optimization of process parameters of wire edm using zinc ... - ijater

International Journal of Advanced Technology & Engineering Research (IJATER)
OPTIMIZATION OF PROCESS PARAMETERS OF
WIRE EDM USING ZINC-COATED BRASS WIRE
Authors: 1 Manoj Malik, 2 Rakesh Kumar Yadav, 3 Nitesh Kumar, 4 Deepak Sharma, 5 Manoj
Abstract
Wire electrical discharge machining is a widely accepted
non-traditional material removal process used to manufacture
components with intricate profiles. In wire EDM, the
conductive materials are machined with a series of electrical
discharges (sparks) that are produced between an accurately
positioned moving wire (the electrode) and the work piece.
High frequency pulses of alternating or direct current is discharged
from the wire to the work piece with a very small
spark gap through insulated dielectric fluid (water). In this
paper there are three factors has been taken for optimization
i.e. Metal removal rate, Electrode wear rate, and Surface
roughness using Zinc-coated brass wire.
Keywords: - WEDM, Metal removal rate, surface finish, taguchi
method, Electrode wear rate.
I. Introduction
Recently, non-conventional machining is well established
used by component manufacturer as a manufacturing
method. Non-conventional is not involved with the high
force, without tool ware and the most things for the environment
it is a green process. The process is not deal with
the metal chip and only water is used as an electrode. Wire
electrical discharge machining (wire-EDM), EDM die sinking,
water jet cutting and laser cutting are the most regularly
used by the manufacturer. Wire-EDM as a precision cutting
technology is possible to fabricate from a small range of
product until a large size of component. All type of good
conductivity metal such as mild steel and copper are possible
to be cut using wire-EDM. However, machine setting varies
for each type of metals. So, certain parameters need to be
clearly defined for each of materials. In wire-EDM, to cut
two types of material in one time or parallel cutting is a big
challenge. Machine setting for both of the materials need to
be considered and optimized. Besides that, the machine setting
is also base on the curve or profile to be cut.
The setting is easy tuned for a straight line and become more
difficult for the curve or part which is involving an angle.
Limitation of cutting speed is applied by Sanchez et. al.
(2007) in order to minimize the errors at different zones of
the corner. Ninety degree angle is the most difficult section
to be cut by wire-EDM because of the dramatically
direction changing. Wire electrical discharge machining
process is a highly complex, time varying & stochastic
process. The process output is affected by large no of
input variables. Therefore a suitable selection of input variables
for the wire electrical discharge machining (WEDM)
process relies heavily on the operators technology & experience
because of their numerous & diverse range. WEDM is
extensively used in machining of conductive materials when
precision is of prime importance. Rough cutting operation in
wire EDM is treated as challenging one because improvement
of more than one performance measures viz. Metal
removal rate (MRR), surface finish & cutting width are
sought to obtain precision work. In this paper an approach to
determine parameters setting is proposed. Using taguchi’s
parameter design, significant machining parameters affecting
the performance measures are identified as pulse peak
current, pulse on time, and duty factor. The effect of each
control factor on the performance measure is studied individually
using the plots of signal to noise ratio. The study
demonstrates that the WEDM process parameters can be
adjusted so as to achieve better metal removal
rate, surface finish, electrode wear rate.
Fig. 1 Wire EDM Set-up
Table1
PROCESS PARAMETERS OF MICRO WIRE EDM PROCESS
S. PARAMETERS RANGE
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International Journal of Advanced Technology & Engineering Research (IJATER)
No.
1 Frequency 0-200 KHz
2 Pulse width 1-10 μs
3 gap % of voltage 60-100%
4 gain 0-100
5 pulse peak current 40A
6 output voltage 60-250V
7 Dwell time 0-20s
8 polarity +/-
9 hole diameter 0.05 -1 mm
10 spindle speed 100-1000 rev/min
II. LITERATURE REVIEW
The material removal mechanism of WEDM is very similar
to the conventional EDM process involving the erosion effect
produced by the electrical discharges (sparks). In
WEDM, material is eroded from the work piece by a series
of discrete sparks occurring between the work piece and the
wire separated by a stream of dielectric fluid, which is continuously
fed to the machining zone. However, today's
WEDM process is commonly conducted on work pieces that
are totally submerged in a tank filled with dielectric fluid.
Such a submerged method of WEDM promotes temperature
stabilisation and efficient flushing especially in cases where
the work piece has varying thickness. The WEDM process
makes use of electrical energy generating a channel of plasma
between the cathode and anode, and turns it into thermal
energy at a temperature in the range of 8000-12,000 OC or
as high as 20,000 OC initializing a substantial amount of
heating and melting of material on the surface of each pole.
When the pulsating direct current power supply occurring
between 20,000 and 30,000 Hz is turned off, the plasma
channel breaks down. This causes a sudden reduction in the
temperature allowing the circulating dielectric fluid to implore
the plasma channel and flush the molten particles from
the pole Surfaces in the form of microscopic debris. While
the material removal mechanisms of EDM and WEDM are
similar, their functional characteristics are not identical.
WEDM uses a thin wire continuously feeding through the
work piece by a microprocessor, which enable parts of complex
shapes to be machined with exceptional high accuracy.
A varying degree of taper ranging from lSO for a 100 mm
thick to 30" for a 400 mm thick work piece can also be obtained
on the cut surface. The microprocessor also constantly
maintains the gap between the wire and the wok piece,
which varies from 0.025 to 0.05 mm. WEDM, eliminates the
need for elaborate pre-shaped electrodes, which are commonly
required in EDM to perform the roughing and finishing
operations. In the case of WEDM, the wire has to make
several machining passes along the profile to be machined to
attain the required dimensional accuracy and surface finish
(SF) quality.
Kunieda and Furudate tested the feasibility of conducting
dry WEDM to improve the accuracy of the finishing operations,
which was conducted in a gas atmosphere without
using dielectric fluid. In addition, WEDM uses deionised
water instead of hydrocarbon oil as the dielectric fluid and
contains it within the sparking zone. The deionised water is
not suitable for conventional EDM as it causes rapid electrode
wear, but its low viscosity and rapid cooling rate make
it ideal for WEDM.
III. EXPERIMENTAL SETUP
3.1 GREY BASED TAGUCHI METHOD:-
Genichi Taguchi, a Japanese scientist, developed a technique
based on OA of experiments. This technique has been
widely used in different fields of engineering to optimize the
process parameters. The integration of DOE with parametric
optimization of process can be achieved in the Taguchi
method. An OA provides a set of well-balanced experiments,
and Taguchi’s signal-to-noise. (S/N) ratios, which are
logarithmic functions of the desired output, serve as objective
functions for optimization. It helps to learn the whole
parameter space with a small number (minimum experimental
runs) of experiments. OA and S/N ratios are used to study
the effects of control factors and noise factors and to determine
the best quality characteristics for particular applications.
Fig.2. Principle of wire EDM
The optimal process parameters obtained from the Taguchi
method are insensitive to the variation of environmental
conditions and other noise factors. However, originally, Taguchi
method was designed to optimize single-performance
characteristics. Optimization of multiple performance characteristics
is not straightforward and much more complicated
than that of single-performance characteristics. To solve the
multiple performance characteristics problems, the Taguchi
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International Journal of Advanced Technology & Engineering Research (IJATER)
method is coupled with grey relational analysis. Grey relational
analysis was first proposed by Deng in 1982 to fulfil
the crucial mathematical criteria for dealing with poor, incomplete,
and uncertain system This grey-based Taguchi
technique has been widely used indifferent fields of engineering
to solve multi-response optimization problems.
The taguchi method can be obtained by step by step procedure
as shown in fig. 3 below:
Table 2. Electrical discharge machining condition
Work condition
Electrode
Work piece
Voltage
Peak current
Pulse duration
Description
Brass wire with zinc coated, diameter 9 mm,
Length 70 mm
Tungsten Carbide ceramic, square shape
(100x100x7mm)
120 to 200 V
8 to 64 A
1.6 to 50 μs
Interval time 3.2 to 800
Dielectric fluid Kerosene
3.2 DESIGN OF EXPERIMENT:
As per the taguchi quality design concept L9 orthogonal
array table was arbitrarily chosen to study optimization
process.
1. Three control factors were chosen each at 3 levels
A- Pulse on time (μs)
B- Duty factor = (pulse on time/(pulse on time + pulse of
time))
C- Pulse peak current (A)
2. Three response parameters were measured
(I) Metal removal rate i.e. MRR (g/min)
(II) Electrode wear rate i.e. EWR (%)
(III)Surface roughness i.e. SR (μm)
Table 3. Machining parameters & their levels
Fig. 3. Grey-based taguchi method procedure
In this paper, the cutting of Tungsten Carbide ceramic using
electro-discharge machining (EDM) with a graphite electrode
by using Taguchi methodology has been reported by
Radzi et al. The Taguchi method is used to formulate the
experimental layout, to analyse the effect of each parameter
on the machining characteristics, and to predict the optimal
choice for each EDM parameter such as peak current, voltage,
pulse duration and interval time. It is found that these
parameters have a significant influence on machining characteristic
such as metal removal rate (MRR), electrode wear
rate (EWR) and surface roughness (SR). The analysis of the
Taguchi method reveals that, in general the peak current
significantly affects the EWR and SR, while, the pulse duration
mainly affects the MRR.
Symbol Parameter Unit Level
1
Level
2
Level
3
A Pulse on μs 5 100 200
time
B Duty factor - 0.2 0.4 0.6
C
Pulse peak
current
3.3 EXPERIMENTAL RESULTS:
A 1 5 7
The experimental results obtained in EDM are given below:
Table 3. Experimental results of process
A B C MRR EWR RA
1 1 1 0.0024 29.896 3.01
1 2 2 0.0058 5.253 2.78
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International Journal of Advanced Technology & Engineering Research (IJATER)
1 3 3 0.0097 4.897 3.45
2 1 2 0.0066 2.345 2.95
2 2 3 0.0087 0.765 2.98
2 3 1 0.0029 28.906 2.5
3 1 3 0.59 0.234 2.12
3 2 1 0.0031 28.865 2.56
3 3 2 0.0037 0.789 2.01
V. REFERANCES
IV. CONCLUSION
1. It can be seen from the graph 1 for MRR to b maximum
factor A, B has to be at level 2 & factor c has to
be at level 3.
2. Pulse peak current is the most critical factor affecting
MRR& duty factor is the least significant parameter.
3. For minimum EWR factor A, C has to be at level 3 &
factor B has to be at level 1.
4. Pulse peak current is the most critical factor affecting
EWR& duty factor is the least significant parameter.
5. For minimum surface roughness factor A, B has to be
at level 3 & factor C has to be at level 2.
6. Pulse on time is the most critical factor affecting surface
roughness & duty factor is the least significant parameter.
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Biographies
1 MANOJ MALIK (MAIN AUTHOR) B.Tech. and
M.Tech. from Maharishi Dayanand University, Rohtak. His
research areas include Manufacturing and Automation field.
manojkumarmalik1984@gmail.com
2 RAKESH KUMAR YADAV, Assistant Professor, Al-
Falah School of Engineering & Technology, Faridabad
rkymech@gmail.com
3 NITESH KUMAR, Assistant Professor, Rawal Institute of
Engineering & Technology, Faridabad
nitesh.bitspilani@gmail.com
4 HARICHAND, Assistant Professor, Rawal Institute of
Engineering & Technology, Faridabad
harichand88@gmail.com
5 DEEPAK SHARMA, Assistant Professor, Rawal Institute
of Engineering & Technology, Faridabad
6 MANOJ, Lecturer, Rawal Institute of Engineering & Technology,
Faridabad.
mrdudeja@gmail.com
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