Preliminary experimental study on a servo control strategy for dry electrical discharge machining

Traditional liquid electric discharge machining (EDM) emits huge amounts of carbon, and the process is not environmentally friendly. The emergence of electric discharge machining in gas, or dry EDM (DEDM), has opened up new possibilities for sustainable development of EDM. However, problems of poor discharge stability and low machining efficiency have restricted its application. Considering that servo control is an important factor affecting the discharge state and machining performance, and noting that related research has rarely been reported, we studied servo control of DEDM to understand its features and to improve discharge stability and machining efficiency. The relative discharge ratio, machining efficiency, electrode wear, and surface roughness using different control strategies (proportional–integral–derivative, modified servo control, and conventional control strategies) were compared and analyzed using a custom-made ball screw EDM servo system, and we obtained effective improvement compared with using traditional servo strategies in DEDM. The proportional–derivative control strategy improved the effective discharge ratio by 40.4% and machining efficiency by 136.55% compared with conventional control strategy values. We also analyzed the servo characteristics under different gas media (oxygen, nitrogen, and argon) and proposed a servo optimization scheme. Experimental results verified the effectiveness of improving DEDM by using our servo strategy, indirectly proving the matching characteristics of different media and servos in EDM.