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
capacity. Very low wire speed would lead to the situation similar to the stationary tool resulting in overheating
and finally breaking of the wire. Too high wire speed was also not desirable because it would be uneconomical.
Hence, wire was driven by stepper motor at a constant speed of 650mm/min. An aqueous solution of NaOH with
different electrolyte solution at 20ºC was used. NaOH has higher specific conductance, reactions take place at
higher rates, so a larger amount of gases were evolved. Hence, higher MRR was achieved. Therefore, all the
experiments reported in this paper were carried out using NaOH solution as electrolyte. Each experiment was
tested for about 15 to 20 min, during which voltage and current were recorded on a voltmeter and ammeter,
respectively. The minimum linear feed rate to the workpiece which could be achieved using the present setup
was 0.008mm/s.
The thermo mechanical phenomenon has also been identified as the main mechanism responsible for material
removal and surface roughness in TW-ECSM. Voltage, pulse on-time and electrolyte concentration were
considered as controllable variables and their effects on material removal rate and surface roughness were the
responses of the process. For evaluation of MRR, the loss in weight of the machined specimen was measured on
a weighing digital microbalance (accuracy 10 µg, CAS India Private Limited). After machining, the workpiece
was washed, dried to evaporate any water remaining on the surface and reweighed using a weighing digital micro
balance. The difference between the initial weight and the final weight was given the amount of material
removed. The surface roughness characteristic was measured in terms of center line average values (R a ) using a
surface texture meter by Taylor Hobson, UK. In this work, material removal rate in millimeter per minute and
surface roughness in micrometer have been taken.
4. RESULTS AND DISCUSSION
The effects of major process variables such as supply voltage, pulse on-time and electrolyte concentration on
material removal rate and surface roughness have been analyzed for obtaining the machining characteristics of
borosilicate glass when using TW-ECSM process.
4.1. Influence of voltage on MRR and R
a
The effect of applied voltage on MRR in TW-ECSM process, for keeping other parameters constant is shown in
Fig. 3. Here, it is observed that MRR increases with increase in various supplied voltage such as 45V, 50V and
55V. There is no spark below 35V and wire randomly breaks above 55V. An increase in the applied voltage
implies higher discharge energy per spark hence more heat generated resulting in enhanced MRR. However, with
the increase in voltage the electrolysis process is accelerated hence, the rate of generation of hydrogen gas
bubbles is increased and consequently the rate of generation of discharge energy increases. At high machining
voltage, micro-cracks form on the work surface has been obtained.
3.4
3.2
0.25mm Dia.
3.0
MRR (mm 3 /min)
2.8
2.6
2.4
2.2
2.0
40 45 50 55 60
Voltage (V)
Fig. 3 Effect of applied voltage on the MRR for the 0.25mm brass wire diameter
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