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International Journal <strong>of</strong> Advanced Technology & Engineering Research (IJATER)<br />

OPTIMIZATION OF PROCESS PARAMETERS OF<br />

WIRE EDM USING ZINC-COATED BRASS WIRE<br />

Authors: 1 Manoj Malik, 2 Rakesh Kumar Yadav, 3 Nitesh Kumar, 4 Deepak Sharma, 5 Manoj<br />

Abstract<br />

Wire electrical discharge machining is a widely accepted<br />

non-traditional material removal <strong>process</strong> used to manufacture<br />

components with intricate pr<strong>of</strong>iles. In <strong>wire</strong> EDM, the<br />

conductive materials are machined with a series <strong>of</strong> electrical<br />

discharges (sparks) that are produced between an accurately<br />

positioned moving <strong>wire</strong> (the electrode) and the work piece.<br />

High frequency pulses <strong>of</strong> alternating or direct current is discharged<br />

from the <strong>wire</strong> to the work piece with a very small<br />

spark gap through insulated dielectric fluid (water). In this<br />

paper there are three factors has been taken for <strong>optimization</strong><br />

i.e. Metal removal rate, Electrode wear rate, and Surface<br />

roughness <strong>using</strong> Zinc-coated brass <strong>wire</strong>.<br />

Keywords: - WEDM, Metal removal rate, surface finish, taguchi<br />

method, Electrode wear rate.<br />

I. Introduction<br />

Recently, non-conventional machining is well established<br />

used by component manufacturer as a manufacturing<br />

method. Non-conventional is not involved with the high<br />

force, without tool ware and the most things for the environment<br />

it is a green <strong>process</strong>. The <strong>process</strong> is not deal with<br />

the metal chip and only water is used as an electrode. Wire<br />

electrical discharge machining (<strong>wire</strong>-EDM), EDM die sinking,<br />

water jet cutting and laser cutting are the most regularly<br />

used by the manufacturer. Wire-EDM as a precision cutting<br />

technology is possible to fabricate from a small range <strong>of</strong><br />

product until a large size <strong>of</strong> component. All type <strong>of</strong> good<br />

conductivity metal such as mild steel and copper are possible<br />

to be cut <strong>using</strong> <strong>wire</strong>-EDM. However, machine setting varies<br />

for each type <strong>of</strong> metals. So, certain <strong>parameters</strong> need to be<br />

clearly defined for each <strong>of</strong> materials. In <strong>wire</strong>-EDM, to cut<br />

two types <strong>of</strong> material in one time or parallel cutting is a big<br />

challenge. Machine setting for both <strong>of</strong> the materials need to<br />

be considered and optimized. Besides that, the machine setting<br />

is also base on the curve or pr<strong>of</strong>ile to be cut.<br />

The setting is easy tuned for a straight line and become more<br />

difficult for the curve or part which is involving an angle.<br />

Limitation <strong>of</strong> cutting speed is applied by Sanchez et. al.<br />

(2007) in order to minimize the errors at different zones <strong>of</strong><br />

the corner. Ninety degree angle is the most difficult section<br />

to be cut by <strong>wire</strong>-EDM because <strong>of</strong> the dramatically<br />

direction changing. Wire electrical discharge machining<br />

<strong>process</strong> is a highly complex, time varying & stochastic<br />

<strong>process</strong>. The <strong>process</strong> output is affected by large no <strong>of</strong><br />

input variables. Therefore a suitable selection <strong>of</strong> input variables<br />

for the <strong>wire</strong> electrical discharge machining (WEDM)<br />

<strong>process</strong> relies heavily on the operators technology & experience<br />

because <strong>of</strong> their numerous & diverse range. WEDM is<br />

extensively used in machining <strong>of</strong> conductive materials when<br />

precision is <strong>of</strong> prime importance. Rough cutting operation in<br />

<strong>wire</strong> EDM is treated as challenging one because improvement<br />

<strong>of</strong> more than one performance measures viz. Metal<br />

removal rate (MRR), surface finish & cutting width are<br />

sought to obtain precision work. In this paper an approach to<br />

determine <strong>parameters</strong> setting is proposed. Using taguchi’s<br />

parameter design, significant machining <strong>parameters</strong> affecting<br />

the performance measures are identified as pulse peak<br />

current, pulse on time, and duty factor. The effect <strong>of</strong> each<br />

control factor on the performance measure is studied individually<br />

<strong>using</strong> the plots <strong>of</strong> signal to noise ratio. The study<br />

demonstrates that the WEDM <strong>process</strong> <strong>parameters</strong> can be<br />

adjusted so as to achieve better metal removal<br />

rate, surface finish, electrode wear rate.<br />

Fig. 1 Wire EDM Set-up<br />

Table1<br />

PROCESS PARAMETERS OF MICRO WIRE EDM PROCESS<br />

S. PARAMETERS RANGE<br />

ISSN No: 2250-3536 Volume 2, Issue 4, July 2012 127


International Journal <strong>of</strong> Advanced Technology & Engineering Research (IJATER)<br />

No.<br />

1 Frequency 0-200 KHz<br />

2 Pulse width 1-10 μs<br />

3 gap % <strong>of</strong> voltage 60-100%<br />

4 gain 0-100<br />

5 pulse peak current 40A<br />

6 output voltage 60-250V<br />

7 Dwell time 0-20s<br />

8 polarity +/-<br />

9 hole diameter 0.05 -1 mm<br />

10 spindle speed 100-1000 rev/min<br />

II. LITERATURE REVIEW<br />

The material removal mechanism <strong>of</strong> WEDM is very similar<br />

to the conventional EDM <strong>process</strong> involving the erosion effect<br />

produced by the electrical discharges (sparks). In<br />

WEDM, material is eroded from the work piece by a series<br />

<strong>of</strong> discrete sparks occurring between the work piece and the<br />

<strong>wire</strong> separated by a stream <strong>of</strong> dielectric fluid, which is continuously<br />

fed to the machining zone. However, today's<br />

WEDM <strong>process</strong> is commonly conducted on work pieces that<br />

are totally submerged in a tank filled with dielectric fluid.<br />

Such a submerged method <strong>of</strong> WEDM promotes temperature<br />

stabilisation and efficient flushing especially in cases where<br />

the work piece has varying thickness. The WEDM <strong>process</strong><br />

makes use <strong>of</strong> electrical energy generating a channel <strong>of</strong> plasma<br />

between the cathode and anode, and turns it into thermal<br />

energy at a temperature in the range <strong>of</strong> 8000-12,000 OC or<br />

as high as 20,000 OC initializing a substantial amount <strong>of</strong><br />

heating and melting <strong>of</strong> material on the surface <strong>of</strong> each pole.<br />

When the pulsating direct current power supply occurring<br />

between 20,000 and 30,000 Hz is turned <strong>of</strong>f, the plasma<br />

channel breaks down. This causes a sudden reduction in the<br />

temperature allowing the circulating dielectric fluid to implore<br />

the plasma channel and flush the molten particles from<br />

the pole Surfaces in the form <strong>of</strong> microscopic debris. While<br />

the material removal mechanisms <strong>of</strong> EDM and WEDM are<br />

similar, their functional characteristics are not identical.<br />

WEDM uses a thin <strong>wire</strong> continuously feeding through the<br />

work piece by a micro<strong>process</strong>or, which enable parts <strong>of</strong> complex<br />

shapes to be machined with exceptional high accuracy.<br />

A varying degree <strong>of</strong> taper ranging from lSO for a 100 mm<br />

thick to 30" for a 400 mm thick work piece can also be obtained<br />

on the cut surface. The micro<strong>process</strong>or also constantly<br />

maintains the gap between the <strong>wire</strong> and the wok piece,<br />

which varies from 0.025 to 0.05 mm. WEDM, eliminates the<br />

need for elaborate pre-shaped electrodes, which are commonly<br />

required in EDM to perform the roughing and finishing<br />

operations. In the case <strong>of</strong> WEDM, the <strong>wire</strong> has to make<br />

several machining passes along the pr<strong>of</strong>ile to be machined to<br />

attain the required dimensional accuracy and surface finish<br />

(SF) quality.<br />

Kunieda and Furudate tested the feasibility <strong>of</strong> conducting<br />

dry WEDM to improve the accuracy <strong>of</strong> the finishing operations,<br />

which was conducted in a gas atmosphere without<br />

<strong>using</strong> dielectric fluid. In addition, WEDM uses deionised<br />

water instead <strong>of</strong> hydrocarbon oil as the dielectric fluid and<br />

contains it within the sparking zone. The deionised water is<br />

not suitable for conventional EDM as it causes rapid electrode<br />

wear, but its low viscosity and rapid cooling rate make<br />

it ideal for WEDM.<br />

III. EXPERIMENTAL SETUP<br />

3.1 GREY BASED TAGUCHI METHOD:-<br />

Genichi Taguchi, a Japanese scientist, developed a technique<br />

based on OA <strong>of</strong> experiments. This technique has been<br />

widely used in different fields <strong>of</strong> engineering to optimize the<br />

<strong>process</strong> <strong>parameters</strong>. The integration <strong>of</strong> DOE with parametric<br />

<strong>optimization</strong> <strong>of</strong> <strong>process</strong> can be achieved in the Taguchi<br />

method. An OA provides a set <strong>of</strong> well-balanced experiments,<br />

and Taguchi’s signal-to-noise. (S/N) ratios, which are<br />

logarithmic functions <strong>of</strong> the desired output, serve as objective<br />

functions for <strong>optimization</strong>. It helps to learn the whole<br />

parameter space with a small number (minimum experimental<br />

runs) <strong>of</strong> experiments. OA and S/N ratios are used to study<br />

the effects <strong>of</strong> control factors and noise factors and to determine<br />

the best quality characteristics for particular applications.<br />

Fig.2. Principle <strong>of</strong> <strong>wire</strong> EDM<br />

The optimal <strong>process</strong> <strong>parameters</strong> obtained from the Taguchi<br />

method are insensitive to the variation <strong>of</strong> environmental<br />

conditions and other noise factors. However, originally, Taguchi<br />

method was designed to optimize single-performance<br />

characteristics. Optimization <strong>of</strong> multiple performance characteristics<br />

is not straightforward and much more complicated<br />

than that <strong>of</strong> single-performance characteristics. To solve the<br />

multiple performance characteristics problems, the Taguchi<br />

ISSN No: 2250-3536 Volume 2, Issue 4, July 2012 128


International Journal <strong>of</strong> Advanced Technology & Engineering Research (IJATER)<br />

method is coupled with grey relational analysis. Grey relational<br />

analysis was first proposed by Deng in 1982 to fulfil<br />

the crucial mathematical criteria for dealing with poor, incomplete,<br />

and uncertain system This grey-based Taguchi<br />

technique has been widely used indifferent fields <strong>of</strong> engineering<br />

to solve multi-response <strong>optimization</strong> problems.<br />

The taguchi method can be obtained by step by step procedure<br />

as shown in fig. 3 below:<br />

Table 2. Electrical discharge machining condition<br />

Work condition<br />

Electrode<br />

Work piece<br />

Voltage<br />

Peak current<br />

Pulse duration<br />

Description<br />

Brass <strong>wire</strong> with <strong>zinc</strong> coated, diameter 9 mm,<br />

Length 70 mm<br />

Tungsten Carbide ceramic, square shape<br />

(100x100x7mm)<br />

120 to 200 V<br />

8 to 64 A<br />

1.6 to 50 μs<br />

Interval time 3.2 to 800<br />

Dielectric fluid Kerosene<br />

3.2 DESIGN OF EXPERIMENT:<br />

As per the taguchi quality design concept L9 orthogonal<br />

array table was arbitrarily chosen to study <strong>optimization</strong><br />

<strong>process</strong>.<br />

1. Three control factors were chosen each at 3 levels<br />

A- Pulse on time (μs)<br />

B- Duty factor = (pulse on time/(pulse on time + pulse <strong>of</strong><br />

time))<br />

C- Pulse peak current (A)<br />

2. Three response <strong>parameters</strong> were measured<br />

(I) Metal removal rate i.e. MRR (g/min)<br />

(II) Electrode wear rate i.e. EWR (%)<br />

(III)Surface roughness i.e. SR (μm)<br />

Table 3. Machining <strong>parameters</strong> & their levels<br />

Fig. 3. Grey-based taguchi method procedure<br />

In this paper, the cutting <strong>of</strong> Tungsten Carbide ceramic <strong>using</strong><br />

electro-discharge machining (EDM) with a graphite electrode<br />

by <strong>using</strong> Taguchi methodology has been reported by<br />

Radzi et al. The Taguchi method is used to formulate the<br />

experimental layout, to analyse the effect <strong>of</strong> each parameter<br />

on the machining characteristics, and to predict the optimal<br />

choice for each EDM parameter such as peak current, voltage,<br />

pulse duration and interval time. It is found that these<br />

<strong>parameters</strong> have a significant influence on machining characteristic<br />

such as metal removal rate (MRR), electrode wear<br />

rate (EWR) and surface roughness (SR). The analysis <strong>of</strong> the<br />

Taguchi method reveals that, in general the peak current<br />

significantly affects the EWR and SR, while, the pulse duration<br />

mainly affects the MRR.<br />

Symbol Parameter Unit Level<br />

1<br />

Level<br />

2<br />

Level<br />

3<br />

A Pulse on μs 5 100 200<br />

time<br />

B Duty factor - 0.2 0.4 0.6<br />

C<br />

Pulse peak<br />

current<br />

3.3 EXPERIMENTAL RESULTS:<br />

A 1 5 7<br />

The experimental results obtained in EDM are given below:<br />

Table 3. Experimental results <strong>of</strong> <strong>process</strong><br />

A B C MRR EWR RA<br />

1 1 1 0.0024 29.896 3.01<br />

1 2 2 0.0058 5.253 2.78<br />

ISSN No: 2250-3536 Volume 2, Issue 4, July 2012 129


International Journal <strong>of</strong> Advanced Technology & Engineering Research (IJATER)<br />

1 3 3 0.0097 4.897 3.45<br />

2 1 2 0.0066 2.345 2.95<br />

2 2 3 0.0087 0.765 2.98<br />

2 3 1 0.0029 28.906 2.5<br />

3 1 3 0.59 0.234 2.12<br />

3 2 1 0.0031 28.865 2.56<br />

3 3 2 0.0037 0.789 2.01<br />

V. REFERANCES<br />

IV. CONCLUSION<br />

1. It can be seen from the graph 1 for MRR to b maximum<br />

factor A, B has to be at level 2 & factor c has to<br />

be at level 3.<br />

2. Pulse peak current is the most critical factor affecting<br />

MRR& duty factor is the least significant parameter.<br />

3. For minimum EWR factor A, C has to be at level 3 &<br />

factor B has to be at level 1.<br />

4. Pulse peak current is the most critical factor affecting<br />

EWR& duty factor is the least significant parameter.<br />

5. For minimum surface roughness factor A, B has to be<br />

at level 3 & factor C has to be at level 2.<br />

6. Pulse on time is the most critical factor affecting surface<br />

roughness & duty factor is the least significant parameter.<br />

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Biographies<br />

1 MANOJ MALIK (MAIN AUTHOR) B.Tech. and<br />

M.Tech. from Maharishi Dayanand University, Rohtak. His<br />

research areas include Manufacturing and Automation field.<br />

manojkumarmalik1984@gmail.com<br />

2 RAKESH KUMAR YADAV, Assistant Pr<strong>of</strong>essor, Al-<br />

Falah School <strong>of</strong> Engineering & Technology, Faridabad<br />

rkymech@gmail.com<br />

3 NITESH KUMAR, Assistant Pr<strong>of</strong>essor, Rawal Institute <strong>of</strong><br />

Engineering & Technology, Faridabad<br />

nitesh.bitspilani@gmail.com<br />

4 HARICHAND, Assistant Pr<strong>of</strong>essor, Rawal Institute <strong>of</strong><br />

Engineering & Technology, Faridabad<br />

harichand88@gmail.com<br />

5 DEEPAK SHARMA, Assistant Pr<strong>of</strong>essor, Rawal Institute<br />

<strong>of</strong> Engineering & Technology, Faridabad<br />

6 MANOJ, Lecturer, Rawal Institute <strong>of</strong> Engineering & Technology,<br />

Faridabad.<br />

mrdudeja@gmail.com<br />

ISSN No: 2250-3536 Volume 2, Issue 4, July 2012 130

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