Optimisation and Experimental Investigation of Material Removal Rate and Tool Wear Rate of Micro Electro Discharge Machining (MEDM) of Hastelloy C276

With rapid development in micromachining, high aspect ratio (AR > 10) micro-holes are essentially required in applications such as spinneret holes, biomedical needles, fuel injectors, cooling channels, etc. Machining such high aspect ratio micro holes on superalloys are challenging for micromachining processes. A high aspect ratio micro hole can be machined via. Micro Electrical Discharge Machining (MEDM) process with optimum levels of operating parameters. Work reported in this paper is aimed to investigate the effect of machining parameters of MEDM to produc micro-holes in Hastelloy C276. Extensive experimentations based on Taguchi Designs of Experiments (DOE) were conducted to identify the most influential processing parameters while machining micro holes of more than 10 aspect ratios. The experimental results are discussed which quantify an individual and combined effect of different operating parameters on the overall performance of MEDM like material removal rate (MRR) and tool wear rate (TWR). It is found that capacitance and spindle rotation speed are the most important parameters controlling the stability of the process. A direct relation of TWR has been found with discharge energy (capacitance and voltage). At optimum process parameter conditions, the aspect ratio (depth/diameter) of 12.5 is achieved while machining holes with 400 mu m diameter.