Literature Review on Wedm

Last some decades studies shows that rapid research has been done on WEDM in terms of improving performance measures, optimizing the process parameters, monitoring and controlling the sparking process, simplifying the wire design and manufacture, improving the sparking efficiency by different researchers. The desired work done is further discussed in the upcoming paragraphs.

Azmir azhari et.al (2017) reported that the attainable of cutting polyurethane foam using wire electrical discharge machining (WEDM) process. The foam consists of nickel copper coated polyester (PET) fabric. Three different thicknesses of foam constitute to different surface and volume resistivity was chosen as work piece. The effects of various parameters on machining length was examined.

The endurance of the process is a high-energy loss which results in periodically wire breakages cause of low electrical conductivity of polyurethane foam. In case of accelerating the pulse-on time, the length of cut became shorter since the wire breakage was triggered by showing an abatement in the discharge frequency. The length of cut proliferate with hike in pulse-off time as a result of sufficient time to remove the debris. At a higher peak current, the length of cut exaggerate owing to an increase in current aredency. Due to lower servo voltage the length of cut also reduces but machining at lower voltages was unstable with frequent wire breakages.

Goyal et al (2017) in this investigation cores the effect of process parameters on material removal rate (MRR) and surface roughness (Ra) in wire electric discharge machining of Inconel 625. Machining was completed by using a normal zinc coated wire and cryogenic treated zinc coated wire. The tests were performed by considering different process parameters like tool electrode, current intensity, pulse off time, pulse on time, wire feed and wire tension. The thickness of dia. of wire and work material is kept stable. Taguchi L18 (21*35) orthogonal array of experimental design is used for experiments. Analysis of variance (ANOVA) is assumed to optimize the material removal rate and surface roughness. Based on analysis it is found that pulse on time, tool electrode and current intensity are the imperative parameters that affect the both MRR and SR parameters. The scanning electron microscopy (SEM) is in use to pinpoint the microstructure of the machined work piece.

Singh et al. (2016) reported that since previous ten years, the wire electric discharge machining (WEDM) process commences as a non-conventional machining process employed in manufacturing sector with intricate shapes and variable profiles. However, Al 6063 alloy has innumerable application area which inculcates aerospace industry, automobile industries, medical implants, electronic industry etc. owing to its unique and excellent characteristics: high strength to weight ratio, high wear resistance, improved stiffness, compatibility of operating at elevated temperature and low thermal expansion coefficient. In this research the experiments has been made to carry out investigation to study the effect of process parameters: pulse-on time, pulse-off time, servo voltage, peak current on measure of process performance, i.e. material removal rate (MRR) during WEDM of Al6063 work piece. It is seen from present study that input process parameters have indispensable influence on process performance characteristics. The key features of experimental procedure are also notice worthy.

Mu-tian yan et al. (2016) worked on the mechatronic system approach for the improvement of part straightness accuracy in rough cutting of wire electrical discharge machining (wire EDM). The mechatronic system design integrated an active wire feed apparatus and a microcontroller based wire tension control system into a novel wire transport system for providing a smooth wire transport and a consistent wire tension value. The active wire feed apparatus was came into existence to reduce the inertial effect of the wire spool on the wire transport system. Then, PID controller was used to implement real-time wire tension control of the wire transport system. Compared to a typical wire transport system, steady-state error of wire tension control can be decreased by half using the newly developed system. The ratio of normal sparks to total sparks defined as normal spark ratio can be used to keep a check on spark gap condition along with an indication of evaluating machining speed and part straightness accuracy. Experimental outcomes depicts that part straightness accuracy can be appropriately improved from 13 to 4 µm by the newly developed wire transport system along with optimum machining settings.

G Krishna Mohan Rao et. al. (2014) stated at optimizing the metal removal rate of die sinking electric discharge machining (EDM) by taking into account the simultaneous effect of various input parameters. The experiments are being taken on Ti6Al4V, HE15, 15CDV6 and M-250. Experiments were done by changing the peak current and servo voltage and the values of metal removal rate (MRR) were measured. Multiperceptron neural network models were developed using Neuro solutions package. Genetic algorithm concept is used to optimize the weighting factors of the network. It is anticipated that the developed model is within the limits of the agreeable error when experimental and network model results are compared for all performance measures considered. It is further observed that the maximum error are taken when the network is optimized by genetic algorithm has been reduced considerably. Sensitivity analysis is also conducted to find the relative influence of factors on the performance measures. It is observed that type of material is having more influence on the performance measures.

G.Rajyalakshmi et. al. (2013) applied an effective approach, Taguchi grey relational analysis, experimental results of wire cut electrical discharge machining (WEDM) on Inconel 825 with consideration of multiple response measures. The approach combines the orthogonal array design of experiment with grey relational analysis. The main objective of this study is to obtain improved material removal rate (MRR), surface roughness (SR), and spark gap (SG). Grey relational theory is espoused to analyse the process parameters that optimize the response parameters. The experiment has been done by using Taguchi’s orthogonal array L36 (21×37). Each experiment was conducted under different conditions of input parameters. The response table and the grey relational grade for each level of the machining parameters have been designed. From 36 experiments, the best combination of parameters was examined. The experimental results shows that the proposed method in this study improves the machining performance of WEDM process.

Samar singh et.al (2012) stated that Electric Discharge Drill Machine (EDDM) is a spark erosion process used for the production of micro holes in conductive materials. This process is extremely used in aerospace, dental, medical and automobile industries. As for the performance evaluation of the Electric discharge drilling machine it is very important to study the process parameters of machine tool. In this paper a brass rod of 2 mm diameter was selected as a tool electrode. The experiments generate output responses such as material removal rate. The best parameters such as pulse on-time, Pulse off-time and water pressure were studied for best machining characteristics. This research shows the use of Taguchi approach for better material removal rate in drilling of Al-7075. A design of experiments, based on L27 Taguchi design method, was selected for drilling of material. From the analysis of variance (ANOVA) seen the percentage contribution of the control factor in the machining of Al-7075 in EDDM. The optimal combination levels and the significant drilling parameters on MRR were obtained. The optimization results displayed that the combination of maximum pulse on-time (Ton) and minimum pulse off- time (Toff) gives maximum material removal rate.

U.Natarajan et al. (2011) focuses RSM for the multiple response optimization in micro-end milling operation to gain maximum metal removal rate (MRR) and minimum surface roughness. Aluminium block of 60×40×16 mm is used as the work piece material and carbide end mill cutter of diameter 1 mm as the cutting tool. Jangra Kamal et al. (2010) presented the optimization of performance characteristics in WEDM using Taguchi Grey relational analysis. Process parameters were investigated using mixed L18 orthogonal array. GRA was applied to determine optimal process parameters for optimization of multiple performance characteristics which were introspected during rough cutting operation in D-3 tool steel.

H.Singh et al. (2009) found that the material removal rate (MRR) directly escalates with increase in pulse on time and peak current while decreases with increase in pulse off time and servo voltage. They used ELECTRONICA SPRINTCUT WEDM as a machine tool and hot die steel (H-11) as work-piece. Mohammadi et at. (2008) the setting of machining parameters reckon strongly on the experience of operators and machining parameter tables given by machine tool builders. It is difficult to utilize the optimal functions of a machine owing to there being too many adjustable machining parameters. Kanlayasiri et al. (2007) investigated influences of wire-EDM machining variables on surface roughness of newly developed DC 53 die steel of width, length, and thickness 27, 65 and 13 mm, respectively. The machining variables included pulse-on time, pulse-off time, pulse-peak current, and wire tension. The variables affecting the surface roughness were identified using ANOVA technique. Results showed that pulse-on time and pulse-peak current were significant variables to the surface roughness of wire-EDMed DC53 die steel. The maximum prediction error of the model was less than 7% and the average percentage error of prediction was less than 3%.

Huang et al. (2006) displayed the surface alloying behaviour of tempered martensitic stainless steel multi-cut with WEDM. Before machined with WEDM, the steel specimens were quenched at 10500C and then tempered at 2000C, 4000C, and 6000C, respectively. The microstructure and surface morphology of the multi-cut surfaces were examined with scanning and transmission electron microscopes integrated with an energy-dispersive X-ray spectrometer for chemical composition analysis. Scott F.Miller et al. (2005) studied the WEDM of cross-section with minimum thickness and compliant mechanisms. Effects of EDM process parameters, particularly the spark cycle time and spark on-time on thin cross-section cutting of Nd–Fe–B magnetic material, carbon bipolar plate, and titanium are investigated. An envelope of feasible wire EDM process parameters is generated for the commercially pure titanium. The application of such envelope to select suitable EDM process parameters for micro feature generation is demonstrated. Scanning electron microscopy (SEM) analysis of EDM surface, subsurface, and debris are presented.

Han et al. (2004) Describes the improvement of machining characteristics of micro electrical discharge machining (micro-EDM) using a newly developed transistor type isopulse generator and servo feed control. The RC generator is mainly applied in conventional micro-EDM even though the transistor type isopulse generator is generally more effective for obtaining higher removal rate.

Wang et al. (2004) Develop a computational method for numerical control (NC) of travelling WEDM operation from geometric representation of a desired cut profile in terms of its contours. Normalized arc length parameterization of the contour curves is used to represent the cut profile and a subdivision algorithm is developed together with kinematics analysis to generate the required motions of the machine tool axes. In generating the tool motions for cutting sections with high curvatures such as corners with small radii, a geometric path lifting method is presented that increases the machining gap and prevents gauging or wire breakage.

Obara et al. (2004) Described corrosion of a work-piece of cemented carbide submerged in a dielectric of water for a lengthy time during WEDM. When the cemented carbide is submerged in water for a long time, the surface of the cemented carbide becomes brittle, because the cobalt which is the binder of cemented carbide is dissolved in the water. This occurs even if an AC power generator is used during the wire EDM. A.B. Puri et al. (2003) Experimented on the wire lag phenomenon in WEDM and the trend of variation of the geometrical inaccuracy caused due to wire lag with various machine control parameters has been established. In an extremely complicated machining process like Wire-cut EDM, which is governed by as many as ten control factors, it is very difficult to select the best parametric combination for a particular situation arising out of customer requirements. In their research study, all the machine control parameters are considered simultaneously for the machining operation which comprised a rough cut followed by a trim cut. The objective of their study has been to carry out an experimental investigation based on the Taguchi method involving thirteen control factors with three levels for an orthogonal array L27 (313). The main influencing factors are determined for given machining criteria, such as: average cutting speed, surface finish characteristic and geometrical inaccuracy caused due to wire lag. Also, the optimum parametric settings for different machining situations have been found out.

From the earlier literature instance, it can be concluded that some of the researchers uses wire electric discharge machining on the various work-piece materials. Present research have been conducted the machining of the M6 Steel using varying the different control factors of WEDM to improve the material removal rate, to surge the surface roughness. Several researches have been conducted these experiments to improvise the other various machining parameters which are used in machining.

• The effect of machining parameters on M6 steel has not been fully explored or it can be say that very little research is done on optimization on this material.
• Literature review depicts that the numerous researchers have carried out most of the work on WEDM developments, control and monitoring but very limited work has been presented on optimization of process variables.
• Various parameters of WEDM like Pulse ON, Pulse OFF, Peak Current, Spark voltage are used for the machining purpose.
• Analysis of effects of various parameters on MRR and Surface Roughness has not been introspected yet.