Papers by Author: Yun Li

Abstract: The wear mechanism of solid lubrication bearing in vacuum environment was researched. It experiment on the angular contact ball bearing of sputter-deposited MoS2 solid lubrication coating in bearing friction test device, and the time-varying characteristics of bearing temperature and vibration can be got. The MoS2 solid lubrication coating on bearing surface was gradually wear in the process of bearing rotation, and the temperature and vibration of bearing were increased. The transfer membrane was formation in bearing raceway with the increase of bearing rotation. The transfer membrane accumulation occurs due to uneven thickness of MoS2 solid lubrication coating, and the bearing produce serious vibration. Through the microstructure observation and energy spectrum analysis of the bearing surface, it finds there are pitting caused by fatigue wear and scratch caused by abrasive wear after test. The test result indicate that the wear mechanism of solid lubrication bearing in vacuum environment were fatigue wear of solid lubrication coating caused by steel ball circularly rolling and abrasive wear caused by steel ball sliding.

Abstract: The geometric error is the important aspect of affecting the process accuracy of NC machine. In order to improve the machining accuracy, the article gives a new method to compute the cutter path by making use of the error model of MAKINO based on multi-body theory. By comparing the errors which is not divided with the errors that is divided, the study shows that dividing the errors into different regions is an effective method that can improve the accuracy of machine tools. Combing the new method and the error compensation based on multi-body theory, the error partition can be easily used in the compensation of machine tools by modifying the G code.

Abstract: According to the problems of hydraulic system of sway machine, such as commissioning and maintenance are inconvenient, impact of change direction is big, system speed is slow, production efficiency is low, etc. It used electro-hydraulic proportional control valve to improve design in hydraulic system of sway machine. Application of electro-hydraulic proportional control valve has realized automatic adjustment of the hydraulic motor speed; it is effective to solve variable speed movement of sway machine frame and no impact of changing direction smooth. Commissioning and maintenance of sway machine are more convenient, and it improves performance of sway machine.

Abstract: The focus of this paper is to find a new method analyzing the reasons of CNC machine tool precision recession. The modeling of the movement error of CNC machine tool is one of the most important problem for kinematics designing and accuracy analysis. In this dissertation, this study analyzes the six movement error parameters of guide and the model of the guide which including foundation deformation, material’s natural ageing and way rub has been established. A detailed example is given for the modeling precision recession of 3-axis CNC machine tool.

Abstract: According to the multi-body system theory and geometric topology analysis method, combining the geometric structure and working principle of thread NC grinder, made the kinematics analysis for each parts of NC grinder. And the mathematical model for geometric topology structure of grinding machine system was established; the precision machining equations of NC grinder was deduced. Furthermore, the paper used the coordinate transformation principle of homogeneous to deduce the precision processing equation of NC grinder, all of that was based on the moving relationship of the machine tool, the workpiece and the grinding wheel, and got a kind of method that it can use multiple line grinding wheel to grind small radius, small screw pitch and multiple thread. This method laid a theoretical foundation for NC grinder machine processing which used multi-line grinding wheel to grind threads, and improve the grinding efficiency and precision of multi-line grinding wheel; in addition, this method has obtained good effect in grinding thread production.

Abstract: Through analyzing the shape of screw of oil extraction progressing cavity pump, the spiral surface equation of screw was established; and from the relative motion between formed milling cutter and screw, the basic profile equation of formed milling cutter was established with the method of non-instantaneous envelope. According to the actual use of formed milling cutter, aim at the problem of wear for formed milling cutter, established profile equation of front cutting edge and constant back cutting edge, and finally to get a complete profile equation of formed milling cutter. The correctness of milling cutter profile is ensured by interference checking for profile equation of formed milling cutter. The profile equation of formed milling cutter provides a theoretical foundation for the design and manufacture, and it would have great significance to the actual production.