Key Technologies For EDM Machining Of Difficult-to-cut High-precision Micro-structures

Ultra-precise,precise machining of parts made of difficult-to-cut materials with low rigidity,high aspect ratio and thin-wall structures has been an important problem in the area of current aerospace precision control system.In this paper,we studied a series of key technologies of precision EDM in solving the problem with the machining of typical parts of low rigidity,high aspect ratio and thin-wall structures,such as twist rod and feedback rod.In this paper,a tangential feed method with rotating disk electrode to processing of cone of the feedback rod has been proposed to achieve a goal of processing several feedback rods with one electrode and to compensate the wear of electrode automatically,which can improve the processing efficiency and quality.C-axis indexing methods has been applied on the twist rod,which can help make full use of the automation and improve the positioning accuracy.Analysis on static mechanics,modal shapes and electric field distribution of the feedback rod and twist rod has been conducted with COMSOL Multiphysics,which provides a theoretical basis for finalizing the processing method of the program.The effect of the size of the craters on the surface quality of EDM is analyzed.Based on the analysis of the mechanism of EDM,the effect of the amount of discharge energy on the size of EDM crater was analyzed,and the mathematical model of the discharge erosion was established based on heat transfer theory.Simulations of single pulse EDM crater of the two materials have been analyzed and a relationship of depth and diameter of the crater and the current and pulse width of the discharge energy was obtained.Based on data from simulation of the single pulse EDM crater,EDM characteristics of 3J40 materials with graphite,copper-graphite,copper electrodes and DUR600 with copper electrode have been investigated by experiments,and the relationship of material removal rate(MRR),electrode wear ratio(TWR)and surface roughness(SR)with the current and pulse width was deducted with statistic method,which provide a reference for selection of processing parameters.After analysis of the reason why the cone was hard to be rounded by EDM,a "high-speed part rotation method" has been proposed to solve this problem without modification of gap control.By optimizing the processing parameters,feedback rods and twist rods have been manufactured successfully.