Abstract
Electro-chemical discharge machining (ECDM) of electrically non-conductive high-strength–high-temperature-resistant ceramics such
as aluminium oxide (Al2O3) by trepanning method (i.e. orbital motion of tool) has shown the possibility of drilling large size holes by
comparatively smaller electrodes efficiently and economically. However, at greater machined depth, the conventional electrode
configurations and machining parameters show that machining performance gradually deteriorates with increase in tool depth and finally
cause micro cracks on the machined surface due to thermal shocks at high voltage. To reduce this problem and to enhance the machining
performance during trepanning operation of Al2O3, a spring fed cylindrical abrasive electrode of 1.5mm diameter has been used under
the effect of the three most influential parameters, namely, pulsed DC supply voltage, duty factor and electrolyte conductivity, each at
five different levels to assess the volume of material removed, machined depth and diameteral overcut. The results obtained from this
study revealed that pulsed DC has reduced the tendency of cracking at high supply voltage compared to smooth DC and the machining
ability of the abrasive electrode was better than copper electrode as it would enhance the cutting ability due to the presence of abrasive
grains during machining. In addition to this, trepanning provides the scope for drilling bigger holes.
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