On-line selection of rough machining parameters

In order to achieve high removal rate and low electrode wear in sinking electrical discharge machining (EDM) a stable machining process is required. The process stability is partly influenced by the contamination of the gap between the workpiece and the electrode. Additionally, it also depends on the size of the eroding surface at the given machining regime. When the eroding surface size varies with the depth of machining, the roughing regime has to be selected on-line. The work presented in this paper shows that the average discharge voltage depends on the eroding surface size. Through sets of experiments at constant machining parameters, varying size of the eroding surface and varying geometry of engaged surface were investigated. The average discharge voltages were calculated on the acquired electric voltage signals in the gap. The average discharge voltage is simple for on-line monitoring and it enables on-line detection of the eroding surface size as well as the on-line selection of the rough machining parameters. Thus the average discharge voltage depends on the geometry of the engaged surface, the prototype of the engaged surface has to be presented to the model for successful selection of the roughing regime as well.