Effects of Some Process Parameters on the Impulse Force in Single Pulsed EDM

Abstract

Electrical discharge machining (EDM) gets the advantage of less cutting force. However, a transient force named the impulse force exists in the machining process. The impulse force has effects on the efficiency, stability and accuracy of EDM. The peak current plays a major role in the impulse force, which has been studied and verified. However, the effects of other process parameters on the impulse force are lack of systematically study. Five single-factor experiments adopting different dielectric medium, polarity, gap width, tool geometry, and immersion depth, were designed and carried out. The single pulsed power source used in the experiments had constant discharge durations by detecting and shutting discharge current, which made the experiments to get rid of the randomness of discharge durations and be accurate. However, the vibration characteristics of the force sensor were changed by the dielectric medium, the fixture and the electrode weight, which made the measure of the impulse force to be complicated. The force balance method was simplified and adopted to acquire the maximum impulse force. It was found that these machining parameters had effects on the impulse force. There was little impulse force when the dielectric medium was air. The impulse force of positive polarity was a little higher than that of negative polarity. The impulse force of sphere tools was larger than that of needle tools. The increasing of gap width or immersion depth enlarged the impulse force. Moreover, the gap width had effects on the crater diameter while the depth of immersion did not. It is verified that these process parameters affected the impulse force by their effects on the bubble.