A strategy to improve performance in electrochemical discharge machining using periodic bi-directional tool rotation

Increasing machining depth has imposed challenges to machine high aspect ratio features in electrochemical discharge
machining (ECDM) of hard and brittle materials like borosilicate glass. As depth of machining (DOM) progresses, the
machining is slowed due to insufficient availability of electrolyte at the tool tip. The stagnated electrolyte at the entrance of
the hole causes increased radial overcut (ROC), heat-affected zone (HAZ), and taper (TP) and also reduced material removal
rate (MRR), DOM, and circularity (CR). To overcome these challenges, the present study implemented a novel strategy
using periodic bi-directional tool rotation (PBTR) with tungsten carbide helical drill. Initially, a flow simulation with KOH
electrolyte has been conducted using COMSOL multi-physics platform to understand effect of the tool rotation on machining
characteristics for both unidirectional tool rotation (UTR) and PBTR. It is found from the simulation that the PBTR shows
better electrolyte supply to the tool tip as compared to UTR. Experiments are conducted with experimental plan based on
L16 array. Experimental results disclosed that PBTR has resulted an improvement in MRR, DOM, and circularity and a
decrease in HAZ, ROC, and TP of the machined hole. Parametric optimization is carried out using teaching learning-based
optimization (TLBO) algorithm to evaluate the optimum process parameters. Optimum values are confirmed with by the
experimental results