Improving surface integrity and surface roughness by forming multi-discharging channels from one pulse in EDM

Abstract

Conventional electrical discharge machining (EDM) usually took a large gap distance to obtain the integrity of machined surface. However, large gap distances really prevented further improving surface quality and lowered machining efficiency as well. Conversely, this paper took small gap distances in discharging so that discharging from multi-discharging channels could be synchronously realized. To this end, a new adaptive control system for EDM was studied in this paper where arcing ratio was chosen to be a control index and gap servo voltage was a control variable. Arcing ratio was forced to follow a predetermined arcing ratio expectation by adapting gap servo voltage so that arcing pulses could not take place in machining and thus the integrity of the machined surface can be obtained. Compared with conventional EDM, in addition to the more integrated machined surface had been obtained, the surface roughness had been lowered almost 3.5 times and the machining rate improved 2.5 times. Additionally, different forms of multi-discharging channels from one pulse were able to be realized by setting different arcing ratio expectations meeting different requirements of surface roughness. The significance of the study is that forming multi-discharging channels from one pulse displayed an innovative approach in precision EDM.