Experimental Research On Machining Micro Serpentine Spring By EDM

With the rapid development of scientific research and national defense industry,high-tech products are developing towards functional integration,ultra-precision and miniaturization.Miniaturized devices are widely used in biochemistry,clinical medicine,aerospace,military industries and other fields.Conventional EDM technology plays an important role in processing micro structures because of their high precision,little limitation on physical properties of materials and no macroscopic force.Aiming at the actual demand of micro serpentine spring and micro sharp groove structure in a micro device,the experimental research on micro structures processing by conventional EDM equipment was explored,which provides theoretical preparation and key technology support for miniaturization devices.Firstly,aiming at the defect of bending deformation of the serpentine spring(the section size is 0.12mm×1mm,the clearance is 0.25mm)by WEDM,the mechanism of bending deformation of the workpiece was explored.The direction on the workpiece of main forces such as electrostatic force,electromagnetic force,discharge reacting force and hydrodynamic force were preliminarily judged.Then,according to the rectangular cantilever beam cutting test,the direction of the resultant force and relative proportion of the main forces were further judged,clarifying the deformation mechanism of micro structures in WEDM,which lays a theoretical and experimental foundation for fabricating micro serpentine spring.Secondly,the rules of manufacturing micro serpentine springs on 304 stainless steel,pure copper and nickel plates by WEDM were explored.Micro serpentine spring could be fabricated through optimized cutting trajectory and optimized processing parameters,that is,a combination of trajectory control and energy control,along with multiple cutting which can improve the surface quality.Thence,the micro serpentine spring can be fabricated by multiple cutting according to the optimized trajectory to guarantee better surface quality and at the same time the added bracing structure can ensure that the serpentine spring has minimal deformation in WEDM;and then cutting off the bracing structure after eliminating the residual stress by stress relief annealing to reduce deflection,the deformation angle decreases from 16.2°to 3.6°(its’ requirement is range from 0 to 5°).The bending deformation and surface quality of micro serpentine spring are significantly improved.Finally,in order to maximize the shape and positioning accuracy of shape groove,the size of shape-angle electrode and the relative position of each station was reasonably designed on the whole electrode.Experiments on how to fabricate multi-station sharp-angle electrodes that meet requirements were carried out.It is found that multi-station sharp-angle electrode with better surface quality can be fabricated by using lower feed rate,constant speed and multiple cutting by WEDM.The influence of the number of stations and electrode material on the shape accuracy of the shape groove was investigated by conducting experiments on forming 16°groove with copper-tungsten alloy and pure copper electrode by EDM.It was found that the forming accuracy of the copper-tungsten alloy is better because of its low loss performance at the same stations,and the forming accuracy is higher under six-stations.Therefore,the six-stations copper-tungsten electrode can obtain better quality,with a sharp angle of 16.3°(relative error of 1.9%),a forming depth of 0.356mm(relative error of 1.1%)and a good shape accuracy.