CNC EDM of linear and circular contours using plate tools

Electro discharge machining (EDM) is well established for producing complex and deep 3D shaped cavities in hard materials. This traditional (or plunge) EDM process, however, has certain disadvantages. Initially, there is the expense of producing the 3D shaped tooling. Often three male tools are needed termed rough, semi-finish and finish and these can be quickly worn. Replacing these tools can then be quite expensive. Furthermore, the tool/workpiece gap configuration often results in flushing difficulties; short circuit damage and high relative electrode wear (REW). Today CNC EDM machines can provide opportunities for using simple tools to produce some of these 3D cavities. This paper commences by outlining earlier research, published by the authors, within this field. It then describes some simple plate tools, employed in this research, and indicates a few practical limitations. A CNC EDM machine is used, with the tooling, for the generation of linear and circular 3D cavities and the machining characteristics are extensively analysed and discussed. These results include material removal rates (MRR), REW, machining area and tool velocity. Finally, the plate tools are compared with 3D form tools showing better surface integrity and an overall cost benefit.