Volume Fraction in Wire Electrical Discharge Machining of Ceramic Particulate Reinforced Aluminium Matrix Composites

In this paper, effect of type of wire electrode material and volume fraction of reinforcement on wire electrical discharge machining performance of A359/SiCp composite has been reported. In this study, a plain brass (CuZn37) wire and a copper wire coated with CuZn50 were used as wire electrodes. The volume fraction of the SiC particulate reinforcement was varied from 10% to 30%. While volume fraction was found to be the most significant parameter affecting the cutting rate, the pulse on-time and the type of electrode material were the next in the order of significance. It is interesting to note that the interaction between on-time and volume fraction as well as the interaction between type of electrode material and pulse on-time also had significant influence on the cutting rate. Further, it was found that the cutting rate was greater in the case of coated wire as compared to the plain brass wire. The improvement in the cutting rate was found to be in greater than 58% for the coated wire. Furthermore, the kerf width was found to be smaller in the case of coated wire compared to the plain brass wire. Nevertheless, the surface roughness was found to increase significantly with the coated wire.