1 An Investigation of Tube and Rod Electrode Wear in Micro EDM Drilling D. T. Pham, A. Ivanov, S. Bigot, K. Popov and S. Dimov IMRC, Manufacturing Engineering Centre, Cardiff University Abstract This paper studies the influence of various factors contributing to micro electrode wear during EDM drilling with micro rod and micro tube electrodes. In the paper a simple method for calculating volumetric wear ratios is proposed based only on geometrical information obtained from the process. The objective of the research is to investigate the wear behaviour of electrodes and the suitability of electrode wear compensation methods. Electrode shape deformation and random variation of the volumetric wear are studied as the main factors affecting the applicability of wear compensation methods and as an indicator of the accuracy achievable with the micro EDM process. Keywords: Micro EDM, Micro machining, EDM accuracy, Electrode wear, Micro holes and cavities 1. Introduction The EDM process is essentially based on the thermo-electric energy created between a workpiece and an electrode submerged in a dielectric fluid. When workpiece and electrode are separated by a specific small gap, the so-called ‘spark gap’, a pulsed discharge from the electrode removes material from the workpiece through melting and evaporation. In conventional Electro Discharge Machining (EDM) (die sinking), wear on the tool electrode is a well known phenomenon [1]. Errors caused by electrode wear in this case are often negligible when considering the feature sizes and tolerances required. Typical die sinking methods based on the use of one or more electrodes for roughing followed by an electrode for finishing are not applicable for machining micro features because combining micro features and macro features on one electrode will introduce different wear characteristics. The surface of the sparking area will change as the electrode progresses into the workpiece, which will invoke different sparking conditions during the process and will reduce the final quality of the part. In addition, the micro features on the electrode will suffer