OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
time of 0.20ms to 0.40ms. Because higher energy discharge takes place during sparking, results more amount of
heat energy penetrating into the workpiece which causes larger crater on the machined surface. Hence, R a
increases with increase in pulse on-time. The graph clearly shows that the lowest value of R a =11.2µm and the
highest value of R a =14.8µm.
15.0
14.5
0.25mm wire Dia
14.0
13.5
R a
(µm)
13.0
12.5
12.0
11.5
11.0
4.3. Influence of electrolyte concentration on MRR and R
a
MRR increases with an increase in electrolyte concentration up to 20% i.e. 200g/l and then starts decreasing.
This is due to the fact that the specific conductance of NaOH solution increases upto 20 percent concentration,
beyond which its start decreasing as shown in Fig. 7. An increase in specific conductance means increased
electrolyte conductivity and consequently more current. An increase in electrolytic current would mean the
accelerated electrolysis process. It would result in a greater rate of evolution of hydrogen gas bubbles at the
cathode. The increased rate of formation of gas bubbles at the cathode implies an enhanced rate of sparking and
hence higher MRR
2.34
0.20 0.25 0.30 0.35 0.40
T ON
(ms)
Fig. 6 Effect of pulse on-time on the R a for the 0.25mm brass wire diameter
2.33
2.32
0.25mm Dia.
2.31
MRR (mm 3 /min)
2.30
2.29
2.28
2.27
2.26
2.25
120 140 160 180 200 220 240 260 280
Electrolyte concentration (g/l)
Fig. 7 Effect of electrolyte concentration on the MRR for the 0.25mm brass wire diameter
The effect of electrolyte concentration on surface roughness in TW-ECSM process, for keeping other parameters
constant is shown in Fig. 8. The electrolyte concentration considered for the experiments were 150g/l, 200g/l and
250g/l. The reason for this variation is that the specific conductance of NaOH solution increases upto 200g/l
electrolyte concentration, beyond which it starts decreasing. An increase in specific conductance means an
increased electrolyte conductivity, which results more circuit current. At higher values of circuit current means
more heat energy penetrates into the workpiece and consequently larger value of depth of crater. But beyond at a
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