Study on Self-excited Vibration of Wire Electrode in Wire-EDM

This paper describes the self-excited vibration of the wire electrode in wire electrical discharge machining (WEDM) caused by the synchronized variation of the discharge repetition rate.To investigate the correlation between wire vibration and discharge occurrence, wire displacement and discharge current were measured using an optical sensor and current sensor respectively.It was found that frequencies of the wire vibration agree with those of the variation of the discharge repetition rate, and that the discharge repetition rate is higher when the wire approaches the workpiece compared to when it is distancing away from it.However, since the bubble continues to expand even after discharge completes, the impulse of bubble explosion force acting on the wire is greater when the wire is distancing away from the workpiece compared to when it is approaching it.Thus, since the direction of the force is equal to that of the wire movement, the bubble explosion force provides kinetic energy to the wire for every vibration cycle, resulting in the self-excited vibration of the wire.