11. Investigations into Micro-Hole Drilling on SS-304 by Sequential Electro-Micro Machining

This paper focuses on the improvement of performances in sequential electro-micro-machining (SEMM) which consists of micro-EDM and micro-ECM processes during drilling micro-holes on SS-304 stainless steel sheet. In the first phase of experimentation, through micro-holes drilling on SS-304 material was done by applying micro-EDM process. As EDM being a thermal process, shaping of an object takes place rapidly due to high intensity spark discharges, but these spark discharges also create heat-affected zone consisting of recast layer, craters, cracks, and so on. These defects are then ameliorated by micro-ECM process performed sequentially after micro-EDM. This paper investigates the effects of machining time on the post electro-discharge machined holes for the various machining responses, such as radial overcut, circularity and hole taper. The experiments revealed that with the increase in machining time, there is an improvement in hole circularity as well as hole taper angle, but undesirable radial overcut also escalates with the passage of time.