IDL - International Digital Library Of Technology & Research Volume 1, Issue 5, May 2017
Available at: www.dbpublications.org
International e-Journal For Technology And Research-2017
Parametric Optimization of Tool Wear Rate (Twr) on Die Sinking EDM by Using Taguchi and Anova M. Ramadas 1 , Dr.J.S.Soni2 , Dr.T. Vijaya Babu3 1
Associate Professor , Nishitha College of Engineering and Technology ,Lemoor (V), Hyderabad ,India 2 Professor Bharat Institute of Engineering and Technology , Ibrahimpatnam , Hyderabad ,India 3 Professor , Department of Mechanical Engineering, Vardhaman College of Engineering , Shamshabad , Hyderabad 1
das.7442012@gmail.com, 3 tirividhivijaybabu@gmail.com
Abstract: Electric Discharge Machining (EDM) is a unconventional machining process where intricate and complex shapes can be machined. Only electrically conductive materials can be machined by this process. These materials are being widely used in die and mould making industries, aerospace, aeronautics and nuclear industries. In this work DIN 1.2714 steel is the material used for the machining purpose and Copper is used as an electrode. In this process Taguchi approach is used to create L27 orthogonal matrix. Experiments were conducted with the L27 orthogonal array based on the Taguchi method. Moreover, the signal-to-noise ratios associated with the observed values in the experiments were determined. The purpose of ANOVA to see the individual effect of control factors on MRR and TWR. In the present work, Optimization of TWR on EDM conducted by using Taguchi and ANOVA. Keywords: Die sinking EDM machine, tool wear rate, Taguchi’s method, ANOVA 1. INTRODUCTION Electrical-discharge machining (EDM) is an unconventional, non-contact machining process where metal removal is based on thermo-electric principles. In this process, the material removal mechanism uses IDL - International Digital Library
the electrical energy and turns it into thermal energy through a series of discrete electrical discharges occurring between the electrode and work piece immersed in an insulating dielectric fluid . Electrical Discharge Machining (EDM) is a process of material removal using an accurately controlled electrical discharge (spark) through a small gap (approximately 10 to 50 microns) filled with dielectric fluid between an electrode and a work piece. The hardness of the work piece has no effect on the process. Electrically conductive material is removed by controlled erosion through a series of electric sparks of short duration and high current density between the electrode and the work piece, both the work piece and tool is submerged in a dielectric bath, containing kerosene or distilled water. During this process thousands of sparks per second are generated, and each spark produces a tiny crater in the material along the cutting path by melting and vaporization. The objective of the present work is to find a suitable process parameters to minimize the tool wear rate using DIN 1.2714 as a work piece steel and square copper electrode as a tool and dielectric flushing. The machining parameter selected are discharge current, pulse on time ,pulse off time , voltage , fluid pressure of the tool using Taguchi design approach analyzing the responses of EWR. The Taguchi’s method is used to formulate the 1|P a g e
Copyright@IDL-2017
IDL - International Digital Library Of Technology & Research Volume 1, Issue 5, May 2017
Available at: www.dbpublications.org
International e-Journal For Technology And Research-2017 Taguchi’s method is a powerful technique for the design of a high quality system. It provides not only,an efficient but also a systematic approach to optimize designs for performance and quality. Furthermore, Taguchi parameter design can reduce the fluctuation of system performance. A. This experiment is governed by the following steps are: Select process parameters to be evaluated. Select the appropriate orthogonal array and assign these parameters to the orthogonal array. Perform the experiments based on the arrangement of the orthogonal array. Analyze the experimental results using the signal to noise(S/N) ratio and analysis of variance (ANOVA).
experimental layout, ANOVA method is used to analysis the effect of process parameters on the machining characteristics and find the optimal process parameters of Electric Discharge Machining. 2.
LITERATURE SURVEY
Soni and Chakraverti (1997) compared the various performance measures of rotating electrode with the stationary electrode. The results concluded an improvement in MRR due to the better flushing action and sparking efficiency with little TWR but the surface finish was improved. Soni & Chakraverti (1994) introduced rotary disc for grooving operation on titanium alloy. The rotary electrode was placed above the work material. The difficulty of debris problem was encountered removal rate and arching occurs due to the accumulation of debris particle between the electrode and work piece. Zhang et al. (1997) Spark erosion with ultrasonic frequency using a DC power supply instead of the usual pulse power supply. The pulse discharge is produced by the relative motion between the tool and work piece simplifying the equipment and reducing its cost. It is easy to produce a combined technology which benefits from the virtues of USM and EDM. Khanra et al. attempted to develop a ZrB2-Cu composite that can be used as an EDM tool. They tested the tool by determination of responses like Material Removal Rate (MRR), Tool Wear Rate (TWR), Surface Roughness (SR) . Nipanikar optimized the process parameters of EDM by using Taguchi method. Optimization was carried out by taking into account the responses which include material removal rate MRR, TWR .
3.
B. Experimental design 1) Step1- Process parameters selection: Process parameters and their ranges were determined by the research paper. The parameters are identified for the test such as current, pulse-on time, pulse off time, flushing pressure, gap voltage. 2) Step 2- Orthogonal array selection: To select an appropriate orthogonal array for the experiments, on the basis of parameter selection and its levels. Here we have five parameters and three levels are selected. 3) Step 3- Conduct the experiment and Recording of responses: Twenty seven experimental runs were conducted as per the Taguchi’s L27 orthogonal array. The test runs were carried out at random to avoid a systematic error creeping into the experimental procedure. 4) Step 4- Analysis using ANOVA: The analysis of variance (ANOVA) is used to discuss the relative importance of all control factors on the machined material quality and also to determine which control factor has the most significant effect. Analysis of variance (ANOVA) is employed to find the optimal process parameter levels and to analyze the effect of these
METHODOLOGY
IDL - International Digital Library
2|P a g e
Copyright@IDL-2017
IDL - International Digital Library Of Technology & Research Volume 1, Issue 5, May 2017
Available at: www.dbpublications.org
International e-Journal For Technology And Research-2017 parameters on metal removal rate values and electrode wear rate. 4.
electronic balance. B. Selection of work piece DIN 1.2714 steel is an important tool and dies material, mainly because of its high strength, high hardness, and high wear resistance. It has a high strength due to that it cannot be easily machinable by conventional machining techniques. EDM is a nonconventional machining process that removes material by thermal erosion, such as melting and vaporization of material. To understand the machining characteristics of DIN 1.2714 steel by EDM is explored in this experimental study. DIN 1.2714 steel material is used in extrusion die, hot forging tools, dies for processing tin ,lead and zinc alloys. It is chemically composed of approximately 0.59 percent carbon, .83 percent manganese, 1.13 percent chromium, silicon 0.28, phosphorus 0.013,nickel 1.58, molybdenum 0.46and 0.7 percent vanadium. The hardening temperature of DIN 1.2714 steel is between 870 degrees Celsius and 900 degrees Celsius. DIN 1.2714 is a high carbon Alloy steel which achieves a high degree of hardness with compressive strength and abrasion resistance.
EXPERIMENTAL SETUP
The experiments were conducted using the Electric Discharge Machine, model ELECTRONICA ELECTRAPLUS PS 50ZNC (die sinking type) .The EDM consists of the following parts Dielectric reservoir, pump and circulation system, power generator and control unit ,working tank with work holding device , X-Y working table , the tool holder, the servo system for feeding the tool. Before experimentation, the work piece top and bottom faces were ground to a good surface finish using a surface grinding machine .The work piece was held on the machine table using a specially designed fixture as shown in fig1
5. TAGUCHI DESIGN Taguchi Method was proposed by Dr. G. Taguchi in the year 1950. Signal represents the effect on the average response while the noise is a measure of the influence on the deviation from the average response. The S/N ratio is the ratio of the mean (Signal) to the standard deviation (Noise). This ratio helps to identify the optimum level of process parameters. A high S/N ratio is desirable as the signal level is much higher than the random noise level that leads to best performance. The calculation of S/N ratio depends on the quality characteristics of the product or process to be optimized. The equation for calculating S/N ratios for “larger is better” and “smaller is better” .In the study, a three factor mixed level setup is chosen
Fig 1: Die –sinking EDM The work piece and tool were connected to the negative and positive terminals of the power supply, respectively. The dielectric fluid used here is kerosene. The time taken for machining was recorded. The experiments were conducted in the order of L27 orthogonal array. At the end of each experiment, the work piece was removed from the machine, washed, dried and weighed on an
IDL - International Digital Library
3|P a g e
Copyright@IDL-2017
IDL - International Digital Library Of Technology & Research Volume 1, Issue 5, May 2017
Available at: www.dbpublications.org
International e-Journal For Technology And Research-2017 with a total of twenty seven numbers of experiments to be conducted and hence the L27 was chosen. Table1 : Response parameter and control parameters with their levels Levels
50
15
90
150
0.5
0.0032
49.88
50
15
90
150
0.75
0.0048
46.21
60
9
45
150
0.25
0.0004
67.6
Control parameters
1
2
3
60
9
45
150
0.5
0.0004
66.3
Gap voltage (A)
50
60
70
60
9
45
150
0.75
0.0005
65.94
60
12
90
90
0.25
0.0044
46.93
60
12
90
90
0.5
0.0046
46.66
60
12
90
90
0.75
0.0045
46.83
60
15
15
120
0.25
0.0046
46.72
60
15
15
120
0.5
0.005
45.93
60
15
15
120
0.75
0.0062
44.1
70
9
90
120
0.25
0.0006
64.02
70
9
90
120
0.5
0.0007
62.31
70
9
90
120
0.75
0.0008
61.51
70
12
15
150
0.25
0.0012
57.83
70
12
15
150
0.5
0.0013
57.38
70
12
15
150
0.75
0.0013
57.26
70
15
45
90
0.25
0.0096
40.27
70
15
45
90
0.5
0.0098
40.14
70
15
45
90
0.5
0.0098
40.09
Discharge current (A) Pulse off time (µs)
9
12
15
15
45
90
Pulse on time (µs)
90
120
150
0.25
0.50
0.75
Fluid (kg/cm2)
pressure
6.RESULT AND DISCUSSIONS In the study. This experiment has 5 variables at 3 different settings. We conducted a Taguchi experiment with a L27 orthogonal array (27tests,5variables, 3 levels) and calculate S/N ratios corresponding to each experiment. The experiment design is shown in table 2. Table 2. Response table for EWR GV
PC
P off
P on
flushing pressure
TWR
S/N Ratio
50
9
15
90
0.25
0.0018
54.47
50
9
15
90
0.5
0.0016
55.56
50
9
15
90
0.75
0.0016
55.41
50
12
45
120
0.25
0.002
53.8
50
12
45
120
0.5
0.0042
47.37
50
12
45
120
0.75
0.0034
49.3
50
15
90
150
0.25
0.0027
51.08
IDL - International Digital Library
The S/N ratios for EWR are calculated as given in Equation.1. Taguchi method is used to analysis the result of response of machining parameter for smaller is better criteria .For smaller is better. S/N = -10 *log(Σ(Y2)/n) ……………(1) 4|P a g e
Copyright@IDL-2017
IDL - International Digital Library Of Technology & Research Volume 1, Issue 5, May 2017
Available at: www.dbpublications.org
International e-Journal For Technology And Research-2017 Where, yi = experimental value in the ith , n =number of replications .Where the S/N ratios calculated from observed values, yi represents the experimentally observed value of the ith experiment and n=1 is the repeated number of each experiment in L-27 is conducted.
Table 2: S/N Ratio table for EWR flushing Level GV PC Poff Pon pressure 1 2 3 Delta Rank
51.45 53.00 55.09 3.63 3
61.46 51.48 45.54 15.92 1
52.74 53.84 52.83 1.10 5
48.28 53.64 52.78 52.39 57.72 53.32 9.44 1.25 2 4
Table 3: Analysis of variance for S/N ratio Source DF Adj SS Adj MS F-Value P-Value GV PC Poff Pon flushing pr Error Lack-of-Fit Pure Error Total
Fig 3: Residual plots for S/N ratio
2 18.17 9.083 5.14 0.019 2 1242.49 621.247 351.70 0.000 2 1.80 0.900 0.51 0.610 2 482.72 241.358 136.64 0.000 2 15.74 7.872 4.46 0.029 16 28.26 1.766 15 28.26 1.884 1507.29 0.020 1 0.00 0.001 26 1792.83
Fig 4: Interaction plot for S/N ratio Fig 2: Main effect plot for S/N ratios (EWR)
IDL - International Digital Library
5|P a g e
Copyright@IDL-2017
IDL - International Digital Library Of Technology & Research Volume 1, Issue 5, May 2017
Available at: www.dbpublications.org
International e-Journal For Technology And Research-2017
7. CONCLUSION 1. The experimental results demonstrate that the discharge current is the main parameter along with pulse on time and pulse off time among five controllable factors (discharge current, voltage, pulse on time, pulse off time and fluid pressure) that influence the EWR in electric discharge machining of DIN 1.2714 steel. 2. The percentage contribution of current , pulse on time, pulse off time and flushing pressure and voltage are71.69%, 25.28%, 1.19%, 1.12% and 0.008% respectively. 3.The optimal parametric conditions are discharge current (15A),voltage (70V), pulse on time(150),pulse off time(90) and flushing pressure(0.25kg/cm2) to obtain maximum EWR
[2] Nipanikar, “Parameter Optimization of Electro Discharge Machining of AISI D3 Steel Material by using Taguchi Method”, Journal of Engineering Research and Studies, Vol. 3, No. 3, Pg. 7-10, 2012. [3] Kubade P.R., Jadhav V.S., “An Experimental Investigation of Electrode Wear Rate (EWR), Material Removal Rate (MRR) and Radial Overcut (ROC) in EDM of High Carbon-High Chromium Steel (AISI D3)”, International Journal of Engineering and Advanced Technology (IJEAT), Vol. 1, No. 5, Pg. 135-140, 2012. [4] Dhar S., Purohit R., “Mathematical Modeling and Statistical Analysis for Electric Discharge Machining (EDM) of Al-20% SI-CP cast metal matrix composite”, 2nd International Conference on Recent Advances in Composite Materials, IT-BHU, Varanasi, India, 2006. [5] Singh M.P., Kalra C.S., Singh S., “An Experimental Investigation of Radial Overcut during Machining of Al/Al2O3 MMC by Rotary EDM”, International Journal of Emerging Technology and Advanced Engineering, Vol. 3, No. 4, Pg. 617-619, 2013. [6] Soni H., Mishra T.K., Pradhan M.K., “MultiResponse Optimization of EDM Parameters by GreyPCA Method”, International Journal of Current Engineering and Technology, Vol. 3, No. 5, Pg 19411945, 2013. [7] Kiyak M. and Cakir O., Examination of machining parameters on surface roughness in EDM of tool steel, Journal of Materials Processing Technology, 191 (2007),141- 144.
8. REFERENCES [1] Khanra A K, Pathak L C and Godkhindi M M, “Application of new tool material for electrical discharge machining (EDM)”, Bull. Mater. Sci., Indian Academy of Sciences Vol. 32, No. 4, Pg. 401– 405, 2009.
IDL - International Digital Library
6|P a g e
Copyright@IDL-2017