Performance of a Copper Electroplated Plastic Electrical Discharge Machining Electrode Compared to a Copper Electrode 1 Saroj Kumar Padhi, 2 S.S. Mahappatra and 3 Harish Chandra Das 1 Department of Mechanical Engineering, Institute of Technical Education and Research, Siksha ‘O’ Anusandhan University, Bhubaneswar, India. [email protected]2 Department of Mechanical Engineering, National Institute of Technology, Rourkela, India. 3 Department of Mechanical Engineering, Institute of Technical Education and Research, Siksha ‘O’ Anusandhan University, Bhubaneswar, India. Abstract Electro discharge machining is an important unconventional machining process being widely used in modern industrial applications and precession works. Electrode is the most vital element of the electrical discharge machining (EDM) system, working like a cutting tool, highly responsible for the qualitative and quantitative responses. The present findings are made on an electrode of acrylonitrile butadine sterane (ABS) plastic, fabricated through fused deposition modeling (FDM), one of the additive manufacturing (AM) process. A copper layer of about 1000 microns is deposited on the FDM ABS plastic part by thick electroplating, which made it practicable in EDM applications. Performances of the EDM operation with the copper coated plastic and a copper electrode are studied while machining D2 steel. As a result the copper coated plastic electrode performed well without failure and less tool wear. Key Words:Additive manufacturing, rapid tool, thick copper electroplating, FDM, EDM electrode, response Surface method. International Journal of Pure and Applied Mathematics Volume 114 No. 7 2017, 459-469 ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version) url: http://www.ijpam.eu Special Issue ijpam.eu 459
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Performance of a Copper Electroplated Plastic
Electrical Discharge Machining Electrode Compared
to a Copper Electrode 1Saroj Kumar Padhi,
2S.S. Mahappatra and
3Harish Chandra Das
1Department of Mechanical Engineering,
Institute of Technical Education and Research,
Siksha ‘O’ Anusandhan University, Bhubaneswar, India.
* RQM =Reduced Quadratic Model, PSS = Partial sum of squares, SS = Sum of Squares
df = degrees of freedom, MS = Mean Square value, p-value = Prob > F
Table 5: Box-Behnken design table with experimental data of Cu tool Copper tool Operating voltage 40 V Machining time 6 minutes
Std. run Factor-I A:Ip amp
Factor -II B: Ton
μs
Factor-III
C:Tau %
Response-I
R1 SR
Response-II
R2 TWR
Response-III
R3 MRR
1 2 50 10 75 3.890 0.037202381 1.75
2 4 50 10 75 5.423 0.074404762 3.40
3 2 150 10 75 3.620 0.055803571 1.88
4 4 150 10 75 4.757 0.093005952 2.98
5 2 100 9 70 3.107 0.037202381 1.99
6 4 100 9 70 4.984 0.074404762 2.88
7 2 100 11 80 2.850 0.055803571 2.05
8 4 100 11 80 5.158 0.093005952 3.63
9 3 50 9 70 4.150 0.055803571 2.45
10 3 150 9 70 4.516 0.074404762 2.10
11 3 50 11 80 4.564 0.055803571 2.75
12 3 150 11 80 4.057 0.074404762 2.25
13 3 100 10 75 3.875 0.055803571 2.52
14 3 100 10 75 3.985 0.074404762 2.32
15 3 100 10 75 3.483 0.055803571 2.65
Table 6: The Analysis of variance table for Response Surface-copper tool MRR data
C. Analysis of Factors and Responses Analysis of variance (ANOVA) is an imperative method to analyze the
performances of definite response factors by decomposing the inconsistency in
the response variable between dissimilar factors. In Table 3 and 5, the results of
RT and copper tool are tabulated respectively. Responses influenced by
different input parameters are analysed critically at 0.05 significant level,
eleminating the insignificant parametrs from the ANOVA table for that
* RQM, PSS Type-III MRR C T
Source *SS *
df
*MS FValue *p-value
Model 4.09 8 0.51 29 < 0.0001 Significant
A-Discharge Current 3.41 1 3.41 193.08 < 0.0001
B-Pulse-on-time 0.16 1 0.16 9.21 0.0162
C-Duty Factor 0.2 1 0.2 11.25 0.01
AB 0.076 1 0.076 4.29 0.0722
AC 0.12 1 0.12 6.75 0.0317
BC 5.63E-03 1 5.63E-03 0.32 5.88E-02
A2 0.067 1 0.067 3.67 0.0875
B2 0.065 1 0.065 3.69 0.0909
-Residual 0.14 8 0.018
Lack-of- Fit 0.066 4 0.016 0.87 0.5522 Non- significant
Pure-Error 0.075 4 0.019
Cor Total 4.23 1
6
* RQM =Reduced Quadratic Model, PSS = Partial sum of squares, *SS = Sum of Squares
*df = degrees of freedom, *MS = Mean Square value, *p-value = Prob > F
International Journal of Pure and Applied Mathematics Special Issue
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response. MRR, SR and TWR represents the output responses of the input
parameters i.e. discharge-current A = I, pulse on time B = Ton and duty-factor C
= τ, their square terms 1 A2, B
2, C
2 and interactive terms as A*B, A*C, B*C.
Similarly, the ANOVA for all responses (MRR, SR and TWR) are analyzed and
studied for the most significant and insignificant combinations of parameters for
the various output responses. The Rapid tool and copper tool ANOVA table for
MRR are given in Table 4 and 6 respectively after eliminating the insignificant
parameters. Similarly, the analyses for all the responses are analyzed and
ultimate equations are framed using the coded factors. After analyzing the most
influencing factors on the responses of MRR, it is observed that factors A, B, C
and the square terms A2, B
2 and interactive terms A*B are significant
parameters. For the responses of TWR from the ANOVA it is seen that A, B
and C influence more along with, A2, C
2 and BC, which are significant. AB, AC
and B2 are the insignificant parameters. The ANOVA for SR it is found that A,
B and square term A2 are the important process parameters and process
parameter C is the insignificant one. For the rapid tool, the coefficient of
determination (R2) and the adjusted R2 values are as follows: 94.79 and 91.67
% for the MRR, 98.93 and 97.56% for the TWR and 98.28 and 96.08 % for the
SR. It is observed that for all the responses lack-of-fit is insignificant.
3D Graphs: Performances of Copper Tool and Rapid Tool (RT)
The RSM Box-Behnken design/analysis graphs: input parameters influencing
output responses. 3D graphs are ploted with three mutually perpendicular axis
X, Y and Z. X and Y represents input factors and Z carries the response. For
each of the three responses SR, TWR and MRR, three input parametric
combinations of A, B and C and two electrodes, nine pairs of graphs are plotted
and analyzed. Due to similarity in the performance plots of both the tool
electrodes, one pair of graph are demonstrated here. The variation in SR (R1)
for the copper tool and rapid tool, with parameters A and B are shown in Figure
5(a, b). The surface quality machined through both the electrodes decreases by
increasing the intensity of current. Though the increased value of C influences a
little, pulse-on-time (B) is more influential in reducing the SR as studied from
the graphs. Analyzing the influences of C and A also of C and B on the
Response-I (SR) there are no remarkable changes on SR graphs with the factors,
i.e. for both the tools performances are similar. The normal-plot of residuals for
the surface responses of MRR is shown in Figure 5(c), describing the data
points scattered from the mean. Closure the data points to the mean holds good
results in the response surface plots. Influences of B and A on R1 is plotted.
Figure 5(a): Copper tool 5(b): Rapid tool 5(c): Normal plots for MRR
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The variations in results of most of all the graphs plotted for the tool types are
nearly same. Experimentally it is observed that TWR for Copper electrode is
slightly more than the rapid tool. The graph indicates that the TWR for both the
electrodes increases proportionately with A and B but it indicates a little
variation from the effects of increased C. It is marked that higher values of A
and C gives higher MRR (R3), but for the two different tools comparatively
there is a little variation. There are no significant variations in graphs for the
two tools, indicating performances, those are nearly same for the factor B and A
along with factor C and B on response-III (MRR). MRR increases by increasing
A and a slight change while increasing B, however, it decreases after the value
of B is set to low. Similarly, it is shown for A and C that the increased value of
A increases MRR but the influence of C is small. (A = Current, B =Ton (Pulse-
on-time), C = Duty factor and R1 is the response I = SR, R2 is the response II =
TWR and R3 is the response III = MRR).
4. Conclusion
It is possible to fabricate an RT electrode of FDM extrudd ABS plastic within a
short period of time. Required thickness and surface conditions can be achived
by electroplating bath solution (additives) and special arrangements. The
performances of both the EDM electrodes on machining D2 steel are executed.
It is revealed that wear of RT electrode is comparably less. MRR for both the
tools are nearly same. In case of the RT (copper electroplated plastic tool), the
deposited metal is in purest form of copper, carries more current to discharge,
enhances MRR comparing to a solid copper tool. It is seen that the RT
machined surface roughness is more due to the RT electrode surface quality,
which can be enhanced to use it for finishing operations.
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