Machining Micro-pits Of Working Surface Between Friction Pairs By MicroElectrochemiacal Machining

Electrochemical Machining (ECM) is a processing technology, in which the metallic workpiece as anode is produced based on anodic dissolution in electrolyte. ECM appears to be a very promising metallic micro-manufacturing technology, because the process could machine workpiece ion by ion. Parts with multiple pits have been widely used in reducing the loss of the motor. ECM shows its potential in preparation of parts with multiple micro-pits, due to its unique advantages. The thesis focuses on the key techniques to machining of micro-pits of Cr-electroplated friction pairs by micro-ECM, and the main work is finished as follows:(1) The method to produce multiple cylindrical micro-electrodes by Electrical Discharge Machining(EDM) and the single cylindrical micro-electrode produced by electrochemical etching is proposed. Then multiple cylindrical micro-electrodes with average of 160μm diameter and 1500μm length are prepared, and the single cylindrical micro-electrode with average of 40μm diameter and 1500μm length is produced.(2) On the foundation of the machine tool in being, the micro-ECM system to prepare micro-pits is constructed, including the clamps of the cathode and anode, the circulation system of the electrolyte, and the control of the machining process, and so on.(3) Effects of several process factors, such as machining voltage, pulse duration, duty ratio, composition, and concentration of electrolyte on machining accuracy are investigated. The results show that electrochemical reaction region could be significantly contracted with low machining voltage, short-pulse duration, duty cycle, and low concentration passivity electrolyte. Based on the above experimental results, micro-pits on plate with good roundness and uniformity could be obtained with a diameter of 285μm and depth of 5.8μm with multiple cylindrical micro-electrodes; micro-pits on plate with good roundness and uniformity could be obtained with a diameter of 120μm and depth of 4.8μm with single cylindrical micro-electrode, and micro-pits on cylinder friction pair with good roundness and uniformity could be obtained with a diameter of 85μm and depth of 5.5μm.(4) The result of the experimental shows that the frictional coefficient of the parts with micro-pits is decreased, compared with the pit-free parts.