Experimental investigations, empirical modeling and multi objective optimization of performance characteristics for ECDD with pressurized feeding method Tarlochan Singh, Ranjeet Singh Rathore, Akshay Dvivedi ⇑ Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee, Roorkee 247667, India article info Article history: Received 10 May 2018 Received in revised form 26 August 2019 Accepted 30 August 2019 Available online 6 September 2019 Keywords: ECDD Empirical modelling Performance characteristics Optimization abstract Electrochemical discharge drilling (ECDD) is a hybrid micromachining process that can be used to drill micro holes on all kind of materials, irrespective of their mechanical and electrical properties. In ECDD, the continual penetration of tool electrode having electrochemical discharge (ECD) energy along the work material generates the holes. The relative movements between tool electrode and work material controls the energy penetration rate, and subsequently effects the performance characteristics. Therefore, the effect of process parameters associated with feeding motion and ECD energy are important to investigate simultaneously with respect to the performance characteristics. In the current study, a Buckingham’s dimensional method was used to determine the relation between input process parameters (that includes simultaneous interaction of ECD energy based parameters and feeding motion based parame- ters) and performance characteristics. The material removal rate (MRR) and hole overcut (HOC) were con- sidered as the performance characteristics. MRR and HOC symbolize the productivity and accuracy of the process, respectively. During predictive modeling, the constant terms and coefficients were estimated from the non-linear experimental data. The outcomes manifested by the predictive models are in good agreement with the experimental results. The underlying process mechanism for ECDD with the pressur- ized feeding system has been explored by considering the simulation results as an evidences. Microscopic images of machined holes and discharge characteristics were used to develop the fundamental back- ground of ECDD process mechanism with pressurized feeding method. Additionally, genetic algorithm (GA) was used to perform the multi objective optimization of ECDD process. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction Electrochemical discharge machining (ECDM) is an emerging non-conventional hybrid micro machining process [1]. It is com- posed of two non-conventional machining processes, i.e. electric discharge machining (EDM) process and electrochemical machin- ing (ECM) process [1]. The basic configuration of ECDM process is same as the electrochemical cell circuit (ECC) (Fig. 1a). It consists of two electrodes (where, tool electrode act as a cathode and an auxiliary electrode act as an anode), DC power supply and elec- trolyte. As the DC voltage is supplied across both the electrodes, electrolysis takes place in the electrolyte. The evolution of hydro- gen and oxygen bubbles starts from the tool electrode and auxil- iary electrode, respectively [2]. Further, the coalescence of hydrogen bubbles takes place, and develops an insulated gas film over the tool electrode (Fig. 1b). The insulated gas film restricts the flow of current across the ECC, and thereby it develops high electric field across the gas film [2]. Due to high electric field inten- sity, a breakdown of gas film takes place, and initiates spark dis- charging. In general, the spark discharging initiated from the sharp edges of tool electrode (Fig. 1c). Subsequently, it moves over the entire face of tool electrode [2]. The energy liberated by these spark discharges removes the material from work surface by melt- ing and vaporization. Apart from it, chemical etching also con- tributes to remove the material from work surface [2]. The electrochemical discharge (ECD) energy has been utilized to machine various micro features (such as micro channels, micro pillars and micro holes) using different variants of ECDM process [3–5]. The electrochemical discharge drilling (ECDD) is a process variant of ECDM that is used to machine micro holes [6]. In ECDD, the successive penetration of ECD energy along the longitudinal axis of tool electrode produces micro holes [6]. The relative motion between the tool electrode and work material controls penetration https://doi.org/10.1016/j.measurement.2019.107017 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: akshaydvivedi@gmail.com (A. Dvivedi). Measurement 149 (2020) 107017 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement