In situ drilling and milling of thin sheet using microelectrical discharge machining

Abstract

The present study investigates fabrication of microrod using block electrical discharge grinding process and performs in situ drilling and milling of thin sheets using the fabricated rods by the microelectrical discharge machining process. The microrods are fabricated at a wide range of discharge energy (DE) by varying voltage and capacitance, and their effect on machining time (MT), material removal rate, average diameter and standard deviation in diameter (SDD) are evaluated. To get the benefit of both higher efficiency as well as dimensional accuracy, a technique of variable energy setting is coined, wherein higher DE is applied initially to increase efficiency followed by lower DE to improve dimensional accuracy and precision. The fabricated microrods are then used as tools for in situ microelectrical discharge drilling (µED-drilling) and microelectrical discharge milling (µED-milling) on brass and titanium sheet. In µED-drilling, MT and tool wear (TW) of brass is lower as compared to titanium, whereas overcut of brass is higher than titanium. ‘To and fro’ technique is used to compensate the TW in µED-milling and to achieve dimensional accuracy. The technique is successful in achieving fairly straight microslot in brass with SDD of 17 µm as compared to titanium with SDD of 113.50 µm.