Characterisation and Experimental Testing of the Properties of Carbon Fibres in Respect of Their Application as Tool Electrodes for Micro EDM

Micro electrical discharge machining (mu EDM) is a technique in which much research concerning the shaping of microstructures has been done. Among others the goal of research is the search for still better materials to use in tool electrodes. One material that might be considered is carbon fibre, especially due to its naturally small diameters and minimal price. Therefore, the investigation of micro electrical discharge machining using carbon fibres as the tool electrode has been undertaken. The properties of the applied material were characterised and are discussed. For the experiments a special design and fabrication procedure was developed for short electrodes based on carbon fibres. Micro EDM sinking with different configurations of electrical parameters was carried out. The results obtained show the possibility of using carbon fibres for tool electrodes but the experiments also revealed some problems. One of them is high whippiness of fibres and in a consequence easy bending. Moreover, it is shown that under electrical discharge conditions, the wear resistance of carbon fibres is very small compared to the best electrode materials, like tungsten or sintered tungsten carbides. Therefore, more complex machining configurations are proposed and discussed, such as the application of longer electrodes or even quasi-continuous filament electrodes.