Dynamic Behaviour of Spindle on Large EDM Machine Induced by High-Speed Jump Motion with Different Control Strategies

Abstract

High-speed jump motion in electrical discharge machining (EDM) has been proven to be an important reason for flexible impact and vibration on EDM machine tools. Especially for large EDM machines, the moving parts possess large mass, and different jump control strategies cause different vibration characteristics. However, little attention has been paid to the kinematic comparison between different strategies, and the effect of jump motion on EDM spindle dynamics behaviour is also neglected. In this paper, the dynamic behaviour of spindle on a large EDM machine induced by high-speed jump motion has been investigated. Control strategies including trapezoidal velocity profile, constant jerk profile and sinusoidal jerk profile are considered. The kinematic characteristics of these jump control strategies and corresponding dynamic behaviour of EDM spindle were studied. As a result, under the same maximum velocity of 80 mm/s and maximum jerk of 128 m/s3, the jump period and height of sinusoidal jerk profile are about 0.05 s longer and 1.2 mm larger than that of the other two strategies, respectively. Trapezoidal control strategy causes the largest vibration amplitude of 48.7 μm on spindle during jump motion and thus the strongest forced vibration. The experimental measurement platform for vibration displacement was established. Comparing simulation and experiment data, the relative error is lower than 14%, which verifies the simulation model. Moreover, it can be found that large jump velocity increases vibration amplitude of spindle significantly during machining. When the velocity is 80 mm/s, the maximum vibration amplitude is 23.0 μm. And large velocity of jump motion makes spindle amplitude attenuate faster.