INVESTIGATION AND PARAMETRIC OPTIMIZATION OF ELECTROLYTIC JET DRILLING PROCESS WITH MOVING TOOL

Abstract

This thesis reports about the experimental investigations on precision machining of nickel-chromium based alloy Incoloy 330 by electrolytic jet drilling process, one of the variant of electrochemical machining (ECM) process. In EJD, the acid electrolyte is passing under pressure through glass tube nozzle, coming jet act as cathode and work piece as anode. Material removal takes place when stream of electrolyte strikes work piece causing removal of metal ions from work piece. In the present work, as trend towards miniaturization continues micro hole drilling techniques is more significant where small and micro sized 'hole to be drilled with high aspect ratio as well as in multiple numbers in extremely hard and brittle materials Electrolytic jet drilling process (EJD) which meets this requisite existing experimental setup for EJD has been modified machining of Incoloy 330, by designing and fabricating a tooling system and machining chamber. The experimental investigations involved studying the effects of three key input parameters namely voltage, electrolyte concentration, and feed rate, on the measure of EJD process performance namely material removal rate (MRR), radial overcut (ROC) and velocity of dissolution (VOD).Experimental plan involved three-phase experiments: pilot, main, and confirmation experiments. Pilot experiments were conducted to study the effect of stand- off distance and electrolyte temperature on EJD process in order to fix their value by varying one parameter at a time. Based upon the pilot experiment results, 1 mm standoff distance and 36 °C electrolyte temperature is fixed for the main experiments, main experiment were designed using Box-Behnken approach of response surface methodology (RSM) in which DC voltage, feed rate and electrolyte concentration were varied in the ranges of 180 — 220 volts,0 .12-.20 mm/min and 15-25 % electrolyte concentration respectively. Development of regression models and their statistical analysis including ANOVA, for the three responses namely MRR, ROC and VOD have been done with the help of design-expert 7.1.6 software. study of the main effects and interaction effects of the variable process parameters on the responses has been done. Optimum combination of the process parameters has been found using the desirability analysis