Effects of tool electrode size on surface characteristics in micro-EDM

Micro-electrical discharge machining (micro-EDM) is one of the most effective and economical processing methods for micro-features with good dimensional accuracy and repeatability. During micro-EDM, the energy stored in stray capacitance is significant due to the low discharge energy. The stray capacitance changes as tool electrode size changes, thus affecting machining performances; this is the so-called scaling effect in micro-EDM. The effects of tool electrode size on surface characteristics tend to be ignored although it is significant. In this study, micro-EDM experiments were conducted using tool electrodes with different diameters. When machining with lower energy, the tool electrode size exerted significant influence on surface roughness and material migration-scaling effect was significant in low energy discharge. When machining in deionized water, this scaling effect was weakened due to larger discharge gap and ability to easily remove the melted material. The results presented here may provide a better understanding of micro-EDM scaling effect in aspect of surface topography, as well as a reference for building accurate machining performance prediction models of micro-EDM.