| Computerized Numerical Control (CNC) machine tools, as high technology modern "industrial mother machine", have become important foundation equipment for modern manufacturing technology and equipment industry. Its performance, quality and ownership are important symbols for measuring the modern industry level of a country. Phenomenon of service life degeneration of ball screw, as a key component of the CNC machine tool, would exist during its working process. Well machine tool vibration, work-piece accuracy or pass rate decline could be caused by the service life degeneration of ball screw. Because of the long ordering cycle and high price of the ball screw, much circulating fund could be occupied if a lot of standby parts are purchased in advance. On the contrary, losses due to the long time stop production of machine tool would be more serious, and then, market competition of production company could be affected. Aimed at the above problems, research works as following are carried out in this dissertation:1. Based on the study of relative information and the locate investigation, service life description method of ball screw, in which the working condition of the ball screw and specific requirements of users to the ball screw performance are both considered, is proposed. The description method is more correspond to practical application. Combining with relative national standards, ball screw key performances including precision, friction torque and so on are analyzed, and service life evaluation system of ball screw is also built in this dissertation. Meanwhile, the methods of comprehensive performance evaluation and service life calculation about the ball screw are also given out.2. A test device of ball screw service life accelerated degeneration is researched and built. The axial force of ball screw can be loaded by a servo control system. The test data of ball screw entire life cycle can be monitored and collected by an on-line monitoring system of ball screw service life accelerated degeneration test, which can be a good research platform for prediction technique study of ball screw service life.3. Based on the detective signals analysis in time domain, frequency domain and time-frequency domain, a new method of predicting ball screw service life according to varying features is proposed. The method can selecting features automatically by means of the correlation coefficient. The prediction accuracy is enhanced and the on-line prediction system of ball screw service life can be achieved by this method.4. Ball screw service life prediction model is proposed based on double model framework of online self-learning. The model is provided with the advantages of fast computing and strong portability, and is suitable for ball screw service life online prediction.5. A kind of graphical analysis method for illustrating screw performance degeneration distribution is proposed. By means of this method, the performance degeneration distribution of ball screw each part is shown directly in graphic form. An ocular and reliable maintenance judge, therefor, can be provided, and it is also in favour of increase working efficiency and part machining quality of CNC machine tools.The service life evaluation system, accelerated life degeneration test, detecting signal processing, life prediction model of ball screw are investigated in this dissertation. A number of technical problems in the practical process of ball screw service life prediction are solved, and ball screw service life accurate prediction can be come true. A new thinking for graphic illustrating of ball screw performance degeneration is provided and the research work can enrich and develop the ball screw service life prediction techniques. |
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