Modeling of Wire Electrical Discharge Machining ... - IJETAE

International Journal of Emerging Technology and Advanced Engineering 

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012) 

Modeling of Wire Electrical Discharge Machining Parameters 

Using Titanium Alloy (Ti-6AL-4V) 

Basil Kuriachen 1 , Dr. Josephkunju Paul 2 , Dr.Jose Mathew 3 

1 Research Scholar, Department of Mechanical Engineering, National Institute of Technology Calicut 

Kozhikode-673601, India 

2 Professor and HOD, Department of mechanical Engineering, MA College of Engineering Kothamangalam, India 

3 Professor, Department of Mechanical Engineering, National Institute of Technology Calicut 

Abstract— Wire electro discharge machining (WEDM) is a 

modification of electro discharge machining (EDM) which has 

been widely used for long time for cutting punches and dies, 

shaped pockets and other machine parts of electrically 

conducting work materials. Technology of the WEDM process 

is based on the conventional EDM sparking phenomenon, 

utilizing the widely accepted non contact technique of 

material removal with a difference that spark is generated at 

the wire and work piece gap. Evolution of WEDM made 

drastic changes in the area of precision machining with 

highest degree of dimensional accuracy and surface finish. In 

this paper, two level full factorial techniques were used for 

modelling and predicting the surface roughness in WEDM of 

titanium (Ti-6Al-4V) alloy. Surface roughness was taken as a 

response variable measured after machining and pulse ON 

time, pulse OFF time, voltage and dielectric flushing pressure 

were taken as input parameters. The level of importance of 

the WEDM cutting parameters on the surface roughness was 

determined by using the analysis of variance method 

(ANOVA). A mathematical relation between the workpiece 

surface roughness and WEDM cutting parameters was 

established. This mathematical model may be used for 

evaluating the surface roughness without performing any 

experiments. The predicted values of surface roughness by the 

mathematical model were compared with the experimental 

values. It is observed that the predicted results agree with the 

experimental values within an error of 7 %. 

Keywords— Surface roughness, factorial design, WEDM, 

Titanium (Grade 5), DOE 

Kozhikode-673601, India 

1 basilkuriachen@gmail.com 

2 josephkunju.paul@gmail.com 

3 josmat@nitc.ac.in 

377 

I. INTRODUCTION 

WEDM is one of the non-traditional processes which is 

accepted globally to machine high strength to weight ratio 

materials mainly employed for nuclear and aerospace 

industries. This (WEDM) is one of the main applications of 

the traditional electrical discharge machining (EDM). EDM 

machining was first discovered by the English scientist 

Joseph Priestly in 1770, but its advantages were utilized 

completely only in the year 1943 by the Russian scientists 

and it was commercially developed in the year 1970. In the 

mid of 1980s this technique was used in machine tools to 

machine electrically conducting materials. WEDM utilizes 

a continuously travelling wire electrode made of thin 

copper, brass or tungsten or coated wire of diameter 0.05 – 

0.3 mm [1]. A dielectric fluid is forced into the machining 

zone to improve the effectiveness as well as to carry away 

the debris so that it reduces the chances of short circuit 

between wire electrode and the work piece. Nowadays, in 

order to achieve better performance, the work piece and the 

tool are submerged in the dielectric fluid. Most commonly 

used dielectric fluids are kerosene and de ionized water [2]. 

The data base to select the correct parameter setting for 

newly developed materials is not readily available. The 

machine manufacturers provide the information only for 

the commonly used materials. So the databases provided by 

the manufacturers are not enough to meet the present needs 

of modern industries [3]. 

This study aims to examine the influence of four 

important parameters viz. ‗pulse on time‘, ‗pulse off time‘, 

‗voltage‘ and ‗dielectric pressure‘ on surface roughness in



WEDM of Ti-6Al-4V. The various parameters were 

selected using design of experiments method. 

II. LITERATURE REVIEW 

There are a number of published works that reveal the 

influence of WEDM parameters on the surface roughness 

of different materials. Y.S. Liao found that surface 

roughness is most affected by the pulse on time [5]. The 

WEDM parameters are generally classified into two groups 

namely electrical and non electrical. [6]. S.S. Mahapatra 

and Amar Patnaik have investigated the effect of various 

parameters and found that current, pulse duration and 

dielectric pressure play most significant role in surface 

finish [7]. U.Esme et.al observed that increase in pulse 

duration, voltage and wire speed increase the surface 

roughness whereas increase in flushing pressure of 

dielectric fluid decrease the surface roughness [8]. The 

investigations made by J.T Hung et.al revealed that pulse 

on time is one of the significant factors that influence 

surface roughness [9]. The previous researchers established 

that pulse duration, voltage, and dielectric pressure are the 

desired combination to control the surface finish [1]. 

Ramakrishnan et al. described the multi objective 

optimization of the WEDM process using parametric 

design of Taguchi methodology [11]. Fuzhu Han et.al 

found that surface roughness can be improved by 

decreasing both pulse duration and discharge current [10]. 

Although lot of investigations were done on the influence 

of various WEDM parameters on surface roughness, till 

date no investigation was conducted on the influence of 

pulse on time, pulse off time, voltage and dielectric 

pressure on WEDM of Ti-6Al-4V using DOE. This 

experimental study reveals the influence of pulse on time, 

pulse off time, voltage and dielectric pressure and its 

interactions on the surface roughness in WEDM of Ti-6Al- 

4V alloy. 

FIGURE .1 DETAILS OF WEDM SETUP. 

378 

III. EXPERIMENTAL SET UP 

The experimental set up adopted for present study is 

given in figure 2. The WEDM experiments were conducted 

in Electronica ultra cut s1 machine using 0.25 mm brass 

wire as the tool electrode. ‗Pulse on time‘, ‗pulse off time‘, 

‗voltage‘ and ‗dielectric pressure‘ are the four WEDM 

parameters that were selected for investigations. In this 

experimental study two level full factorial experiment is 

adopted because this gives all possible combinations of 

machine parameters. All other machine parameters were 

kept constant during the time of experiment. 

IV. EXPERIMENTAL DESIGN BASED ON DOE 

A full factorial design with all factors at two levels 

provides the estimation of all the required parameter 

combinations. Altogether sixteen experiments and two 

conformation tests were conducted. For the analysis of the 

experiments 10% confidence level is used. 

FIGURE.2 ELECTRONICA ULTRACUT S1 WEDM 5-AXES 

ANNOVA table helped to find out the significant factors 

and to establish the mathematical relationship between the 

surface roughness and machining parameters. 

TABLE I 

MACHINING PARAMETERS AND LEVELS 

Factor Parameters Level 1 Level 2 

A Pulse on time (μS) 20 25 

B Pluse off time (μS) 44 50 

C Voltage (V) 25 30 

D 

Dielectric pressure 

(kgf/cm 2 ) 

10 15



V. RESULTS AND DISCUSSIONS 

This section discusses the influence of the process 

parameters on the surface roughness. The main objective of 

this discussion is to assess the variation of surface 

roughness with respect to the change in the process 

parameters. The various machining parameters in two 

levels and corresponding results of surface roughness 

(average of three readings) are tabulated in Table 2. 

No 

TABLE II 

EXPERIMENTAL DESIGN AND RESULTS 

Voltage 

(V) 

Dielectric 

pressure 

(kgf/cm 2 ) 

Pulse 

on 

time 

(μS) 

Pulse 

off 

time 

(μS) 

Ra 

(μm) 

1 25 10 20 44 3.534 

2 30 10 20 44 3.544 

3 25 15 20 44 3.331 

4 30 15 20 44 3.348 

5 25 10 25 44 4.227 

6 30 10 25 44 4.285 

7 25 15 25 44 3.628 

8 30 15 25 44 4.009 

9 25 10 20 50 3.635 

10 30 10 20 50 3.447 

11 25 15 20 50 3.624 

12 30 15 20 50 3.364 

13 25 10 25 50 3.907 

14 30 10 25 50 4.023 

15 25 15 25 50 3.384 

16 30 15 25 50 4.283 

17 28 13 23 47 3.821 

18 26 11 21 45 3.388 

379 

The ANNOVA table of surface roughness (Ra) showed 

that two individual factors and one interaction affect the 

surface roughness. The probability values (Prob>F) are less 

than 0.05 for pulse on time, dielectric pressure(WP) and the 

interaction between the voltage and pulse on time. The 

most important factor which affects the surface roughness 

is pulse on time. The relation between the various 

parameters and surface roughness are given in the main 

effect plot viz. figure (3a), figure (3b) and figure (3c). 

FIGURE 3A 

FIGURE 3B 

FIGURE 3C 

FIGURE. 3 INTERACTIONS OF VARIOUS FACTORS WITH 

SURFACE ROUGHNESS



It is evident from figure (3a) that the surface roughness 

decreases with increase in dielectric pressure, whereas 

figure (3b) reveals that the surface roughness increases 

with increase in pulse on time. Figure (3c) gives the 

variation of surface roughness with voltage corresponding 

to minimum and maximum values of pulse on time. It can 

be noticed from the figure that corresponding to minimum 

value of pulse on time the surface roughness decreases with 

increase in voltage, whereas the surface roughness 

increases with increase in voltage corresponding to 

maximum value of pulse on time. 

When the pulse on time is maximum and the voltage 

increase from 25 v to 30 v, the surface roughness also 

increases. To achieve minimum surface roughness (Ra), the 

pulse on time, voltage and dielectric pressure should be set 

at 20 µs, 30 V and 15 kgf/cm 2 respectively. The effect of 

these factors on surface roughness is evident from the ‗3 D 

interaction graph‘ depicted in fig. (4). A contour plot of 

surface roughness connecting pulse on time and voltage is 

given in fig. (5). On the basis of the experimental 

investigations, an empirical relationship for surface 

roughness connecting voltage, dielectric pressure and pulse 

on time is established, which is given below 

FIGURE.4 SURFACE PLOT FOR SURFACE ROUGHNESS. 

FIGURE.5 CONTOUR PLOT FOR SURFACE ROUGHNESS. 

380 

Ra = - 21.54350 + (0.79120 X Voltage) + (2.71630 X 

dielectric pressure) + (1.27310 X pulse on time) - 

(0.094980 X Voltage X dielectric pressure) – (0.039800 X 

Voltage X pulse on time) -(0.13526 X dielectric pressure 

X pulse on time) + (4.68400E-003 X Voltage X dielectric 

pressure X pulse on time) 

VI. COMPARISON OF CONFORMATION TEST 

RESULTS WITH PREDICTED VALUES. 

Two conformation runs were conducted in order to 

measure the reliability of optimization solutions obtained 

from the analysis.The comparison of test results between 

the therotical prediction and conformation test results were 

the final consideration that will determine whether the 

optimum parameters predicted are within the allowable 

range. The margin of error from prediction and 

experimental results was obtained below 7%. Table 3 

shows the comparison of the test results with the predicted 

values. 

TABLE IIIIV 

COMPARISON OF THE TEST RESULTS WITH THE THEROTICAL 

PREDICTION. 

No. of 

conformation 

Runs 

Predicted 

values using 

the 

mathematical 

model 

Conformation 

test results 

% of 

Error 

1 3.77109 3.821 1.32 

2 3.63406 3.388 6.76 

VII. CONCLUSION 

In this study, the machining of Ti-6Al-4V alloy‘s 

performance in wire electrical discharge machining is 

explored by using two level full factorial experiment. 

Design expert was adopted in this study to determine the 

optimum condition of machining parameters and the 

significance of each parameter on the performance of 

machining charectristics.



The following conclusions are drawn based on the 

investigations. 

1. The pulse on time , dielectric pressure, the interaction of 

voltage and pulse on time are significant parameters which 

affect the surface roughness. 

2. Minimum surface roughness can be obtained by adopting 

a low value of pulse on time (20 µs) and a high value of 

dielectric pressure (15 kgf/cm 2 ). 

3. Improper setting of pulse on time and pulse off time can 

lead to wire breakage which in turn lead to increase in 

machining time. 

4. A mathematical model is established to predict the value 

of surface roughness. 

5. The marginal error obtained by the comparision of the 

predicted results with the conformation test was less than 

7%. 

REFERENCES 

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of the art in wire electrical discharge machining (WEDM)‖ 

International Journal of Machine Tools & Manufacture 44 

(2004) 1247–1259. 

[2] Manufacuring science second edition by Amitabha Ghosh 

and Asok Kumar Mallik, Second Edition. 

[3] Scott F. Miller, Chen-C. Kao, Albert J. Shih, Jun Qu, 

―Investigation of wire electrical discharge machining of thin 

cross-sections and compliant mechanisms‖, International 

Journal of Machine Tools & Manufacture 45 (2005) 1717– 

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[4] Fuzhu Han, Jun Jiang, Dingwen Yu, ―Influence of discharge 

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[5] Y.S. Liao, J.T. Huang, Y.H. Chen, ―A study to achieve a 

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[6] Y.S. Liao, J.T. Huang, Y.H. Chen, ―A study to achieve a 

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[7] Yan, B. H., Wang, C. C., Liu, W. D. and Huang F. Y. 

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