Research On Electrical Machining Technology Of Micro-jet Square Hole

Micro-square holes are important structural forms in micro-holes.They are widely used in aerospace,automobile,high precision servo valves because of high torque,strong guidance and good motion stability.The technologies for the machining of square hole include mechanical machining,high energy density beam machining,electrical discharge machining and electrochemical machining.Due to the limit of tool size,the micro square hole is not easy machined by mechanical machining.In mechanical machining,the tool is easy to wear and tear,and it is difficult to machine high hardness materials.Laser bean machining and electrical discharge machining have heat-affected zones and recast layers on the workpiece.Damage to the workpiece should be avoided in many applications.Compared with other micro machining methods,The advantages of ECM make it eminently suitable for micro machining in aviation and aerospace applications.Researchers have pay more attention to the machining of circle hole in ECM,but the study of fabrication of square hole is little.The study of the fabrication of micro square hole is useful to improve the quality of holes and the perform of machine.In this paper,three methods are proposed for the machining of micro square holes on 321 stainless steel with thickness of 0.1 mm: electrochemical drilling with formed electrode,electrochemical milling and electrochemical discharge machining.The main research contents of the paper are listed as follows:(1)electrochemical drilling with formed electrode: The hole is fabricated by electrochemical drilling with tool electrode jump motion assisted with the micro amplitude vibration of workpiece.The square electrodes were formed by wire electrochemical machining and the size of cross section was 100*20?m.The effects of electrolyte,voltage,pulse duration and electrode shape on electrochemical drilling were explored experimentally.An experimental system was set up and fixture was designed.(2)electrochemical milling: The machining process includes three steps:(i)the hole is first fabricated by electrochemical drilling;(ii)the square hole is then rough machined by electrochemical milling;and(iii)finally the hole is finished by electrochemical milling to reduce the corner radius.The multiple,stepped,cylindrical micro electrode was fabricated by the electrochemical etching technology.In the rough milling,the influence of double pulse and feed speed on ECM is analyzed and the parameters are optimized to improve the efficiency.On the premise of ensuring the stability of machining,the feed rate should be as large as possible.In finishing milling,the effect of voltage,pulse duration,pulse period and feed rate on the corner radius were explored.Finally,the micro square hole was fabricated by electrochemical milling with the optimized parameters.(3)electrochemical discharge machining: In the machining process,first,the square hole was machined by EDM layered milling and then the square hole was modified by ECM.The experiment system for electrochemical discharge machining was set up.The square electrode were fabricated by wire electrical discharge grinding.The experiments were carried out to study the effect of parameters on EDM and ECM.