Investigations on reduction of tool electrode wear in micro-EDM using novel electrode materials

In micro-electrical discharge machining discharge energies of less than W-e = 100 mJ per single discharge are used. Due to the short pulse durations in micro-EDM the tool electrode is usually charged as cathode to reduce tool electrode wear. Nevertheless, compared to conventional EDM, especially when relaxation generators are used, the relative wear can increase to more than 30%. In order to reduce the electrode wear, novel electrode materials can be applied. Experimental investigations aim to decrease the wear of tool electrodes by using boron doped CVD-diamond (B-CVD) and polycrystalline diamond (PCD). Both materials offer high thermal conductivity and a high melting/sublimation point which are general requirements for tool electrode materials. Until today there is a lack of knowledge regarding the process behaviour of both materials under conditions of micro-EDM with respect to the relative high specific resistance of diamond materials compared to those of copper or tungsten-copper. This paper gives an insight into latest research results regarding the process behaviour of B-CVD and PCD in micro-EDM as well as influences of electrode materials on tool electrode wear and surface formation processes. (C) 2008 CIRP.