Study On Non-contact Rotating EDM System

With the increasing demand for small parts and the wide application of high hardness materials,the traditional production and processing methods have many difficulties in achieving the production requirements.Special machining methods such as Micro EDM have their unique principle of removing materials which are different from traditional cutting methods.Because of its non-direct contact with cutting force andthe processing energy can be adjustable,it has gained more application and attention in many industrial fields.But because the micro EDM scale is very small,especially in the high aspect ratio holes machining,inter-electrode working fluid circulation difficulties and directly affects the stability of discharge,thus reducing efficiency and increasing the loss of the electrode.The disturbance caused by rotation of the electrode can improve the fluidity of the inter-electrode medium and promote the stability of the discharge state.The electrode rotation can disperse the discharge position and effectively avoid the spark concentration and the abnormal arc generation.As the traditional power supply way to use carbon brush or slip ring power supply,this contact type power supply system has the problems of wear,carbon deposition,leakage and electrical spark at the contact point,which restricts the improvement of the electrode rotation speed and the potential safety hazard.The non-contact power supply method can effectively solve the above problems and provide the conditions for the high speed rotation of electrode.In this paper,a small non-contact rotary EDM machine tool is built.Its characteristic is that the electrode power supply adopts the contactless power supply based on the electromagnetic induction principle.According to the needs of the rotary motion of the electrode,a suitable loosely coupled transformer structure is selected and established the equivalent analysis model.Because of the loosely coupled transformer primary side and secondary side clearance between increased the magnetic flux leakage and the leakage inductance,reduces the coupling coefficient and the transmission efficiency,so the circuit compensation structure has been analyzed.Mechanical movement part of the selection of the servo motor with ball screw drive and the full closed-loop control mode.The motion control system is the core of the high performance Clipper motor control card produced by Taidao company.The man-machine interface is written on the IPC,and the Ethernet is connected with the Clipper motion control card to realize the dual CPU control mode.Realization of closed-loop control by adding incremental feedback grating feedback signal to motion platform.Based on Hertz elastic contact theory and Ji-cun-yun-xiao integral method,the dynamic characteristic stiffness parameters of the machine tool joint are analyzed and calculated,and the dynamic characteristics model of the machine tool is established by the equivalent of spring and damper.The natural frequency and vibration mode of the machine tool are analyzed and extracted by Abaqus software,which provides the basis for the prediction and analysis of the static and dynamic characteristics of the machine tool.