Influence of drinking water and graphite powder concentration on

Influence of drinking water and graphite powder concentration on
electrical discharge machining of Ti-6Al-4V alloy
Bhiksha Gugulothu a,⇑
, G. Krishna Mohana Rao b
, D. Hanumantha Rao c
a
Department of Mechanical Engineering, Malla Reddy Engineering College (Autonomous), Maisammaguda Secunderabad, Hyderabad, Telangana 500100, India
b
Department of Mechanical Engineering, Jawaharlal Nehru Technological University, Kukatpally, Hyderabad, Telangana 500028, India
c
Department of Mechanical Engineering, Matrusri Engineering College, Saidabad, Hyderabad, Telangana 500059, India
a r t i c l e i n f o
Article history:
Received 6 September 2019
Received in revised form 18 September
2019
Accepted 5 November 2019
Available online xxxx
Keywords:
EDM
Taguchi method
Graphite powder
Material removal rate
Surface roughness
Recast layer thickness
a b s t r a c t
In the present investigation, the influence of drinking water as dielectric fluid and graphite powder con-
centration on electric discharge machining of Ti-6Al-4V alloy is studied. Taguchi parameter design
approach was used to get an optimal parametric setting of EDM process parameters namely, discharge
current, pulse on time, pulse off time and graphite powder concentration that give up optimal process
performance characteristics such as material removal rate, surface roughness and recast layer thickness.
Also individual effect of process Parameters on performance characteristics was studied. Experiments
were conducted on experimental setup with modified dielectric fluid circulating system. To identify
the significance of parameters on measured response, the analysis of variance (ANOVA) has been done.
Further empirical models were developed by performing nonlinear regression analysis to predict the pro-
cess performance characteristics. Confirmation tests were conducted at their respective optimum para-
metric settings to verify the predicted optimal values of performance characteristics.
Ó 2019 Elsevier Ltd. All rights reserved.
Selection and Peer-review under responsibility of the scientific committee of the First International Con-
ference on Recent Advances in Materials and Manufacturing 2019.
1. Introduction
Ti-6Al-4V shows better mechanical properties even at elevated
temperatures. Despite such tremendous property, its applications
are quite limited to military, aircraft, space craft and medical fields.
The factor limiting its application is high cost and manufacturing
intricacies. Ti-6Al-4V is a material which is difficult-to-machine
due to its poor electrical and thermal conductivity. It chemically
reacts with almost all cutting tool materials. Low cutting speeds,
high feed rates, huge quantity of cutting fluids, sharp tools and
rigid set up are essential for the conventional machining of Ti-
6Al-4V and makes it uneconomical and inefficient [1–3]. EDM
can be employed to overcome the problem faced in conventional
machining of Ti-6Al-4V [4]. Die-sinking EDM is also used to man-
ufacture the components used for aerospace, automobile, tools
and machine tools. EDM is applied for making cavities and minia-
ture holes. With the help of die-sinking EDM, it is possible to make
intricate shaped dies with very less machining time. It can machine
durable materials like Carbide, Steel, Stellites etc., with consider-
ably good surface finish. EDM can be employed for removing bro-
ken taps, drills, studs, reamers, pins. Fragile materials are
machined without any damage by EDM [5]. Tariq Jilani et al. Stud-
ied the different dielectric fluids and two different tool materials. It
has been concluded that best machining was obtained by tap water
[6]. Chen S. L. et al. made a comparative analysis of discharge
machining ofTi-6Al-4V with Kerosene and distilled water as dielec-
tric fluids. Distilled water as a dielectric fluid showed good perfor-
mance compared to Kerosene for MRR and RWR [7]. Lin et al.
optimized machining parameters in magnetic force assisted EDM
based on Taguchi method and found higher MRR, lower RWR and
smaller SR as compared to standard EDM. Significant machining
and optimum combination levels of these parameters have been
determined [8]. Hascalik et al. studied the comparative perfor-
mance of Copper, Graphite and Aluminum electrodes. Increased
surface cracks, MRR, SR and TWR observed with Copper for all pro-
cess parameters. Higher MRR with Graphite and lower SR in Alu-
minum were found [9]. Azad et al. experimentally verified that
voltage and current had influence on optimization of single quality
characteristics and no influence on multiple quality characteristics
[10]. Kung et al. analyzed machinability of Cobalt bonded Tungsten
Carbide (94WC-6CO) with Aluminum powder mixed EDM. It has
https://doi.org/10.1016/j.matpr.2019.11.035
2214-7853/Ó 2019 Elsevier Ltd. All rights reserved.
Selection and Peer-review under responsibility of the scientific committee of the First International Conference on Recent Advances in Materials and Manufacturing 2019.
⇑ Corresponding author.
E-mail address: bhikshamg@gmail.com (B. Gugulothu).
Materials Today: Proceedings xxx (xxxx) xxx
Contents lists available at ScienceDirect
Materials Today: Proceedings
journal homepage: www.elsevier.com/locate/matpr
Please cite this article as: B. Gugulothu, G. Krishna Mohana Rao and D. Hanumantha Rao, Influence of drinking water and graphite powder concentration
on electrical discharge machining of Ti-6Al-4V alloy, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.11.035

been concluded that using Aluminum powder mixed with dielec-
tric distribute the discharge energy gets to increase the machining
efficiency [11].
Kibria et al distinguished the influence of distinct dielectrics like
Kerosene, de-ionized water, B4C powder + Kerosene and B4C pow-
der + de-ionized water. MRR and TWR were observed to be more
and RLT was less with de-ionized water compared with Kerosene.
In case of B4C powder mixed dielectric, material removal rate
increases by de-ionized water, but TWR reduced with Kerosene
[12]. EmreUnses et al observed improvement by adding Graphite
powder into kerosene on EDM of Ti-6Al-4V [13]. Ekmekci et al Per-
formed comparative study on the surface integrity of discharge
machined plastic mold Steel while using Kerosene and de-ionized
water as dielectric fluids. Graphite and Copper as electrodes. For-
mation of white layer was observed on the machined surface in
case of all the dielectric fluids [14]. Bozdana et al. studied rapid
drilling of holes on Ti-6Al-4V by EDM. Brass and Copper tubular
electrodes were used with de-ionized water as dielectric and neg-
ative polarity. It has been observed that MRR increased and TWR
decreased with Brass electrode than Copper electrode [15]. Jahan
et al developed model and investigated the effect of Nano-
powders like Graphite powder (Gr), Aluminum (Al) and Alumina
(Al2O3) separately mixed with Kerosene in micro-EDM of Tungsten
Carbide. Particle size, concentration, density, electrical and thermal
conductivity of powder were found to be the most significant fac-
tors affecting the performance [16].
2. Experimental setups, procedure and equipment:
The die sink EDM (Make: Formatics, Bangalore, India) with
power supply unit and controller PSR-20 (Make: Electronica, Pune,
India) was used for conducting the experiments. The details of the
experimental set up and the closed view of working tank are
shown in Fig. 1.
The experimental set up was modified for conducting the
experiments in the case of powder mixed dielectric fluid. The sche-
matic diagram of experimental set up for PMEDM is shown in
Fig. 1. In this modified experimental set up, powder is mixed into
the dielectric fluid in a separate tank. For conducting experiments,
the work material Ti-6Al-4V. The workpiece of 160 mm length,
60 mm breadth and 6 mm thickness is selected. The Copper elec-
trode of 12 mm diameter is employed for the experiments. The
workpiece material employed in this study is Ti-6Al-4V. Copper
is used as an electrode. Drinking water, are used as dielectric fluids.
The hardness of the material is measured at different points and
average hardness value was found to be 32–34 HRC. The chemical
composition of the Ti-6Al-4V alloy is shown in Table 1. The
mechanical and physical properties of Ti-6Al-4V alloy are
presented in Table 2. Owing to higher thermal conductivity low
electrical resistivity and high melting point, the graphite powder
(particle size 20 to 30 lm) is chosen to add into the dielectric fluid.
The graphite powder morphology can be observed under SEM and
is shown in Fig. 2.
The preliminary experiment result shows that lower MRR is
observed when straight polarity was used. Hence, this study is
focusing on increasing the MRR of the work piece. Using reverse
polarity [17–19]. When the discharge current was kept above
10A, it was observed that the MRR was significant, and when more
than 20A current was selected, it resulted in higher MRR necessi-
tating the selection of values. The range selected for the pulse-on
time and pulse-off time is based on the pilot experiments and
the literature [20]. The pilot experiments were carried out with
the addition of graphite powder from 1 to 20 g/L into the dielectric
fluid. The working range of process parameters in this study is pre-
sented in Table 3.
Three trials of each experiment were conducted to average of
these values to minimize the pure experimental error. Machining
time has been chosen for conducting each experiment is 30 min,
which is sufficient to produce tool shape on work material during
EDM machining of Ti-6Al-4V alloy. The experimental layout for the
present investigation is presented in Table 4.
3. Results and discussion
It is possible to sort out each process parameter on response at
different levels since the experiments are designed in orthogonal
nature.
3.1. Influence of process parameters on MRR
The mean of three trails runs of MRR, SR, and RLT are presented
in the Table 4.
The effect of process parameters on the MRR are presented in
Fig. 3. With the increase in discharge current from 10A to 20A, sig-
nificant increase in MRR is noticed from the response graphs. Dis-
Fig. 1. Modified Experimental setup.
2 B. Gugulothu et al. / Materials Today: Proceedings xxx (xxxx) xxx

charge energy in inter electrode gap is directly influenced by the
discharge current. MRR increases at higher discharge current con-
ditions as a result of high current density that is rapidly over heat-
ing the work piece that caused because of increase in spark energy
[20]. With an enhancement in discharge current, a stronger spark
with high thermal energy is produced and a major portion of heat
is transferred to the electrodes. Further as current increases, dis-
charge strikes the surface of work piece intensively which creates
an impact force on the molten material in the molten puddle and
this results into ejection of more material out of the crater [21].
The trend in variation of MRR with enhancement in discharge cur-
rent is similar with the findings of the pulse on time and is the 2nd
significant factor as far as improvement and importance are con-
cerned. It is clear from Fig. 3 that, as the pulse on time increases
from 25 ms to 65 ms, MRR increases to a smaller extent due to
increase in energy supplied per cycle [22]. Since discharge energy
is not present during pulse off time material removal from work
piece will not take place. With the increase in Ton from 24 ms to
36 ms, MRR increases initially and then decreases. Debris that is
not flushed due to short time available will not allow effective
sparking at low pulse off time and results in unstable machining
process. Debris flushing takes place effectively with the increase
in pulse off time and paves way for effective sparking and stable
machining. Due to this, with pulse off time of 36 ms, MRR enhances
initially and then reduces as quantum of energy supplied to the
process decreases.
MRR decreases initially and increases marginally later with the
increase in Graphite powder combination from 4.5 g/l to 9 g/l.
Excess powder accumulation in the gap reduces the discharge tran-
sitivity and results in MRR reduction Fig. 3 shows that input
parameters like pulse on time, pulse off time, discharge current,
and Graphite powder concentration impact the MRR mean values.
Maximum MRR can be achieved when Ton is at 65 ms (level 3), Toff is
at 36 ms (level 2), discharge current is at 20A (level 3) and powder
combination is at 4.5 g/lt (level 1). Table 5 presents the input
parameters importance on MRR through ANOVA of the data and.
Equation (2) gives the regression equation of MRR. For MRR values
prediction, the R2
and R2
adj are in the variability acceptable range and
the values found are (98.9%) and (95.1%) respectively. MRR is pre-
dicted between the operating ranges of EDM process parameters
by using the regression model.
MRR ¼ 3:76 À 0:892A þ 0:0516B þ 0:280C À 0:511D
þ 0:03052A2
À 0:001239B2
À 0:00526C2
þ 0:0400D2
þ 0:00791AB þ 0:00494AC À 0:01929AD ð2Þ
3.2. Influence of EDM parameters on Ra
The mean values of surface roughness for individual parameters
effect values are given in Table 6. Response curve for the individual
effect of discharge current, pulse on time, pulse off time and Gra-
phite powder concentration on the average values of Ra is shown
in Fig. 4. It is observed from the Fig. 4 that improvement in surface
roughness value is noticed by increase in discharge current. It is
due to the reason that the increase in discharge current enhanced
spark power resulting in the creation of wide and higher cavity
which results in enhanced surface roughness. With the increase
of Graphite powder combination increase from 4.5 g/litre to 9 g/
litre, surface roughness initially decreases and then increases fur-
ther with the increase of powder concentration. Dielectric fluid
insulation strength decreases with the addition of electrical energy
and Graphite powders in dielectric fluid results in gap widening
between electrodes that stabilizes the discharge condition. Lower
surface roughness, shallow craters are produced due to the
reduced electrical density by the widened and enlarged discharge
channel. More heat dissipation from electrode gap through dielec-
tric fluid takes place because of increase in dielectric fluid thermal
Table 1
Chemical Composition of Ti-6Al-4V.
Element C Al V N O Fe H Ti
% Max. 0.08 5.5–6.5 3.5–4.5 0.05 0.13 0.25 0.01 Balance
Table 2
Mechanical and physical Properties of Ti-6Al-4V.
Property Quantity
Hardness (HRC) 32–34
Melting point (°C) 1649
Density (g/cm3
) 4.5
Ultimate tensile strength (MPa) 897–1000
Thermal conductivity (W/m°K) 7.2
Specific heat (J/kg°K) 560
Mean coefficient of thermal expansion 100 °C/°C 08.6 Â 10À6
Volume electrical resistivity (ohm-cm) 170
Elastic Modulus (GPa) 114
Fig. 2. Morphology of graphite powder.
B. Gugulothu et al. / Materials Today: Proceedings xxx (xxxx) xxx 3

conductivity due to powder addition and also the thermal conduc-
tivity available in the work surface decreases [23]. With the
Graphite powder combination increase from 4.5 to 9.0 g/lt, surface
roughness is decreased and further Graphite powder combination
increases from 9 to 13.5 g/lt increases Ra value marginally. Surface
roughness is not significantly affected by the Graphite powder con-
centration from 9 g/l to 13.5 g/l. Table 6 and Fig. 4.
Fig. 4 indicates that minimum work surface roughness can be
obtained when Ton is at 25 ms (level 1), Toff is at 24 ms (level 1), dis-
charge current is at 10A at level 1 and powder concentration is at
9 g/litre at level 2. Table 6 shows input parameters influence on Ra
from ANOVA of the data which is given. From Table 6 it is noticed
that surface roughness is most significantly affected by the
Table 3
Working range of the process Parameters and their levels.
Parameters Units Levels
Discharge current (A) Amps 10 15 20
Pulse on time (B) ms 25 45 65
Pulse off time (C) ms 24 36 48
Graphite powder concentration (D) g/l 4.5 9 13.5
Table 4
Average values of MRR, Ra, and Recast Layer Thickness (RLT).
Ex.
No
A (Discharge Current)
Amps
B (Pulse-On
Time) ms
C (Pulse-Off
Time) ms
D (Graphite Powder
Concentration) g/l
*Avg MRR
(mm3/min)
*Avg Ra
(mm)
*Avg Recast Layer Thickness)
(RLT) (mm)
1 10 25 24 4.5 2.5 2.14 8.04
2 10 25 36 9 2.212 2.126 8.9
3 10 25 48 13.5 2.277 3.641 10.109
4 10 45 24 9 3.057 2.001 8.25
5 10 45 36 13.5 3.681 4.211 8.9054
6 10 45 48 4.5 2.410 4.67 11.253
7 10 65 24 13.5 3.983 3.650 8.4
8 10 65 36 4.5 4.063 4.288 10.379
9 10 65 48 9 1.949 5.27 11.867
10 15 25 24 4.5 3.944 2.308 8.7
11 15 25 36 9 3.327 2.787 9.03
12 15 25 48 13.5 2.217 3.502 9.78
13 15 45 24 9 3.557 2.703 8.6945
14 15 45 36 13.5 4.276 3.657 11.19
15 15 45 48 4.5 4.089 4.33 11.44
16 15 65 24 13.5 5.111 4.25 10.295
17 15 65 36 4.5 6.788 4.495 11.804
18 15 65 48 9 3.223 5.56 11.515
19 20 25 24 4.5 5.029 3.505 9.88
20 20 25 36 9 4.147 3.221 9.5774
21 20 25 48 13.5 3.401 3.654 11
22 20 45 24 9 6.721 4.27 10.9
23 20 45 36 13.5 7.746 4.01 13.24
24 20 45 48 4.5 8.55 4.589 10.536
25 20 65 24 13.5 7.606 5.46 13.449
26 20 65 36 4.5 9.414 5.533 12.615
27 20 65 48 9 8.059 6.41 10.876
*Mean of three values
Fig. 3. EDM parameters on S/N Ratio of MRR.

discharge current whereas other powder concentration doesn’t
have that much effect which is because of the interaction
effect between the parameters. Ra values are predicted by develop-
ing the empirical model using nonlinear regression analysis.
Equation (3) gives the regression equation of SR. The regression
equation of Ra is presented is given in Eq. (3). The R2
and R2
adj
values are found to be 98.5% and 93.6% respectively. The R2
and R2
adj is in the accepted range of values in predicting Ra
value.
SR ¼ 0:91 À 0:084A À 0:0079B þ 0:0531C À 0:105D
þ 0:01215A2 þ 0:000405B2 þ 0:001256C2
þ 0:00877D2 þ 0:00143AB À 0:00607AC À 0:00336AD ð3Þ
3.3. Effect of process parameters on recast layer thickness (RLT)
EDM generated heat affected surface has upper layer called as
recast layer, phase transformative zone and conversional zone in
order given. SEM photo graphs are taken at the cutting machined
zone at the edge of the machined surface to measure RLT for all
the samples machined. Table 4 shows the RLT average values mea-
sured from SEM.
Fig. 5 and Table 7 indicates the parameters effect on the
response. With the increase in discharge current, significant
increase in recast layer thickness is noticed which can be due to
more discharge energy generation causing unstable concentrated
discharge resulting in dielectric flushing efficiency decrease in
the gap. Also, more heat energy leads to increased molten metal
Table 5
Analysis of Variance (ANOVA) for MRR.
Source DF Seq SS Adj SS Adj MS F -Ratio P value Percentage of Contribution (%C)
A (Discharge Current 2 276.095 276.095 138.048 147.91 0.000 56.02
B (Pulse-On-Time 2 89.435 89.435 44.718 47.91 0.000 18.14
C (Pulse-Off-Time) 2 26.554 26.554 13.277 14.23 0.005 5.39
D (Graphite Powder Concentration) 2 28.505 28.505 14.252 15.27 0.004 4.77
A * B 4 27.961 27.961 6.990 7.49 0. 016 5.67
A * C 4 13.107 13.107 3.277 3.51 0. 083 2.65
A * D 4 25.558 25.558 6.390 6.85 0.020 5.18
Residual Error 6 5.600 5.600 0.933
Total 26 492.816 100
S = 0.9661 R2
= 98.9% R2
(adj) = 95.1%
Table 6
ANOVA for SR (Ra).
Source DF Seq SS Adj SS Adj MS F P Percentage of contribution (%)
A (Discharge Current 2 27.223 27.2228 13.6114 28.57 0.001 14.10
B (Pulse- On-Time 2 92.903 92.9033 46.457 97.49 0.000 48.13
C (Pulse-Off-Time) 2 42.737 42.7369 21.3685 44.85 0.000 22.13
A * B 4 0.446 0.4459 0.1115 0.23 0. 909 0.23
A * C 4 14.629 14.6290 3.6572 7.68 0. 015 7.57
A * D 4 7.152 7.1518 1.7879 3.75 0.0073 3.70
Residual Error 6 2.859 2.8588 0.4765
Total 26 193.031 100
S = 0.6903 R-Sq = 98.5% R-Sq(adj) = 93.6%
Fig. 4. Influence of EDM parameters on signal to noise ratio of Ra.

formation which decreases flushing condition that makes more re-
solidified material resulting in the increase of white layer
thickness.
As the pulse on time increases from 25 ms to 65 ms, the RLT also
increases almost linearly. This is due to the fact that at longer pulse
on time, the material removed in vaporized form remains in same
state for longer duration of time and effectively flushed away.
SEM values are observed from Table 4 RLT decreases with
increase in powder combination from 4.5 g/lt to 9 g/lt and
increases with further enhancement in powder combination from
9 to 13.5 g/lt. RLT reduces due to decrease in amount of heat avail-
able at work piece, this accounts by lower single spark discharge
energy and increased spark frequency with the addition of Gra-
phite powder in dielectric fluid. Recast layer thickness increases
with increase in concentration of powder in dielectric up to 9 g/lt
to 13.5 g/lt. It can be observed that RLT value is minimum when
Graphite powder combination is 9 g/lit i.e. Level 2, Ton at 25 ms
(level 1), discharge current at 10 A (level 1), Toff at 24 ms (level
1). Mathematical model of RLT (response variable) is developed
by nonlinear regression analysis which is given in Eq. (4). The val-
ues R2
and R2
adj are in acceptable range which is 91.70% and 85.62%
respectively.
However, R2
adj (85.62%) is low due to the inclusion of in-
significant parameters in the model. Further, we can predict RLT
using by Eq. (4).
RLT ¼ 1:02 þ 0:138 A þ 0:0414B þ 0:445C À 0:945D
þ 0:00729A2
À 0:000361B2
À 0:00243C2
þ 0:0324D2
þ 0:00240 AB À 0:01438 AC þ 0:02561 AD ð4Þ
4. Confirmation experiments for influence of drinking water
and Graphite powder concentration on electrical discharge
machining of Ti-6Al-4V alloy
Material removal rate, surface roughness and recast layer thick-
ness predicted values were confirmed. Table 8 represents the data
of confirmation experiments, compared with respective prediction
values and the deviations of prediction results.
5. Conclusions
Based on the experimental results in the present work, the fol-
lowing conclusions are drawn:
1. In the case of drinking water with Graphite powder addition,
the maximum MRR is 10.567 mm3
/min. The optimum condition
of MRR is 10.567 mm3
/min at A3B3C2D1 (discharge current (I) at
20A, pulse on time (Ton) at 65 ms, pulse off time (Toff) at 36 ms
and Graphite powder combination at 4.5 g/l).
Fig. 5. Influence of EDM parameters on signal to noise ratio of RLT.
Table 7
Analysis of Variance (ANOVA) for RLT.
Source DF Seq SS Adj SS Adj MS F P Percentage of Contribution (%)
A (Discharge Current) 2 10.1679 10.1679 5.08396 97.48 0.000 24.84
B (Pulse-On-Time) 2 9.8915 9.8915 4.94573 94.83 0.000 24.16
C (Pulse-Off-Time) 2 7.0165 7.0165 3.50826 67.27 0.003 17.14
A * B 4 0.6256 0.6256 0.15639 3.00 0. 0111 1.52
A * C 4 7.2974 7.2974 1.82435 34.98 0. 000 17.83
A * D 4 3.8222 3.8222 0.95554 18.32 0.002 9.33
Residual error 6 0.3129 0.3129 0.05215
Total 26 40.9267 100

2. The minimum surface roughness is during EDM of Ti-6Al-4V is
observed to be 2.231 mm at A1B1C1D2 (discharge current (I) at
10A, pulse on time (Ton) at 25 ms, pulse off time (Toff) at 24 ms
and Graphite powder concentration at 9.0 g/l).
3. The minimum recast layer thickness is 8.432 mm during EDM of
Ti-6Al-4V is observed at A1B1C1D2 (discharge current (I) at 10A,
pulse on time (Ton) at 25 ms, pulse off time (Toff) at 24 ms and
Graphite powder concentration at 9.0 (g/l)
4. When powder concentration is 9 g/lt SR value attains maxi-
mum, below that concentration SR increases and then decreases
with increase in concentrated powder to 13.5 g/lt.
5. RLT value decreases with Powder combination from 4.5 to 9 g/lt
and further enhances with improvement in powder concentra-
tion from 9 g/lt to 13.5 g/lt.
6. Based on the results, ANOVA analysis, discharge current is
found to be most significant parameter affecting MRR, SR, and
RLT. However, powder concentration is having less significance
7. Optimal parametric settings were found for all performance
characteristics. Corresponding optimum response values are
calculated and also confirmation experimentation was man-
aged at particular optimum parametric location to check pre-
dicted optimal value. The matching % error values were
estimated and the values are in the range of 7.78% to 9.57%.
8. Different Graphite powder concentration in drinking water is
used as the input process parameter, the optimal level of Gra-
phite powder found to be as 4.5 g/l is sufficient to maximize
the MRR and 9.0 g/lt to reduce the SR and RLT.
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Table 8
Prediction and experimental results of MRR, SR, and RLT at various optimum conditions.
SNO Optimum parameters Optimum
response
Optimum
condition
Predicted
value
Experiential
value
% of
Error
A (Discharge
Current)
B (Pulse On-
Time)
C (Pulse Off-
Time)
D (Graphite Powder
Concentration)
1 20 65 48 4.5 MRR (mm3
/
min)
A3B3C2D1 9.64352 10.567 9.57
2 10 25 24 9 SR (mm) A1B1C1D2 1.2545 2.231 7.78
3 10 25 24 9 RLT (mm) A1B1C1D2 7.78446 8.432 8.31
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