Fundamental Research On The Application Of Electrochemical Machining To All-metal Screw Drill Stator

The all-metal screw drilling tool stator has broad application prospects in drilling operations such as deep wells,ultra-deep wells,and geothermal wells because of its high temperature resistance different from that of traditional bushing screw drilling tool stators.However,the inner hole of the stator of the all-metal screw drilling tool is a complex internal spiral deep hole with a large length-to-diameter ratio,a complex structure,and a large material removal allowance.Traditional machining has problems such as low processing efficiency,severe tool wear,and high scrap rate.Electrolytic machining is a method that uses the principle of electrochemical anodic dissolution to achieve rapid erosion of metal materials.It has the advantages of high processing efficiency,no cutting stress,and good surface quality.It is important theoretical research significance and practical application value to carry out research on electrolytic machining technology for all-metal screw drilling tool stators.This paper focuses on the problems of poor processing stability,easy short circuit,low machining accuracy,and long cathode development cycle in the electrochemical machining of the stator of all metal screw drilling tools.The main content is as follows:First of all,in order to solve the problem of uneven flow field in electrolytic machining of all-metal screw drilling tool stator with large length-to-diameter ratio,which leads to poor processing stability and easy short circuit,a cathode type based on the inner contour curve parameters of the full metal screw drilling tool stator is proposed.Based on surface design method,a mathematical model of small-gap electrolytic machining flow field was established,and the influence law of the cathode surface on the distribution of gap flow field was studied.The gap flow field structure was optimized through small-gap flow field simulation,and finally the surface curvature was uniform.The cathode profile is smooth,defect-free and abrupt,and the complex cathode profile is designed.Secondly,in order to solve the problems of low forming precision,long cathode development cycle and high cost in the electrolytic machining of the stator of the all-metal screw drilling tool with a large length-to-diameter ratio,the closed-loop design idea is adopted to put forward an electrolytic machining forming prediction method based on the particle swarm optimization BP neural network,and the network structure is optimized to complete the electrolytic machining forming prediction of the stator of the all-metal screw drill.The complex mapping relationship between complex cathode and work-piece size is studied,and the precise design of cathode contour with molding prediction error within 0.06mm is completed.Finally,using the designed cathode for electrochemical machining,the experimental study of electrochemical machining process was carried out on the self-developed large-scale horizontal CNC electrochemical machining system,and the influence of processing voltage,electrolyte pressure and cathode feed speed on the surface quality and forming accuracy of the all-metal screw drilling tool stator electrochemical machining was analyzed.Under the process parameters of voltage of 19V,15%Na Cl+10%Na NO₃ composite electrolyte,electrolyte pressure of 1.6MPa,electrolyte temperature of 35±1℃,and feed rate of 10mm/min,the stator of the all metal petroleum screw drilling tool with a length of 4m can be stably and reliably machined.The dimensional accuracy of the work-piece reaches 0.06mm,and the surface roughness of the work-piece is Ra0.781μm.