Investigation On The Electrochemical Machining Of Micro-Groove Using Masked Porous Cathode

Micro-groove arrays on metal surface have played an important role in improving the surface friction and lubrication performance of friction pair,improving the heat transfer efficiency of radiator,and changing the surface wetting state etc.Therefore,how to accurately and efficiently process the micro-groove structure has become a hot topic in manufacturing research.Through-mask electrochemical machining(TMEM)is an appropriate method for machining massive micro-grooves at one time,which has the advantages of no tool wear,no stress and no heat affected zone on the machined surface,and no burr etc.In this paper,aiming at some weaknesses such as micro convex ridge phenomenon,serious undercutting,and poor dimensional uniformity along the length in TMEM,a method of electrochemical machining of micro-groove using masked porous cathode is proposed based on the good conductivity and permeability of porous metal.In this method,the mask with a single or array micro-slot structure and the porous metal are integrated into a masked porous cathode.In the process of machining,it is closely combined with the anode workpiece to form a “sandwich-like” structure,so that the closed electric field and independent flow field are formed in each micro-groove machining area.The electrolyte reaches the machining area through the masked porous cathode.Based on the principle of electrochemical anodic dissolution,the micro-groove structure is formed on the surface of the workpiece,which significantly improves the electric field and flow field distribution of the micro-groove machining unit and enhances the machining accuracy of the micro-groove.The main research contents of this paper are as follows:(1)The electrochemical machining method of micro groove using masked porous cathode was proposed,and the characteristics of TMEM were expounded.The electric field distribution of different TMEM methods was analyzed.The “sandwich-like” structure was used to improve the machining accuracy of micro-groove,which eliminated the convex ridge phenomenon in the micro-groove.(2)The multi-field coupling physical models including electric field,flow field,temperature field and reactant transport were established,and the theoretical analysis of mass transfer process in the unit domain was carried out for the electrolyte flow modes of lateral flow,forward flow and jet flow.The simulation and experimental results indicated that jet flow mode could enhance the mass transfer process,and reduce the influence of joule heat and bubbles on the material dissolution process,and obtain high electrical conductivity and current density on the machined surface,thus the dimensional uniformity of micro-groove was improved.(3)The electrochemical machining experiment of micro groove using masked porous cathode was carried out,and the effects of electrolyte flow mode,pulse duty cycle,machining voltage and nozzle reciprocating number on the dimensional uniformity,machining localization and machining quality of micro-groove were studied.The results show that the jet flow mode can enhance the mass transfer effect.The low pulse duty cucle and multiple nozzle reciprocating number were helpful to promote the discharge of insoluble products,bubbles and heat in the machining area,and improve the dimensional uniformity along the length and machining accuracy of the micro-groove.Finally,the micro-groove array with length of 20 mm,width of 330 ?m and depth of 45 ?m was fabricated by optimizing the process parameters.(4)In order to improve the machining localization of electrochemical machining used masked porous cathode,the influence of different kind masks(insulated mask and metallic conductive mask)on the electric field distribution of the machined surface was explored.The simulation results showed that the introduction of the metallic conductive mask could weaken the electric field intensity at the edge of micro groove,and reduce the undercutting of micro-grooves.The experimental results also showed that by using the same mask slot width(200 ?m),when the machining depth was 45 ?m,the width of micro-groove with insulated mask was 319.4 ?m,but that with metallic conductive mask was just 227.3 ?m,the machining localization of micro-groove was significantly improved.