MRR and TWR Analysis of EDM Process Using MWCNT

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 184-192 © IAEME
184
EXPERIMENT INVESTIGATION OF EDM PARAMETER MRR AND TWR
WITH MULTI WALL CARBON NANO TUBES
Prof. Yashesh Darji1
, Prof. Pankaj L Koradiya2
, Prof. Jigesh R.Shah3
1, 2
(C U Shah College of Engineering & Technology, Mechanical Department,
Wadhwancity surendranagar, Gujarat, India)
3
(C U Shah College of Engineering & Technology, Automobile Department,
Wadhwancity surendranagar, Gujarat, India)
ABSTRACT
Electric discharge machining is non conventional machining process used for machining of
hard materials which cannot be machined by conventional machining process. Electric discharge
machining is an electro sparking method of metal working involving an electric erosion effect. A
pulse discharge occurs in a small gap between the work piece and the electrode and removes the
unwanted material from the parent metal through melting and vaporizing.
Powder-mixed electrical discharge machining is one of the latest techniques for improving
material removal rate and also decreased tool wear ratio, How ever its utilization in the
manufacturing industry is very low because many fundamental issues of this new development such
as machining mechanism cost effectiveness of powder and powder concentration in the working
fluid together with safety and environmental impact among other are not well understood.
This work investigation the machining characteristics of EN-31 with aluminum as tool
electrode during EDM process, The multi wall carbon nano tube is mixed with dielectric fluids in
EDM process to analyze the MRR, TWR. Regression model were developed to predict the out put
parameter in EDM process. In the development of predictive models, machining parameter of peak
current, pulse on time and pulse off time were considered as model variables. The collection of
experimental data adopted full factorial method. Analysis of variance (ANOVA) to determine the
significant parameter affecting the out put parameter. Later EN-31 steel was analyzed and the
parameters are optimized using design expert software, regression equations are compared with and
without MWCNT using EDM process. The average 19% of MRR was improved where TWR was
8.51% decreased with respect to input parameter.
Keywords: Electrical discharge machining (EDM), Carbon nanotubes (CNT), Material removal rate,
tool wear rate, full factorial method, Regression Analysis.
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 5, Issue 7, July (2014), pp. 184-192
© IAEME: www.iaeme.com/IJMET.asp
Journal Impact Factor (2014): 7.5377 (Calculated by GISI)
www.jifactor.com
IJMET
© I A E M E

185
INTRODUCTION
Electrical discharge machining (EDM) is one of the most successful and widely accepted
processes for production of complicated shapes and tiny apertures with high accuracy. This method
is commonly used for profile truing of metal bond diamond wheel, micro nozzle fabrication, drilling
of composites and manufacturing of moulds, and dies in hardened steels. These hard and brittle
materials fabricated by conventional machining operation cause excessive tool wear and expense.
The mechanical properties of tool steels have been studied extensively for many years. During EDM,
the tool and the work piece are separated by a small gap, and submerged in dielectric fluid. The
discharge energy produces very high temperatures on the surface of the work piece at the point of the
spark. The specimen is subject to a temperature rise of up to 40,000 K causing a minute part of the
work piece to be melted and vaporized. The top surface of work piece subsequently resolidifies and
cools at very high rate. EDM technology is increasingly being used in tool, die and mould making
industries, for machining of heat treated tool steels and advanced materials (super alloys, ceramics
and metal matrix composites) requiring high precision, complex shapes and high surface finish.
Traditional machining technique is often based on the material removal & tool wear rate. carbon
nanotubes (CNTs). Ozlem and Cengiz (2008) pro-posed roughness values obtained from the
experiments that have been modeled by using the genetic expression programming (GEP) method
and a mathematical relationship has been suggested between the GEP model and SR and parameters
affecting it. Moreover, EDM has been used by applying copper, copper–tungsten (W–Cu) and
graphite electrodes to the same material with experimental parameters designed in accordance with
the Taguchi method. Yan-Cherng et al. (2009) developed the force assisted standard EDM machine.
The effects of magnetic force on EDM machining characteristics were explored. Moreover, this work
adopted an L18 orthogonal array based on Taguchi method to conduct a series of experiments and
statistically evaluated the experimental data by analysis of variance (ANOVA). Ko-Ta et al. (2007)
proposed a methodology for modeling and analysis of the rapidly resolidified layer of spheroidal
graphite (SG) cast iron in the EDM process using the response surface methodology. The results of
ANOVA indicate that the proposed mathematical model obtained can adequately describes the
performance within the limits of the factors being studied.
ABOUT CARBON NANO TUBE
CNTs are related to graphite. The molecular structure of graphite resembles stacked, one-
atom-thick sheets of chicken wire, a planar network of interconnected hexagonal rings of carbon
atoms. In conventional graphite, the sheets of carbon are stacked on top of one another, allowing
them to easily slide over each other. That is why graphite is not hard, but it feels greasy and can be
used as a lubricant. When grapheme sheets are rolled into a cylinder and their edges joined, they
form MWCNT (Table 3). Only the tangents of the graphitic planes come into contact with each
other, and hence their properties are more like those of a molecule as mentioned in the above passage
clearly. Furthermore, the high-frequency carbon-carbon bond vibrations provide an intrinsic thermal
conductivity higher than even diamond. The TEM images of multi wall carbon nano tubes are shown
in Figure 1 were received from Cheap tubes Inc., USA. CNT nano fluids, is of special interests to
researchers because of the novel properties of CNTs -extraordinary strength, unique electrical
properties and efficient conductors of heat. CNTs are fullerene-related structures that consist of
either a grapheme cylinder or a number of concentric cylinders (Wen and Ding, 2004). Choi et al.
(2001) measured the effective thermal conductivity of MWCNTs dispersed in synthetic (poly-α-
olefin) oil and reported the enhancement up to a 150% in conductivity at approximately 1 vol%
CNT, which is by far the highest thermal conductivity enhancement ever achieved in a liquid
(Lockwood and Zhang, 2005). Solid lubricants are useful for conditions when conventional liquid

186
lubricants are inadequate such as high temperature and extreme contact pressures. Their lubricating
properties are attributed to a layered structure on the molecular level with weak bonding between
layers. Such layers are able to slide relative to each other with minimal applied force, thus giving
them their low friction properties. CNT is having high strength to weight ratio used in aero space
industry. Young’s modulus of CNT is over 1 TPa versus 70 GPa for aluminium, steel 200 Gpa and
700 GPa for C-fibre. The strength to weight ratio is 500 times greater than aluminium. Maximum
strain will be 10% much higher than any material. Thermal conductivity of 3,000 W/mK in the axial
direction is with small values in the radial direction. Conductivity of CNTs is 109 A/cm2 and copper
is 106 A/cm2. CNT’s having very high current carrying capacity, excellent field emitter and high
aspect ratio. Model Hommel Tester TR500 SR tester is a multi-application measuring instrument for
component surface quality evaluation. It is capable of checking the work piece SR on plane, cylinder,
groove and bearing raceway.
In this paper, CNT mixed dielectric fluids are used in the EDM process to analyze the EDM
parameter like MRR & TWR of EN-31 tool steel material. Till now, no work has been carried out by
using CNT mixed dielectric machining. CNT based nano fluid is used to improve the Material
removal rate & tool wear rate The collection of experimental data adopted Full Factorial using Table
5 coded level of three machining parameters. ANOVA and regression model and to determine the
significant parameter affecting the Material removal rate and tool wear rate Later the En-31 tool steel
was analyzed and the parameters are optimized using design expert software and regression equation
are compared with and without multiwall carbon nanotubes used in EDM process.
Figure 1: Micro structure of CNT
DIELECTRIC CYCLING SYSTEM
Due to the larger size of the in built container in the EDM machine, it is not appropriate to
mix the powder in the bigger container. So we need to design the container to avoid the mixing of
powder particles in the bigger container of the machine. More over, filter of machine might clog due
to presence of powder particles and debris when using existing circulation system of machine itself.
So a new container with capacity of 6.0 liters was developed in the workshop for the dielectric fluid.
It was placed in the existing container of EDM machine and experiments were performed in this
container. Special types of two stirrers are fixing with proto type new tank for proper circulation of
powder mixed dielectric fluid into discharge gap between tool electrode and work piece material,
Mixed 0.5 g/l CNT in dielectric fluid, Fig 2 show the mechanism of proto type tank and Fig 3 shown
the proto type tank is using in EDM machine.

187
Figure 2: double stirrers for powder circulation
Figure 3: EDM with proto type tank
Evaluation of MRR
The material MRR is expressed as the ratio of the difference of weight of the work piece
before and after machining to the machining time and density of the material.
MRR =
ௐ௝௕ିௐ௝௔
௧ ƍ
Whereas Wjb = Weight of work piece before machining.
Wja = Weight of work piece after machining.
t = Machining time
ƍ = Density of EN-31 steel material
Evaluation of tool wear rate
TWR is expressed as the ratio of the difference of weight of the tool before and after
machining to the machining time. That can be explaining this equation.
TWR =
ௐ௧௕ିௐ௧௔
௧ ƍ

188
Whereas Wtb = Weight of the tool before machining.
Wta = Weight of the tool after machining.
t = Machining time.
Conduct of Experiments
The work piece material as EN-31 was particulate using Aluminum tool with 15 mm
diameter and work piece dimension were 30 x 30 x 30 mm square cube. JOEMARS - Made: Z 50
JM-322 EDM machine was used for conducting experiment. Commercial kerosene and also
MWCNT mixed kerosene used as dielectric fluid. In this experiment three EDM parameters such
as pulse on time, pulse off time and peak current are varied at three levels of each. For a three factor
are tackled with a total number of 27 experiments performed on die sinking EDM. Three responses
such as material removal rate and surface roughness and tool were ratios are measure as output
parameters. The material removal rate and tool were ratio are calculated by using weight machine
having the capacity of 200 gram and accuracy is 0.01 gram.
RESULTS AND DISCUSSION
Table 3: Comparison of regression model with experiment measurements
Sr
no
With CNTs MRR Without CNTs MRR With CNTs TWR Without CNTs MRR
Experiment
data
Regression
data
Experiment
data
Regression
data
Experiment
data
Regression
data
Experiment
data
Regression
data
1 20.528 19.120 17.363 16.025 1.967 1.755 2.129 1.896
2 58.977 52.600 49.407 43.799 6.451 6.371 6.962 6.913
3 45.026 43.809 37.885 36.630 5.03 5.684 5.438 6.173
4 23.925 21.362 19.867 18.111 3.294 3.059 3.591 3.332
5 34.093 32.799 27.996 27.387 4.507 3.705 4.882 4.017
6 22.506 24.637 19.127 20.653 2.647 2.750 2.871 2.984
7 24.413 24.008 20.649 20.218 3.271 3.018 3.529 3.277
8 16.064 14.725 13.503 12.441 0.956 1.411 1.045 1.526
9 21.696 22.887 18.197 19.175 2.654 2.366 2.886 2.559
10 26.480 27.283 21.968 22.759 2.723 2.709 2.931 2.929
11 46.854 42.688 38.611 35.587 4.867 5.032 5.262 5.455
12 38.897 37.172 32.261 30.960 3.531 4.037 3.826 4.367
13 13.539 10.329 11.535 8.8571 1.165 1.068 1.258 1.157
14 30.198 33.920 25.566 28.430 4.661 4.357 5.092 4.735
15 40.150 41.567 33.414 34.544 3.907 4.380 4.189 4.737
16 35.386 38.3161 29.789 32.014 5.264 4.700 5.727 5.105
17 18.822 15.846 15.974 13.484 1.953 2.063 2.124 2.244
18 26.237 25.758 22.254 21.696 2.11 3.402 2.257 3.702
19 19.110 18.492 16.044 15.591 2.724 2.023 2.956 2.189
20 27.983 30.153 23.292 25.280 2.855 3.745 3.126 4.072
21 21.232 20.241 17.853 17.068 1.898 2.407 2.056 2.614
22 29.156 32.776 24.63 27.375 3.001 3.694 3.257 3.997
23 45.055 47.084 37.49 39.171 5.645 5.375 6.148 5.825
24 52.084 48.205 43.038 40.214 6.39 6.027 6.985 6.543
25 25.101 29.525 21.108 24.845 4.489 4.013 4.881 4.365
26 32.947 38.293 27.636 32.003 4.86 4.689 5.273 5.085
27 25.541 28.404 21.675 23.802 4.396 3.361 4.779 3.647

189
Fig 4 Graph of without CNT for MRR Fig 5 Graph of with CNT for MRR
Effect of carbon nano tube on MRR
The mean MRR for CNT + kerosene was 58.977 mm3
/min and that of pure kerosene was
49.407 mm3
/min at 28A and pulse on time 65 micro sec. and pulse off time 30 micro sec. The
experimental results show that the CNT powder concentration of 0.5 g/l .high concentrations of CNT
powder in the gap often made the EDM process unstable. ”c.mai. Hong et. [25] It is observed from
the graph the MRR is increase with respect to increase in Peak current and pulse on time. This
increase of MRR with concentration could be attributed in kerosene. Spark gap is filled with additive
particles which reduces the insulating strength of the dielectric fluid and increased spark gap between
the tool and work piece. It was also possible that the best combination of particle striking and powder
density take place at this concentration.
Fig 6 Graph of without CNT for TWR Fig 7 Graph of with CNT for TWR
Effect of carbon nano tube on TWR
The means TWR for CNT + kerosene was 0.956mm3
/min and that of pure kerosene was
1.045mm3
/min at 17A and pulse on time 45 micro sec. and pulse of time 45 micro sec. The
experimental results show that the CNT powder concentration of 0.5 g/l. It is clear from the graph
that the peak current and pulse on time and CNT concentration are the main influencing factor in the
tool wear rate. Pulse off time and polarity are less influencing factor for tool wear rate .when CNT
mixed with kerosene than created lubricant layer around tool and work piece this mixer keep cool
the electrode and that’s why the tool wear rate is decrease.
Design-Expert® Software
MRR
X1 = A: peakcurrent
X2 = B: pulse on time
Actual Factor
C: pulse off time = 30
17
21
28
45
55
65
16
23.25
30.5
37.75
45
MRR
A: peak currentB: pulse on time
MRR
X1 = A: peak current
Actual Factor
17
21
28
45
55
65
9
16.25
23.5
30.75
38
MRR
twr cnt
X1 = A: peakcurrent
Actual Factor
17
21
28
45
55
65
1.4
2.6
3.8
5
6.2
twrcnt
twr cnt
X1 = A: peakcurrent
Actual Factor
17
21
28
45
55
65
0.7
1.9
3.1
4.3
5.5
twrcnt

190
CONCLUSION
Process parameters do not have same effect for every response. Significant parameters and its
percentage contribution changes as per the behavior of the parameter with objective response
Finding the result of MRR the most significant factor was found to be peak current followed
by pulse on time and the least significant was pulse off time. The MRR increased linearly
with the increase in current. For pulse on time the MRR first increased with linearly with
increase in pulse off time, MRR decreased insignificantly.
In the case of Tool wear rate the most important factor is peak current then pulse on time and
after that pulse off time.
Effect of carbon nano tube on MRR for CNT + kerosene was 58.977 mm3
/min and that of
pure kerosene was 49.407 mm3
/min from experimental result with carbon nano tube the
average 19% of MRR increased with respect to input parameter.
Effect of carbon nano tube on TWR for CNT + kerosene was 0.956mm3
/min and that of pure
kerosene was 1.045mm3
/min from experimental result with carbon nano tube the average
8.51% of TWR decreased with respect to input parameter.
Table 1: Major properties of EN-31 & Chemical Composition and grades: GCr15, 102Cr6,
L1/L3/52100, SUJ2
Material Thermal conductivity
(W/mk)
Density (g/cc) Electrical
resistivity
Specific heat
capacity
(J/g-‘c)
EN-31 46.6 7.81 o.oooo218 0.475
C si Mn Cr p V Fe
1.07 0.32 0.58 0.03 0.04 1.12 Balance
Table 2: specification of MWCNT
Aspect Ratio ˜1000
Specific Surface Area 350 m2
/g
Purity –wt% >95%
Metallic Impurity <5%
Average outer Diameter 20-40nm
Average inner diameter 5 nm
Number of Walls 5-15
Length 50µm

191
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MRR and TWR Analysis of EDM Process Using MWCNT

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