PARAMETERS OPTIMIZATION OF WIRE EDM FOR CUTTING SPEED USING TAGUCHI

Transcription

1 PARAMETERS OPTIMIZATION OF WIRE EDM FOR CUTTING SPEED USING TAGUCHI TECHNIQUE Jasvinder Pal, Nishant, Ajay Lohan Student, Assistant Professor,, Department of Mechanical Engineering, OITM, Hisar Abstract--In this paper, the wire-edm of Nickel alloy (Nimonic-80) is studded. Nimonic- 80 is used in aerospace industry owing to its high strength at high temperature, fatigue and corrosion resistance. Present work focuses on the machinability of Nimonic-80 with electrical discharge machining (WEDM) process. Influence of WEDM parameters namely Pulse on time, Pulse off time, Peak current, Wire feed and Servo voltage has been investigated on cutting speed of Nimonic-80 Keywords: Cutting speed, Machinability, Nimonic-80, WEDM. I. INTRODUCTION Nickel based alloy are widely used in high temperature and high corrosion environment application such as aerospace industry, various thermal processing, Marine engineering etc. Machining characteristics of Nickel based alloy can affect the working life of its component. Several attempts are made to evaluate the machining characteristics of Nickel based alloy with conventional machining method. Kartabarria et al., (0) reported on residuals stress profiles on Inconel 78 developed by dry face turning. Wire electrical discharge machining (WEDM) is the best non-conventional machining process to overcome the difficulties in machining of Nickel alloy. WEDM is a special form of electrical discharge machining. Which has the capability to produce intricate shapes and profiles in hard matel alloy with high degree of accuracy, without making any mechanical contact. In WEDM, Surface material is eroded by melting or evaporation due to large amount of heat generated between the work material and downward moving wire electrode. An analysis of effect of various machining characteristics is required for successful utilization of process with high productivity. This study analyzes effects of various process parameters (Pulse-on time, Pulse-off time, Peak current, Wire feed, servo voltage) on machining characteristics of CNC WEDM II. METHODOLOGY A scientific approach to plan the experiments is a necessity for efficient conduct of experiments. By the statistical design of experiments the process of planning the experiment is carried out, so that appropriate data will be collected and analyzed by statistical methods resulting in valid and objective conclusions. When the problem involves data that are subjected to experimental error, statistical methodology is the only objective approach to analysis. Thus, there are two aspects of an experimental problem: the design of the experiments and the statistical analysis of the data. These two points are closely related since the method of analysis depends directly on the design of experiments employed. The advantages of design of experiments are as follows: Numbers of trials is significantly reduced. Important decision variables which control and improve the performance of the product or the process can be identified. ISSN Page 7

2 Optimal setting of the parameters can be found out. Qualitative estimation of parameters can be made. Experimental error can be estimated. Inference regarding the effect of parameters on the characteristics of the process can be made. Table.: Process parameters and their levels In the present work, the Taguchi s method, have been used to plan the experiments and subsequent analysis of the data collected. For this experimental work the five process parameters, one at two and four at three levels have been taken to reflect the true behavior of output parameters of study. The process parameters and their level is shown in Table. Symbol Process Parameters Level Level Level A Servo Voltage (SV) B Pulse off Time(μs) Toff C Pulse-on time (μs) Ton 06 8 D Peak Current (Amp) Ip E Wire Tension Value of the process parameters levels have been taken on the base of results of pilot experiments, literature review and expert knowledge & experience. Results of trial experiments were indicated that the cutting rate increases with the increase in the pulse on time in a practically straight line fashion. The cutting rate decreases with the increase in the pulse off time. The cutting rate remains practically constant with the increase in wire feed whereas the surface roughness though remains practically constant. III. Results and analysis The experiments were conducted to investigate the effect of process parameters on the machining characteristic cutting rate. The experimental results are discussed subsequently in the following sections. The experiments were performed. And Cutting Speed (CS ) was measured. MRR was measured in mm/min. which was observed from machine tool monitor screen. Table.: Experimental Results Exp. No. SV Toff Ton Ip WT CS (mm/min) ISSN Page 8

3 Average.77 Table. and Table. is Cutting speed and S/N Ratio for Cutting Speed. The Cutting speed and S/N ratio for cutting and is then plot with the help of Minitab software to find the optimal solution Table.: S/N Ratio for cutting speed Exp. No. SV Toff Ton Ip WT S/N ratio Cutting Speed ISSN Page 9

4 Effect On Cutting Speed In this section we discuss the effect of above mention process parameters on cutting rate. In order to see the effect of process parameters on cutting rate, experiments were performed. The average values of cutting rate for each parameter at levels, and for raw data and S/N data are tabulated in table. and.4 respectively. And the same average values for raw data and S/N data are plotted in figure and respectively. Table.: Response table for Cutting Speed (Raw Data) Level SV Toff Ton Ip WT For example, the average effect on MRR (Raw data) for parameters A at level can be calculated as follows: A = ( ) / 9 =.06 Table.4: Response table for Cutting speed (S/N Data) Level SV Toff Ton Ip WT For example, the average effect on CS (S/N data) for parameters A at level can be calculated as follows: ISSN Page 0

5 A = ( )/9 = Main Effects Plot for Mean CS Data Means. SV Toff Ton.0.8 Mean of Means Ip WT Figure : Effects of response of Process Parameters on Cutting speed Main Effects Plot for SN ratios [CS] Data Means 7 SV Toff Ton 6 5 Mean of SN ratios Ip WT 5 4 Signal-to-noise: Larger is better Figure : Effects of response of Process Parameters on Cutting Speed (S/N Data) ISSN Page

6 From figure and, it is clear that the cutting speed increases with the increase of pulse on time, and wire Tension, and decreases with increase in pulse off time and servo voltage. This is because the discharge energy increases with the pulse on time which results in faster cutting rate. As the pulse off time decreases, the number of discharges within a given period becomes more which leads to a higher cutting rate. With increase in servo voltage the average discharge gap gets widened resulting into a lower cutting rate. The effect of wire tension on cutting Speed is not very significant. Conclusion Selection of optimum process parameters have been made from the response table. Here response table is used to calculate the effect of each level of process parameter on performance measure. The response tables. and.4 show the average of each response characteristic (Raw data, S/N data) for each level of each factor. As cutting rate is the higher the better type quality characteristic, it can be seen from Figure that the first level of servo voltage (A), first level of pulse off time (B), third level of pulse on time (C), first level of peak current (D), and first level of wire tension (E) provide maximum value of cutting rate. The S/N data analysis (Figure ) also suggests the same levels of the variables (A, B, C, D and E) as the best levels for maximum CS in WEDM process. Reference [I] C. L. Lin, J. L. Lin and T. C. Ko (000), Optimization of the EDM process based on the orthogonal array with fuzzy logic and grey relational analysis method, International Journal of Machine Tools and [II] [III] Manufacture, Volumes 9, pp A.B. Puri, B.Bhattacharyya (00), An analysis and optimization of the geometric inaccuracy due to wire lag phenomenon in WEDM, International Journal of machine Tools and Manufactur, Volume 4, pp B.R. Sridhar, G. Devananda, K. Ramachandra, Ramaraja Bhat (00), Effect of machining parameters and heat treatment on the residual stress distribution in titanium alloy IMI-84, Journal of Materials Processing Technology 9, PP [IV] Biing Hwa Yan, Hsien Chung Tsai and Fuang Yuan Huang (005), The effect in EDM of a dielectric of a urea solution in water on modifying the surface of titanium, International Journal of Machine Tools and Manufacture, Volume 45, pp [V] C.J. Luis and I. Puertas (007), Methodology for developing technological tables used in EDM processes of conductive ceramics, Journal of Materials Processing Technology, Volume 89, pp [VI] Aman Aggarwl, hari Singh, pradeep kumar, manmohan Singh (008). Optimization of multiple quality characteristics for CNC turning under cryogenic cutting environment using desirability function. J. Material process. technol. [VII] Aniza Alias, Bulan Abdullah ( 0 ), Influence of machined feed rate in WEDM of Titanium Ti-6 AL-4V with constant current(6a) using brass wire International Symposium on Robotics and Intelligent Sensors 0 (IRIS 0) Norliana Mohd Abbas Procedia Engineering 4 PP ISSN Page