A magnetic suspension spindle system for small and micro holes EDM

Due to the slow response of the traditional servo system, short circuit and electrode bending often happen in small and micro holes electrical discharge machining (EDM); these issues usually reduce productivity and the machining quality. To address these issues, a magnetic suspension spindle drive method is proposed. The main object of this paper is to introduce the principle of magnetic suspension spindle drive, the hardware solution of the gap discharge state detection system and spindle control system, software design, and control algorithm of the detection and control systems, and the comparative experiments. Test results of the magnetic suspension spindle performance show that the axial response frequency was greater than 150 Hz, which was faster than that of traditional ball screw servo system. By means of the comparative experiments based on different servo system or different response frequency, it was found that compared with the traditional ball screw drive, small and micro holes EDM based on magnetic suspension spindle drive had the advantages of faster machining speed, less electrode loss, and better machining accuracy (size, shape, taper, and recast layer thickness) The reason is that with the increase of axial response speed, the removal of debris and conduction of heat energy would be speeded up by working fluid, and it would help to eliminate short circuit and improve machining speed and quality. The experimental results also demonstrate that the magnetic suspension spindle system based on the real-time detection method and variable integration of incremental proportional integration differentiation (PID) algorithm has better performance than that of the traditional detection system and ball screw servo system.