Non-conventional Machining Process Research Articles

Investigating the influence of electrical discharge machining process parameter on fatigue strength during machining of titanium grade-2

High strength, excellent corrosion resistance, and low density are the main properties that make titanium attractive for a variety of applications such as the production of airframes, engine components, steam turbine blades, superconductors, missiles, etc. Machining of titanium alloy by conventional machines causes the problems such as chipping and premature tool failure, deflections of the work-piece, increases the temperature at the tool-work piece interface, etc. Hence under such circumstances, nonconventional Die sink Electrical Discharge Machining (EDM) process can be alternative to overcome such problems. The primary aim of this paper is to investigate the effects of process parameters (factors) on material removal rate (MRR) in the EDM process. The process parameters considered for this investigation are current (C), voltage (V), pulse on time (Ton), and pulse off time (Toff) for EDM machining of titanium (grade-2) alloy with copper as an electrode material. The experiments were designed with the Taguchi method, orthogonal array L9. The maximum MRR obtained was 0.073 mm3/min with the voltage of 40 V, current of 8A, pulse on at 60 µs, and pulse off at 9 µs respectively. While the secondary aim of this research is to investigate the effect of process parameters on fatigue strength of titanium (grade-2) alloy. During fatigue test it was observed, fatigue strength decreases with an increase in current and pulse on time.

Multi-response optimization in wire electrical discharge machining (WEDM) of D2steel using utility approach

Wire electrical discharge machining (WEDM) is a popular non-conventional machining process used particularly for making extrusion dies, blanking punches, and tools especially requiring tight dimensional tolerances. Because of the process limitation, the rate of cutting and maintenance of close dimensional tolerance is a challenging task. Given the above facts, the present work has been focused on achieving the maximum possible cutting rate (VC) maintaining good dimensional accuracy and corner radius (RC). In the present research work, a multi-response optimization method (i.e. Taguchi based Utility approach) has been used to obtain an optimum set of input parameters such as pulse on time (TON), pulse off time (TOFF), servo voltage (SV), and wire feed rate (WF) resulting into a best overall cutting performance. Analysis of variance (ANOVA) is also used to find out the significant effect of each machining parameter on the cutting performance. The analysis reported in this paper will be helpful for industry personnel to select the best set of process parameters for achieving a good result without the use of any software or statistical analysis.

Comparative study of parametric effects on the performance of simple and powder mixed EDM using aluminium and graphite powder on Inconel X750 alloy

In the present scenario, Electrical Discharge Machining (EDM) is one of the most entrenched non-conventional machining processes which are widely used in different manufacturing sectors worldwide. Generally, the conductive materials, which having geometrically complex shape and extremely difficult to machine by conventional machining processes are machined by EDM. The further improvement of the machining efficiency of this EDM process may be enhanced by using powder suspended dielectric fluid which is called Powder Mixed EDM (PMEDM) process. In this research work, an attempt has been made to analyze the comparative study of parametric effects on the performance characteristics like material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) in terms of average value of roughness parameter (Ra) of simple (without powder) and powder mixed EDM using Aluminium (Al) and Graphite powder on Inconel X750 alloy by experimental investigation. Here, in our study, Peak current (Ip) pulse on time (Ton) and pulse off time (Toff) have been taken as the variable process parameters and concentration of powder (Cp) is taken as 6 g/l in all cases throughout the experimentation. From the experimental results, it has been observed that PMEDM gives lower MRR but better surface finish in comparison with conventional EDM technique (without powder). Also, it has been noticed that graphite powder mixed EDM is more effective for getting better surface finish of Inconel X750 alloy compared to Al mixed PMEDM process.

Multi performance optimisation of wire-cut EDM process parameters of Incoloy 800 alloy using grey relational analysis

Abstract Wire Electric Discharge Machining is one of the non-conventional machining processes, used to machine alloy materials with high mechanical strength and also cuts intricate shapes. This paper presents a study in multi performance optimization of machining parameters of Wire electric discharge machining of Incoloy 800 alloy using Taguchi method and grey relational analysis. Incoloy 800 alloy is a nickel, iron and chromium based alloy. The variation in process parameters affects the response variables such as Surface roughness and Material removal rate. Taguchi L27 Orthogonal array is used to perform the experiments. Experiments are performed by considering machining parameters such as Pulse on time, Pulse off time, Gap Voltage, Peak current. By varying the machining parameters accordingly the optimum values are obtained for performance characteristics. The optimization is performed in order to obtain best Surface Roughness and maximum Material Removal Rate. By Grey relational analysis the optimal combination of machining parameters is obtained. ANOVA reveals the most influential factor for Surface roughness and MRR. The results show that the machining parameter Pulse ON time has the greater impact on the performance characteristics.

Effect of recirculation zone on debris evacuation during EDM deep hole drilling

Deep hole drilling is a technique used for producing holes in materials at high depth to diameter (L/D > 10) ratios. Applications demanding deep holes can be extensively found in aerospace, automotive, marine and oil & gas industries. Conventional drilling techniques such as twist drilling and gun drilling are commonly used for drilling deep holes in the aforementioned applications. However, these methods can cause problems of rapid tool degradation, chip clogging, premature tool failure and undesirable sub-surface alterations to the hole surface. Moreover, these problems get aggravated when the material is difficult-to-cut (Ni/Fe/Co based superalloys) in nature. Therefore, non-conventional machining process finds scope in order to overcome the problems associated with conventional drilling. Electrical discharge drilling (EDD) can be used for fabricating dimensionally accurate holes irrespective of hardness of the material. Nevertheless, the inefficiency in flushing of debris particles at higher depths and its subsequent accumulation is a critical challenge during EDM deep hole drilling. The reason behind flushing inefficiency based on fluid physics has not been completely explored by researchers yet. In this paper, the flow behaviour of micro debris particles in the flushing channel during EDD has been analysed using CFD simulation by employing discrete phase modelling (DPM). The developed model set up is also validated with a benchmark fluid mechanics problem. The steady state CFD analysis results show the formation of multiple recirculation zones in the flushing channel. This can be attributed to the adverse pressure gradient experienced when the dielectric fluid passes from the machining gap to annular gap. Moreover, the presence of recirculation zones reduces the flow momentum and thereby debris particle velocity. This leads to accumulation of micro debris particles in the recirculation zones over time. The results also show that the trajectory of the particles is dependent on the size of the particles generated during material removal. The outcomes of numerical analysis in the present paper can serve as a foundation for the future studies in improving the performance of EDM deep hole drilling.

ON THE MACHINING OF ALUMINUM ALLOY AL6063 WITH EDM

Electrical Discharge Machining (EDM) is a non-conventional machining process, which allows the machining of any electrical conductive material, regardless its mechanical properties, with high dimensional accuracy, and in complex shapes and geometries. EDM widely utilized by modern industry, taking advantage of its unique inherent capabilities. Aluminum alloys find extensive use in numerous applications, and their machining consist an interesting topic, with tangible industrial interest. The current study presents an experimental investigation of machining Al6063 alloy with EDM. A full scale experiment was conducted, with control parameters the pulse-on current and time. The productivity of the process calculated based on the Material Removal Rate (MRR), while the Surface Roughness of the machined surfaces was estimated in terms of Ra and Rt. For these performance indexes Analysis Of Variance was performed and semi-empirical relations that correlate machining parameters with obtained results were proposed. Finally, the cross sections of the specimens were observed in optical microscopy, in order the formation of the White Layer to be studied.

Optimization of process parameters of electrical discharge machining of fabricated AA6082 – ALN

The non-conventional machining methods are used for machining very hard materials and for making difficult shapes. Electrical discharge machining (EDM) process is one of the most commonly used nonconventional machining processes for machining hard, brittle materials like composites. It is commonly used in die making industries for developing complex profiles in dies related to sheet metal work etc., It is commonly used for machining metal matrix composites which are very hard materials. Aluminium based metal matrix composites are widely used in aeronautical and defence parts because of their advanced properties like high strength to weight ratio, etc. At first the material was fabricated using stir casting set up which was the part of research work. The work piece material selected in this study was Aluminium alloy 6082 and 10% Aluminium nitrite based metal matrix composite which was fabricated by stir casting process with the help of newly developed stir casting set up. After fabrication, the characterization of samples was done using SEM and mechanical. The EDM process was selected for machining composite samples with input parameters like gap current (A), pulse on time (μs) and duty factor. In this machining process the output response was material removal rate. The optimization of process parameters was done using Taguchi method with the help of ANOVA test and S/N ratio. Analysis of variance was performed to find the significance of machining parameters in this experimental work.

Dielectric Fluid Parameter Optimization in Machining of Composite Material using WEDM Process

Wire Electric Discharge Machining (WEDM) has become most popular among the non-conventional machining processes because of precise machining and accuracy of parts. The process is preferable for accurate machining of complex geometries in hard materials such as Aluminium Silicon Carbide metal matrix composite. In this work, an attempt is made to analyze and optimize the dielectric fluid parameters in machining of Al/SiCp 10% work material. The input variables such as volume flow rate, flow velocity and chemical composition of dielectric medium used in the WEDM are chosen for this. Taguchi’s L9 orthogonal array is used to conduct experiments in WEDM machine and ANOVA results have confirmed the influence of chosen parameters on the output responses. Computer simulation model of the WEDM tank with dielectric fluid, work piece and nozzle is presented using Fluent software. The Fluent model is analyzed based on the maximum removal of debris in the work material. Optimization is carried out to maximize the Material Removal Rate (MRR) and minimize surface roughness. The results obtained from Taguchi’s optimization and Fluent analysis have been validated by carrying out tests on WEDM. The study shows that volume flow rate and flow pressure can adequately influence MRR and surface roughness.

Analysis of multi-spark in wire electrical discharge machining

Electrical discharge machining plays a vital role in precision manufacturing processes. It is a non-conventional machining process in which electrical energy is converted into thermal energy by means of spark in a Di-electric fluid medium. Due to generation of temperature above melting point the material removal takes place. This paper presents the analysis performed on Aluminium 6061 – T6 Alloy with single-spark and multi-spark machining situations to predict temperature distribution and material removal rate. Gaussian heat flux distribution is used to simulate heat flux and four pulses are considered in multi-spark case in thermo-physical model. The results of single-spark and multi-spark simulated machining process were compared and it is observed that material removal rate and temperature distribution are higher in multi-spark simulated machining as compared to single spark.

Experimental investigation on micro-electro discharge machining process using tungsten carbide and titanium nitride-coated micro-tool electrode for machining of Ti-6Al-4V

ABSTRACT Titanium alloy Ti-6Al-4 V is used in numerous applications because of its low weight associated with high strength, excellent resistance to fatigue and creep, good resistivity in corrosive environments, and biocompatibility. The Micro-Electro Discharge Machining (MEDM) is one of the finest non-conventional machining processes used for machining Ti-6Al-4 V. In this research article an attempt has been made to study effect of thin film coating of titanium nitride (TiN) on tungsten carbide (WC) micro-electrode on tool wear rate (TWR), over cut (OC) and depth of machining (Z coordinator) during micro-drilling of Ti-6Al-4 V. A detailed experimental investigation has been carried out with the help of Taguchi’s L9 orthogonal array for understanding the mechanism of the process. The process parameters such as voltage, spindle rotation and capacitance are considered to perceive their effect on TWR, OC and Z coordinator. Uncoated WC and TiN-coated WC micro-tool electrodes has been used during machining Ti-6Al-4 V in order to compare listed responses. The experimental results of TiN-coated micro-electrode showed that TWR decreased by 16.32 %, depth of machining increased by 20.83% and OC reduced by 12% as compared to uncoated WC micro-tool electrode.

Recent advancement in electric discharge machining of metal matrix composite materials

Spark Erosion Machining which is also known as Electric Discharge Machining (EDM) is one of the most commonly used non-conventional machining process for the machining of electrically conductive materials by utilizing precise controlled spark which take place between a tool and work piece in the presence of dielectric liquid. Presently in now days EDM procedure is usually utilized for machining of advanced material such as ceramic, composite, metal matrix composite (MMC), ceramic matrix composite (CMC) etc. which have immense applications in automobile, aerospace, shipyard and railway application. Presently among all MMC material aluminium MMC material are mostly used because of their outstanding properties such as low density, remarkable wear and corrosive resistance, tensile strength and low coefficient of thermal expansion. It is very difficult to machine MMC material with help of conventional machine because of high tool wear rate and high tooling cost. Nonconventional machining provides a provision to machine such a material efficiently. This paper represents a review of EDM on MMC material, effect of electrical and non electrical parameter on the machining characteristics, optimization of EDM parameter and determination of more optimistic methodology. This paper also reveals some future research trend that can be performed in future in the same region.

Surface texture and integrity of electrical discharged machined titanium alloy

Electrical discharge machining (EDM) is a non-conventional machining process, extensively applicable in the modern industry. Owing the non-contact nature of the process, any electrical conductive material can be machined in high quality, regardless its mechanical properties. Titanium alloys are commonly machined by EDM, as difficulties related with their low thermal conductivity and the high chemical reactivity can be overcome. As titanium alloys are utilized in quality demanding applications and industries, high machined surface quality is required, as well surface integrity. The current study presents an experimental investigation of how ED machining parameters affect the MRR, the TWR, and the SQ on machining Titanium Grade 2 by EDM. For pulse current 9/13/17/25A, and pulse on time 25/50/100/200 μs, a full-scale experiment has been carried out, using graphite electrode. The surface texture (ST) has been estimated in terms of arithmetic mean height (Sa), maximum height of scale-limited surface (Sz), and skewness of the scale-limited surface (Ssk), while also measurements of the surface waviness were conducted as well. For all the aforementioned parameters an analysis of variance (ANOVA) has been performed. Finally, the surface topography and integrity were evaluated through optical and SEM microscopy observation, through which the surface cracks and micro-cracks due to high pressure and temperature gradients can be distinguished and characterized.

Effects of stepped cylindrical electrode in electrical discharge machining of blind holes

Electrical discharge machining (EDM) is a non-conventional machining process which has been widely used to machine difficult-to-cut materials. However, the efficiency of EDM hole making processes is low, and the quality of drilled holes is a concern especially when machining deep blind holes due to the poor removal of debris in the discharging gap. In this study, a new strategy based on shape modification of the electrode was developed to address this issue by indirectly changing the flow of dielectric. The electrodes of five different shapes with identical machining area were applied to improve the debris removal during the machining process. The effects of various electrode profiles on the machining performance were investigated. Machine time, material removal rate (MRR) and electrode wear rate (EWR) were used to evaluate the machining performance. The computational fluid dynamic (CFD) software Fluent was used to simulate the flow of dielectric caused by different electrode profiles. The results show that, compared with the straight electrode, the maximum effective cutting depth of curved electrodes and long-curved electrodes increased 13.793% and 132.184%, respectively, and the MRR of stepped electrodes was significantly higher after the machining depth reached 2 mm and 4 mm for electrodes with the working length of 2 mm and 4 mm, respectively. The surface roughness was identical for holes machined by all types of electrode. However, obvious carbon adhesion can be observed at lower cutting depth for straight electrode, followed by curved and long-curved electrodes.

A REVIEW OF RECENT METHODS FOR TOOL WEAR REDUCTION IN ELECTRICAL DISCHARGE MACHINING

Electrical discharge machining (EDM) is one of the most explored nonconventional machining processes due to its ability to machine intricate shapes on conductive materials. However, tool wear is one of the major challenges in the EDM process as it directly affects the accuracy of machining, surface roughness, reproduction of geometrical characteristics on the workpiece and cost of the process. Lots of work have been done to minimize the tool wear by improving the discharge conditions by controlling the EDM process parameters, varying the dielectric characteristics, powder-mixed dielectric methods and ultrasonic-assisted methods. However, minimizing the tool wear by the above approaches also constrains the material removal rate from the workpiece and accuracy of the process. This review highlights the efforts done by the researchers to improve tool wear by recently developed techniques or modifications. Researches available in the field of using treated tool electrode, cooled tool electrode, coated tool electrode, noble tool materials and other techniques are highlighted.

On near-dry wire ECDM of Al6063/SiC/10p MMC

ABSTRACT Metal matrix composites (MMC’s) with their exceptional properties are gaining importance in many industries (i.e., automobile, structural, aerospace, etc.). The secondary processing of MMC’s, like machining, is challenging and sometimes infeasible by conventional machining processes. The present study reports development and investigation on a new non-conventional hybrid machining process named near-dry wire electrochemical discharge machining (ND-WECDM). The investigation involved understanding the material removal mechanism of developed ND-WECDM for machining of Al6063/SiC/10p MMC. A detailed experimental investigation was planned and conducted using Taguchi’s L18 mixed-level design. The influences of input parameters (i.e., pulse on-time, applied voltage, mist flow rate, wire feed rate, and pulse off-time) were analyzed on the slit width (SW) and slit depth (SD) as the performance characteristics. The significant parameters affecting the ND-WECDM process were identified by applying the ANOVA. The SW and SD were most affected by the applied voltage and pulse on-time, respectively. In the ND-WECDM process, material removal is due to electric discharge (ED), electrochemical dissolution (ECD), and thermal spalling (TS). ND-WECDM process is found competent to develop micro features on Al6063/SiC/10p MMC.

A Visual Contrast–Based Fruit Fly Algorithm for Optimizing Conventional and Nonconventional Machining Processes

Swarm intelligence has been extensively adopted to develop and deploy optimization algorithms to almost all branches of science and engineering. In this paper, a visual contrast–based fruit fly algorithm (c-mFOA) is presented to push further the improvement of intelligent optimization when it comes to general engineering problem solving with emphasis to conventional and nonconventional manufacturing processes implemented to modern industry. In this fruit fly algorithmic variant, the natural mechanisms of surging, visual contrast, and casting are incorporated to enhance the algorithm’s exploration and exploitation. The proposed algorithm has been tested to optimize a set of known, widely used benchmark functions and is further implemented to optimize the process parameters of machining processes namely turning; focused ion beam micro milling; laser cutting; wire electrodischarge machining; and microwire electrodischarge machining. The results obtained by examining the multiple solutions, their nonparametric statistical outputs, and hypervolumes of their related Pareto fronts, suggest clear superiority of the c-mFOA against its competing multiobjective optimization algorithms (MOEAs).

Abrasive waterjet machining of fiber-reinforced composites: a state-of-the-art review

Fiber-reinforced composites have established as a high-performance composite of modern advanced structures in various sectors such as automotive, aerospace, and marine industries. Non-conventional machining processes are preferred for the ease of manufacturing operations, which incorporates the machining of high strength and anisotropic material. Non-conventional manufacturing processes produce complicated shaped profiles and better surface characteristics. Abrasive water jet (AWJ) machining is an emerging technology that offers an excellent alternative among the various advanced machining processes due to its process capabilities and excellent machining quality. AWJ machining has fascinated immense attention in the fields of fiber-reinforced composite materials to produce intricate industrial components and attracted the researchers and production industries. It has become well-known in all key areas of researches. Over the past 30 years, lots of research work has been carried out to describe the machining performances among the studied process parameters. This paper reviews the research progresses and integrated functions of AWJ machining in terms of mechanism and machining performances, which includes aspects such as mathematical modeling and optimization. AWJ machining procedure and performance capability are reviewed and depicted in detail. Also, a comprehensive conclusion of this review, along with future perspective, is explored subsequently. The current review work will help future researchers for the proper selection of different FRP material composite compositions and AWJ machining parameters to achieve better performances. The collection of this review literature will also support the production operations in the future.

Experimental investigations on WEDM process for machining High Manganese steel

ABSTRACT High Manganese steel ASTM A128 is a very hard metal and production of components using a conventional machining process is very difficult and also the quality of the products are not favorable for the efficient function. Wire Electrical Discharge Machining (WEDM) is an emanating approach in the non-conventional machining process to produce intricate products with more accurate and precise. The WEDM process is affected by the number of process factors. Hence, appropriate process factor combination is necessary for achieving economical and quality machining. In this investigation, the process factors which include Peak-current Wire-feed, Open-circuit voltage, and Time-off have been considered and Central Composite Design (CCD) was implemented to layout the exploration. Response Surface Methodology (RSM) was utilized to learn the correlation between process factors and to develop mathematical models for responses which include Surface roughness Ra, Rq and Rz, Hardness, and Material Removal Rate (MRR). Analysis of Variance (ANOVA) scrutiny unveiled that the factor Peak-current is the foremost influencing process factor for MRR and Surface roughness parameters. Open-circuit voltage and Wire-feed are the primary influencing process factors for Hardness. The results of verification test showed that the developed mathematical models were good with sufficient accuracy.

Experimental investigation on electro discharge machining of Ti6Al4V alloy

ABSTRACT Ti6Al4V is an alpha-beta titanium alloy, extensively used in aerospace engineering, gas turbines, also in other industries. Features like high strength to weight ratio, high corrosive resistance have made it very much useful in industries. EDM is one of the most popular and powerful non-conventional machining process, capable of machining this type of difficult-to-machine conductive material. The main drawback of EDM is adhesion of debris in between electrodes which disturbs stability of the spark and affects machining rate and quality of machining. In the present research, this problem has been addressed by modification of tool shape, making the face of the tool tapered. Here, full factorial set of experiments has been carried out to investigate the effect of various process parameters, like gap current, pulse-on-time, duty cycle and effect of tapered tool, on material removal rate and tool wear rate. It has been observed that using tapered tool machining rate has been improved, but tool wear rate has been increased using tapered tool. In this paper, SEM photograph of machined hole has been inspected and it is observed that the thickness of the recast layer is smaller and uniform using tapered tool.

Comparison between EDM and grinding machining on fatigue behaviour of AISI D2 tool steel

Non-conventional machining processes, such as the Electrical Discharging Machining (EDM) offers the possibility to machine very hard materials with great potential to generate complex geometries. However, the EDM process involves significant microstructural changes in the as machined surfaces, which are known to have a significant impact on fatigue behaviour of mechanical parts. This study aims at investigating the fatigue behaviour of the AISI D2 tool steel subjected to EDM machining. Both smooth and notched specimens are tested aiming at assessing the fatigue notch sensitivity of this material and results compared with conventional grinding techniques in terms of fatigue resistance and residuals stresses. The AISI D2 steel shows a microstructure composed of large dendritic primary carbides detrimental to the fatigue resistance. Also, the EDM process is responsible for the generation of detrimental tensile residual stresses that justifies the lower fatigue resistance when compared with the ground material that exhibits beneficial compressive residual stresses. The fatigue test data of the notched specimens machined by EDM process show a high fatigue notch sensitivity of the AISI D2 tool steel. The heterogeneous structure of the material, showing large undissolved carbides, leads to a notch fatigue reduction factor that is higher to the apparent theoretical elastic stress concentration factor.