Report final

1
CHAPTER-1
Introduction
Electrical discharge machining (EDM) is one of the must extensively used non-
conventional, thermo-electric metal removal process which encodes material from the
work place by a series of discrete spark between a work and a tool electrode immersed in
a liquid dielectric medium. Electrical energy is used directly to cut the material in final
shape. Melting and vaporization takes place by theses electrical discharges. The minute a
mounts of the work material is then ejected and flushed away by the dielectric medium.
The sparks occur at high frequency which continuously and effectively removes the work
prices material by melting and evaporation. To initiate the machine process electrode and
work piece are separated by a small gap known as ‘spark gap’ which results into a pulsed
discharge causing the removal of material. The dielectric acts as a deionizing medium
between two electrodes and its flow helps in vacating the resoliclified debris to assure
optimal conditions for spark generation. In micro-wire EDM operation the work piece
metal is cut with a special metal wire electrode that is programmed to travel along a
definite path. Spark discharges and generated between a small wire electrode and a work
piece to produce complex two dimensional and three-dimensional shapes according to a
NC path. A very thin wire in the range of 0.02 to 0.3 mm in diameter as an electrode is
used in the wire-cut EDM. It machines a work piece with electrical discharge like a bands
haw by moving either the work piece or the wire. The mechanism of metal removal is
same as in connectional EDM. The most prominent feature of a moving wire is that a
complicated cutout can be early machined without using a forming electrode.
The CNC system of wire EDM has the duty to provide the function of geometry
trajectory, sequential control, pulse generator control, wire feed and wire tension control
and machining process control. The wire transport system of a wire EDM guarantees a
smooth wire transport and constant tension of wire.
The machine consists of a work piece contour movement control unit, work piece
mounting table and wire driven part which ensures accurate movement of the wire oat
constant tension. The purpose of WEDM is to achieve better stability and higher
productivity, higher machining rate with accuracy. A large number of variables are
involved in the process; also the nature of the process is stochastic. Hence even a highly

2
skilled operator is unable to perform the optimal performance. Although WEDM
machines available today have some kind of process control, still selection is very tough
to ensure optimal setting.
PRINCIPLE OF WIRE ELECTRICAL DISCHARGE MACHINING
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 an insulated dielectric fluid (water).
Many sparks can be observed at one time. This is because actual discharges can occur
more than one hundred thousand times per second, with discharge sparks lasting in the
range of 1/1,000,000 of a second or less. The volume of metal removed during this short
period of spark discharge depends on the desired cutting speed and the surface finish
required.
The heat of each electrical spark, estimated at around 15,000° to 21,000° Fahrenheit,
erodes away a tiny bit of material that is vaporized and melted from the work piece.
(Some of the wire material is also eroded away) These particles (chips) are flushed away
from the cut with a stream of de-ionized water through the top and bottom flushing
nozzles.
The water also prevents heat build-up in the work piece. Without this cooling, thermal
expansion of the part would affect size and positional accuracy. Keep in mind that it is the
ON and OFF time of the spark that is repeated over and over that removes material, not
just the flow of electric current.

3
1.1 Important features of wire EDM
1. Electrode wear is negligible.
2. Forming electrode to produce shape is not required.
3. Machined surface are very smooth.
4. Dimensional and Geometrical Tolerances are very tight.
5. Straight hole production is possible with higher precision.
6. Relative tolerance between punch and die is much higher and die life is extended.
7. The machine can be operated unattended for long time at high rate.
8. No special skills are required to run the machine.
9. Any electrically conductive material can be machined irrespective of its hardness.
10. This process allows the shaping and machining of complex structure with high
machining accuracy in the order of micron. The surface roughness achievable is
Rz = 0
1.2 Objective
There are a lot of parameters which affect the wire EDM machine performance. It
is very though to derive exact and real mathematical models between machining
performance and machining parameters. The reason is very complex mechanism
involved in the process. The main objective is as follows:-
1. To determine significant parameters affecting the performance of machining.
2. To discuss the cause effect relationship of machining parameters and the
performance in WEDM.
3. Achieving the shortest machining time, satisfying the accuracy and surface
roughness requirements.
4. To establish the mathematical model to relate machining parameters and
machining performance by regression and correlation analysis.
5. To find out important parameters affecting the performance of machining.
6. The optimal machining parameters are obtained under constraint and
requirements.

4
1.3 Process parameters of wire EDM process
Table 1.1
S.No. Parameters Range
1. Frequency 0-200KHz
2. Pulse width 1-
3. Gap% of Voltage 60-100%
4. Gain 0-100
5. Pulse peak currant 40A
6. Output Voltage 60-250V
7. Dwell time 0.205
8. Polarity +/-
9. Hole diameter 0.05-1mm
10. Spindle speed 100-1000 ___
Machine Parameters:
1. Table feed.
2. Pulse on time.
3. Pulse off time.
4. Flushing
Wire Parameters:
1. Material of wire.
2. Diameter of wire.
3. Wire speed.
4. Wire tension.
Phase 1:
 Development of experimental set up providing varying range of input parameters
in WEDM.
 Investigation of the working ranges and the levels of the WEDM process
parameters.

5
Phase 2:
 Investigation of the effects of WEDM process parameters on quality
characteristics viz. cutting rate, surface roughness while machining of h13
diesteel.
 Prediction of optimal sets of WEDM process parameters .
 Prediction of optimal values of quality characteristics.
Fig 1.1
ADVANTAGES AND DISADVANTAGES OF WIRE EDM:
1. Complex shape that would otherwise be difficult to produce with conventional cutting
tools.
2. Extremely hard materials to very close tolerances.
3. Very small work pieces where conventional machining tools may damage the part from
excess cutting tool pressure
4. There is no direct contact between tool and work piece. Therefore delicate sections and
week materials can be machined without any distortion.
DISADVANTAGES:
1. Relatively low rate of material removal.
2. Additional heat time and cost used for creating electrodes for ram/sinker EDM.

6
3. Reproducing shape corners on the work piece is difficult due to electrode wear .
Influence of Process parameters on the Wire EDM process:-
The main goal of WEDM manufacturers and users is to achieve a better stability of the
process and higher productivity. As newer, more exotic materials are developed, and
more complex shapes are presented, conventional machining operations reach their
limitations; hence the increased use of WEDM in manufacturing continues to grow at an
accelerated rate. Wire electrical discharge machining manufacturers and user emphasize
on achievement of higher machining productivity with a desired accuracy and surface
finish. However, due to a large number of variables even a highly skilled operator with a
state-of the art WEDM is rarely able to achieve the optimal performance.
Factors influencing the Wire
Fig:1.2

7
Influence of Wire Positioning:-
It is necessary to hold the wire in a designated position against the object because the wire
repeats complex oscillations due to electrical discharge between wire and the work piece.
It may also be noted that the unsupported length of wire changes with thickness of the job
jeopardizing the wire vibration frequency. The computer controlled positioning system
constantly maintains the gap between the wire and the work piece. Disturbances from the
external and internal sources generate vibrations in the wire, which ultimately influence
the repetitive sparking process in spite of the controlled positioning system. This
deviation of the electrode from its mean position therefore has considerable influence on
the occurrence of the next discharge. It also influences the breakdown voltage of the
discharge and the discharge energy since the gap is changing continuously during the
vibration.
A desirable wire material for WEDM electrode should posses following
properties:
 Adequate tensile strength with high fracture toughness.
 High electrical conductivity [% IACS - International Annealed Copper Standard, a
unit of electrical conductivity for metals and alloys relative to a standard annealed
copper conductor; an IACS value of 100% refers to a conductivity of 5.80 × 107
siemens per meter (58.0 MS/m)].
 Good flushing ability.
 Low melting point and Low energy requirement to melt and vaporize.
.
Flushing Pressure :-
The commonly used flushing methods are immersion flushing, spray or jet flushing.
Figure 1.6, shows the curve of influence of flushing pressure on machining speed and
surface roughness. The cutting performances during roughing cuts have been improved

8
since the removed particles in the machining gap are evacuated more efficiently (the
pressure must be reduced during finishing in order to avoid geometrical part errors). It
can be seen that when flushing pressure is less than certain pressure value, it is impossible
to do any machining . Along with increased flushing pressure the machining speed also
increases, but when it is over 1 kg/cm2 (98066.5Pa), the increased trend slows down
while the surface roughness improves gradually with increased flushing pressure; due to
effective removal of debris. When flushing pressure is less than 0.3kg/cm2.
Fig 1.3
Along with increased flushing pressure the machining speed also increases, but when it is
over 1 kg/cm2 (98066.5Pa), the increased trend slows down while the surface roughness
improves gradually with increased flushing pressure; due to effective removal of debris.
When flushing pressure is less than 0.3kg/cm2 (29420Pa), high temperature is easily
registered along electric discharge area.

9
CHAPTER 2
Literature Review
Effect of process parameters on material removal rate in wire EDM:
The effect of various process parameters of WEDM like pulse on time (Ton),pulse
off time(Toff),gap voltage(SV),peak current (IP) is investigated.The paper reveals there
influence on the MRR of hot die steel(H-13).one variable at a time approach is used .the
experiments were carried out on Electronica Sprint cut WEDM.
Nihat Tosun et.al investigated on the effects and optimization of machining
parameters on the (cutting width) and material removal rate (MRR) in wire EDM
operation .the experiments were conducted under various wire speed ,open circuit voltage
,pulse duration and dielectic flushing pressure .the design of experiment was done using
Taguchi Method.
A mathematical model was developed correlating the various wire EDM
parameters like peak current, duty factor, wire tension and water present by Hewidy et al.
[9].the variation of above parameters were correlated with MRR.
Experimental Methodology:
ELECTRONICA SPRINTCUT WEDM machine was used to perform the experiments.
The effects of the various inputs parameters, pulse on time (Ton), pulse off time (Toff),
servo voltage and input current are studies on MRR and SURFACE ROUGHNESS.
Master Brass wire with 0.25 diameter (900N/mm
2
,tensile strength) was used in the
experiment.The work piece material ,H-13 hot die steel with 125mm×100mm×24mm was
used.During the experiment 5mm×5mm square was cut to obtain a rectangular punch of
5mm×5mm×24mm.
Optimizing the process variables:
The EDM process involves complicated discharge mechanism ,that is why it is
very stochastic in nature.various process variables are correlated with performance
measures to maximize the MRR,whereas to minimize the tool wear rate(TWR) and

10
yielding the desired surface roughness.S/N ratio coupled with the analysis of variance
(ANOVA) technique are used to measure the amount of deviation from the desired
performance measure.The process variables include electrical and non-electrical
parameters both . an objective function under the multi-constraint conditions is
formulated which is based on the mathematical model developed. The optimization
problem is solved by the feasible direction method to obtain the the optimal machining
parameters . Experimental results demonstrate that the machining models are appropriate
and the derived machining parameters satisfy the actual requirements in practice.
A study on machining parameter optimization:
A proper selection of machining parameters is a must for the wire electrical
discharge machining .the selection depends mainly on the operators technology and
experience because the range of parameters is quite diverse .Based on the Taguchi quality
design method and ANOVA,an approach to determine parameter setting is proposed in
the paper.The important factors affecting the machining parameters like MRR,gap
width,surface roughness,sparking frequency,average gap voltage and normal ratio are
determined.Mathematical models are established using regression analysis.Objective
function under the multi constrain condition is formulated based on the mathematical
model developed.
Experimental equipment and design of experiment
1. work piece (anode) : hot h13 diesteel;
2. electrode (cathode) : 00.25 mm brass wire;
3. work piece height : 30 mm;
4. cutting length : 20 mm;
5. open voltage : 95 V;
6. servo reference voltage: 10 V ,and
7. specific resistance of fluid : 1-3 mA

11
Design of experiments:
L9 mixed arrays table was chosen for the experiment.4 controlling factors having
three levels(small,medium and large)were selected as controlling factors:
1. Pulse on time
2. Pulse off time
3. servo volatge
4. Input current
1. Machine Tool:
The experiments were carried out on a wire-cut EDM machine of central
institute of tool designing installed at Advanced Manufacturing Laboratory of
Mechanical Engineering Department, Hyderabad India.
The WEDM machine tool (Figure) has the following specifications:
DESIGN OF EXPERIMENT:
A wire EDM machine in C.I.T.D (Central Institute of Tool Design)
Work material: EN8 carbon steels.
Electrode: Ø0.25 mm brass wire
Work piece height: 30mm
Cutting height: 20mm
Open voltage: 95V
Servo reference voltage: 10 V
Specific resistance of fluid: 1-3mA

12
2. Work piece material:
The H-13hot die steel plate of 200mm x 50mm x 20mm size has been used as a
work piece material for the present experiments. H-13 is special hot-worked chromium
tool-steel with good hardness and toughness properties. It is used for extreme load
conditions such as hot-work forging, extrusion etc. It has varied practical applications
such as manufacturing of punching tools, mandrels, mechanical press forging die, plastic
mould and die-casting dies, aircraft landing gears, helicopter rotor blades and shafts. The
working life and dimensional accuracy of H-13steel dies and tools can be improved with
suitable heat treatment. The chemical composition of this material as obtained by In
House Method(jsapl/sop/02/0) test is given in following table:
Table 2.1
Material
identification
C Si Mn P S Cr Mo Ni V
Die-steel 0.37 0.85 0.43 0.011 0.06 5.18 1.25 0.11 0.89
Specif
ied
values
min 0.32 0.8 .2 - - 4.75 1.1 - 0.8
max
0.45 1.2 0.5 .03 .03 5.5 1.75 0.3 1.2
Result: the elements tested are within limits of the above specifications
3. Measurement of experimental parameters:
The discussions related to the measurement of WEDM experimental parameters
e.g. material removal rate, surface roughnes are presented in the following subsections:
Material removal rate:
For WEDM, cutting rate is a desirable characteristic and it should be as high as
possible to give least machine cycle time leading to increased productivity. In the present
study cutting rate is a measure of job cutting which is digitally displayed on the screen of
the machine and is given quantitatively in mm/min.
Surface roughness:
Roughness is often a good predictor of the performance of a mechanical
component, since irregularities in the surface may form nucleation sites for cracks or
corrosion. Roughness is a measure of the texture of a surface. It is quantified by the

13
vertical deviations of a real surface from its ideal form. If these deviations are large, the
surface is rough; if small, the surface is smooth. Roughness is typically considered to be
the high frequency, short wavelength component of a measured surface.
The parameter mostly used for general surface roughness is Ra. It measures
average roughness by comparing all the peaks and valleys to the mean line, and then
averaging them all over the entire cut-off length. Cut-off length is the length that the
stylus is dragged across the surface; a longer cut-off length will give a more average
value, and a shorter cut-off length might give a less accurate result over a shorter stretch
of surface. In this work the surface roughness was measured by Mitutoyo surftest SJ-201P
(Figure).The surftest is a shop–floor type surface-roughness measuring instrument, which
traces the surface of various machine parts and calculates the surface roughness based on
roughness standards, and displays the results in µm. The work piece is attached to the
detector unit of the SJ-201P which traces the minute irregularities of the work piece
surface. The vertical stylus displacement during the trace is processed and digitally
displayed on the liquid crystal display of the SJ-201P. The surf test has a resolution
varying from .01 µm to 0.4 µm depending on the measurement range.
3. SELECTION OF PROCESS PARAMETERS:
 PULSE ON TIME
 PULSE OFF TIME
 SERVO GAP VOLTAGE
 INPUT CURRENT(PEAK CURRENT)
Pulse On Time:
The pulse on time is referred as Ton and it represents the duration of time in micro
seconds, µs, for which the current is flowing in each cycle .During this time the voltage,
VP, is applied across the electrodes. The Ton setting time range available on the machine
tool is 105-115 which is applied. The equivalent time setting in micro seconds is given
The single pulse discharge energy increases with increasing Ton period, resulting in
higher cutting rate. With higher values of Ton, however, surface roughness tends to be
higher. The higher value of discharge energy may also cause wire breakage.
Ton

14
V Toff
Pulse Off Time:
The pulse off time is referred as Toff and it represents the duration of time in micro
seconds, µs, between the two simultaneous sparks.The voltage is absent during this part
of the cycle. The Toff setting time range available on the machine tool is 45-60 which is
applied in steps of 1 unit. The equivalent time setting in micro seconds is given in With a
lower value of Toff, there are more number of discharges in a given time, resulting in
increase in the sparking efficiency. As a result, the cutting rate also increases. Using very
low values of Toff period, however, may cause wire breakage which in turn reduces the
cutting efficiency. As and when the discharge conditions become unstable, one can
increase the Toff period. This will allow lower pulse duty factor and will reduce the
average gap current.
.
Fig 2.1
Peak Current:
The peak current is represented by IP and it is the maximum value of the current
passing through the electrodes for the given pulse. The IP setting current range available
on the present WEDM machine is 8-12 ampere which is applied in steps of ampere.
Increase in the IP value will increase the pulse discharge energy which in turn can
improve the cutting rate further. For higher value of IP, gap conditions may become

15
unstable with improper combination of Ton, Toff, SV settings. As and when the discharge
conditions become unstable one must reduce the IP value.
Servo Voltage:The spark gap set voltage is a reference voltage for the actual gap between
the work piece and the wire used for cutting. The SV voltage range available on the
present machine is 10-30 volt and is applied in steps of 1volt.
Workpiece after milling
Fig :2.2

16
fig 2.3
Cleaning work after machining using emery

17
Parameters on Nc machine
Fig:2.4

18
CHAPTER 3
Optimization Techniques
Taguchi method
Taguchi’s method is an efficient tool for the design of high quality manufacturing
system.Dr.Genichi Taguchi,a Japanese engineer has developed a method based on
orthogonal arrays (OA).In this method quality is measured by the deviation of a
characteristic from its target value.A loss function is developed from this
deviation.uncontrollable factors which are also known as noise cause such deviation and
result into loss.taguchi method seeks to minimize the noise because the elimination of
noise factor is impractical.this method provides much reduced variance for the
experiment with optimum setting of process control parameters.So taguchi philosophy is
based on integration of design of experiments(DOE) with parametric optimization of
processes to get the desired results.
Fig 3.1

19
CHAPTER- 4
Experimental Details
1. According to the taguchi design method L9 Orthogonal array was
chosen for the optimization of the process.
Fig 4.1
2.Four control factors were chosen at three
Pulse on
Pulse off
Servo Voltage
Input Current

20
Effect of input parameters on surface roughness:
The pulse on time (Ton) is varied from 105 unit to 115 unit in steps of 3 units. The
values of the other parameters are kept changing and their values are given as Toff varied
between 45 to 60 unit; IP between 8 to 12; SV between 20 and 40 volt. The
experimentally observed data for the response characteristics for different values of pulse
on time is given in Table.
Table 4.1
Ton Toff sv Ip Cs(mm/min) Ra(µm)
105 45 20 8 1.5318 3.8
105 48 30 10 1.4049 1.6
105 60 40 12 0.6018 1.2
110 45 30 12 1.7896 3.6
110 48 40 8 1.8293 3.4
110 60 20 10 1.443 2.8
115 45 40 10 1.756 3.2
115 48 20 12 2.096 3.8
115 60 30 8 1.9347 2.8
Table 4.2
Mean1 Mean2 Mean3
Ton 2.2 2.9 3.13
Toff 3.2 2.66 2.4
Sv 3.2 2.46 2.6
Ip 3.46 2.53 2.26
Optimum conditions are:
(Ton)11+(Toff)23+(Sv)32+(Ip)43
Mean surface roughness =2.33=ŋm
Optimim surface roughness
Ŋoptimum=ŋm+∑4
i=1(ŋij-ŋm)
= 2.33+(2.2-2.33)+(2.4-2.33)+(2.46-2.33)+(2.26-2.33)
=2.33

21
From the above table the following graphs are drawn between the Ton against
surface roughness, Toff against surface roughness, servo gap voltage vs surface
roughness and between input current and surface roughness.
Workpiece after cutting
Fig:4.2

22
Profilometer
Fig 4.3
Profilometer is a measuring instrument used to measure a surface's profile, in order to
quantify its roughness. A typical profilometer can measure small vertical features ranging
in height from 10 nanometers to 1 millimeter. There are two types of profilometers
contact and non-contact type profilometers. We used contact type profilometer to fine
surface roughness of hot diesteel material.

23
CHAPTER 5
RESULTS AND DISCUSSIONS
DATA ANALYSIS:
Graph showing pulse on time with surface roughness:
The value of surface roughness though increases with increase in pulse on time
but rather with a little wavy pattern and is shown in Figure
Fig 5.1

25
Fig 5.4
Analysis:
The optimum condition is identified by studying the main effects of each of the
parameters. The main effects indicate the general trends of influence of each parameter.
The knowledge of contribution of individual parameters is a key in deciding the nature of
control to be established on a production process. The analysis of variance (ANOVA) is
the statistical treatment most commonly applied to the results of the experiments in
determining the percent contribution of each parameter against a stated level of
confidence. Study of ANOVA table for a given analysis helps to determine which of the
parameters need control.
Anova(Analysis of variance):
Where y1, y2, y3 are the actual units of charectersitc
n is number of units in given sample
k is Constant depending on the magnitude of the characteristic and the monetary
unit involved
m Target value at which the characteristic should be set

26
Table 5.1
Mean1 Mean2 Mean3 Ss %contribution
Ton 2.2 2.9 3.13 2.94 2.94/12.05=24.3
Toff 3.2 2.66 2.44 2.61 2.61/12.05=21
Sv 3.2 2.46 2.6 2.54 2.54/12.05=21
IP 3.46 2.53 2.26 3.96 3.96/12.05=32
= 12.05
SS=SUM OF THE SQUARES
(SS)TON=3(2.2-2.33)^2+3(2.9-2.33)^2+3(3.13-2.33)^2 = 2.94
(SS)TOFF=3(3.2-2.33)^2+3(2.66-2.33)^2+3(2.4-2.33)^2 = 2.61
(SS)SV=3(3.2-2.33)^2+3(2.46-2.33)^2+3(2.6-2.33)^2 = 2.54
(SS)IP=3(3.46-2.33)^2+3(2.53-2.33)^2+3(2.26-2.33)^2 = 3.96
2. EFFECT OF INPUT PARAMETERS ON MATERIAL REMOVAL RATE
(MRR):
Table 5.2
Ton Toff sv Ip Cs(mm/min) MRR=t*b*CS
105 45 20 8 1.5318 306.36
105 48 30 10 1.4049 280.8
105 60 40 12 0.6018 120.36
110 45 30 12 1.7896 357.92
110 48 40 8 1.8293 365.8
110 60 20 10 1.443 288.6
115 45 40 10 1.756 351.2
115 48 20 12 2.096 403.9
115 60 30 8 1.9347 386.9
MATERIAL REMOAVAL RATE=THICKNESS*BREADTH*CUTTING SPEED
The material should be high so marking higher value for calculating optimum condition
for the MRR.

27
Table 5.3
Mean1 Mean2 Mean3
Ton 235.84 337.44 380.6
Toff 338.52 350.16 265.2
Sv 332.9 341.7 279.14
Ip 352.98 306.89 294.07
Optimum condition for the mrr:
(Ton)13 (Toff)22 (Sv)32 (Ip)41.
GRAPHS SHOWING THE VARIATION BETWEEN INPUT AND PERFORMANCE
MEASURES:

29
Fig 5.8
Analysis:
The optimum condition is identified by studying the main effects of each of the
parameters. The main effects indicate the general trends of influence of each parameter.
The knowledge of contribution of individual parameters is a key in deciding the nature of
control to be established on a production process. The analysis of variance (ANOVA) is
the statistical treatment most commonly applied to the results of the experiments in
determining the percent contribution of each parameter against a stated level of
confidence. Study of ANOVA table for a given analysis helps to determine which of the
parameters need control
Analysis of Variance (ANOVA) of MRR:
Table 5.4
Mean1 Mean2 Mean3 Ss %contributio
n
Ton 235.84 337.4 380.6 33557.02 57
Toff 338 350.16 265.2 12729.52 21.6
Sv 332.9 341.7 279.14 6783.32 11.53
IP 352.98 306.89 294.57 5759.32 9
=58828.29

30
(SS)TON=3(338.52-318)^2+3(350.6-318)^2+3(265.2-318)^2 = 12729.52
(SS) TOFF=3(235.94-318)^2+3(337.43-318)^2+3(380.6-318)^2 = 33557.02
(SS)SV=3(332.9-318)^2+3(341.7-318)^2+3(279.14-318)^2 = 6783.32
(SS)IP=3(352.98-318)^2+3(306.89-318)^2+3(294.07-318)^2 = 5759.032

31
CHAPTER - 6
Conclusions:
Optimization of micro wire EDM process on h13 die-steel was studied in this thesis.
Wire EDM is a complex process having many numbers of factors affecting the
process, but for current study the main factors considered are: pulseontime, pulse
off time,servovoltage and input current
.
The effects of these factors on surface roughness and MRR have been studied.
For optimizing the process variables ANOVA method has been applied
When speed increases then material removal rate decreases at equal rates.
When Pulse off time increases then material removal rate decreases at equal rates.
When pulse on time increases then material removal rate decreases at equal rates
When surface roughness decreases then material removal rate decreases at equal
rates.

32
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