Research On Bipolar Pulse ECM Technology Based On Passive Tool Electrode

Electrochemical machining realizes the processing of parts by ion removal.In theory,it has the potential of high-precision machining,and there is no machining force and tool loss,and it is not affected by the hardness of the workpiece,so it is very suitable for micromachining.However,in actual electrolytic machining,because of the good conductivity of the electrolyte,it is difficult to control the electrolytic reaction to occur in the designated processing area on the surface of the workpiece,resulting in stray corrosion,resulting in low machining accuracy and limiting the use of micro-electrolysis in actual machining.Micro electrochemical machining is often carried out by milling,and the tool shape is mostly a rodshaped cathode.Insulating the side wall of the rod-shaped cathode is one of the effective measures to improve the precision of micro electrochemical machining.For solving the defect that the coating is easy to peel off under the commonly used coating insulation method,a new idea was proposesd that using a passive tool electrode,a bipolar pulse power source with independent adjustable positive and negative voltage,duty cycle,and frequency for micro electrochemical machining.Under the action of the negative pulse,the insoluble highresistance electrolysis products produced on the cathode surface are adsorbed on the side wall of the cathode to form an adaptive insulating layer.The side surface of the cathode no longer produces electrolysis on the workpiece,avoiding secondary corrosion of the workpiece,thereby improving the precision of electrolytic machining.The following work was mainly carried out:(1)The electrochemical machining process including the electrochemical reaction process,diffusion mass transfer process and surface transformation process are introduced.The chemical reaction mechanism under the positive pulse period and the negative pulse period is analyzed and studied.(2)A micro electrochemical machining machine was built.According to the characteristics of the micro electrochemical machining process,a three-axis micro electrochemical machining platform was built,including the machine tool,power supply,control system and observation device.(3)According to the technical requirements of the bipolar pulse electrochemical machining process,a high-frequency bipolar pulse power supply is designed.The voltage,duty cycle,frequency,etc.of the positive and negative pulses can be adjusted independently.(4)The orthogonal experiment method was used to analyze the influence of voltage,pulse frequency,duty cycle and other parameters on the localization and processing efficiency,and the processing efficiency and processing localization of bipolar pulse and unipolar pulse ECM are compared.