Investigation on hybrid electrochemical discharge drilling process using passivating electrolyte

Hybrid electrochemical discharge machining is a machining method materialized by distinct techniques which combines effects of material removal specific to electrochemical machining and electrical discharge machining. The research presented in this paper aimed to design, build and test an in-house equipment for hybrid electrochemical discharge machining and to study the electrochemical discharge drilling using a rotating tool and a passivating electrolyte. Theoretical conditions for obtaining small diameter holes by electrochemical discharge drilling were investigated. One considered that an aqueous solution of soluble sodium silicate would behave as a passivating electrolyte. In order to break and remove the passivating film, the rotating cylindrical tool could be periodically pressed on workpiece surface, the equipment being designed considering the above mentioned work motions. The equipment was built and the results of preliminary experimental tests proved the possibilities of obtaining small diameter holes, by using cylindrical tools of 0.5-1.0 mm diameter, with periodical increasing of the distance between the frontal surface of the tool electrode and the workpiece surface. The shape of current and voltage pulses were highlighted by use of data acquisition board. (C) 2016 The Authors. Published by Elsevier B.V.