Research On Key Technologies For Reliability Growth Of Ball Screw Pair

As the core transmission component of CNC machine tools,the performance of ball screw pair directly affects the positioning and transmission accuracy of CNC machine tools.After years of reliability engineering research,the comprehensive performance of domestic ball screw has been greatly improved.As an important part of reliability engineering,the reliability growth of ball screw pair undertakes the task of optimization and improvement of design and processing,standardized operation of field use,but there is little research on this aspect at present.Based on the National Science and Technology major project,this paper aims to establish and verify a reliability growth system and evaluation method for different types of ball screws.This paper firstly establishes the reliability growth system of ball screw pair,which is standardized from three aspects of processing,use and test,monitored by reliability growth management,and evaluated by reliability growth index.A complete reliability growth process is constructed.On the basis of the establishment of the system,several key core parameters,such as center hole,surface quality of raceway,preload and installation requirements,were selected to carry out quantitative analysis,and the specific parameter requirements during processing were given.Three key installation methods,including support mode,installation process and pre-drawing amount,were selected to design and test their effects on the integrated performance of lead screw.When the ball screw pair is processed in strict accordance with the reliability growth system,the reliability growth test is used to evaluate that the current accuracy reliability is 5220 h,and the 4500 h target of reliability growth is achieved.Based on this,the reliability test under the installation of CNC machine tools and the corresponding bench comparison test are performed to analyze the effectiveness of the using safeguard measures in the system and the current direction of improvement of the ball screw pair.According to the reliability distribution of the CNC machine tools,the MTBF requirement of the ball screw pair is 16633 h.A corresponding evaluation method is proposed for the reliability growth test,which is divided into a small sample MTBF algorithm and a large sample AMSAA-BISE reliability growth model.The evaluation results show that the test ball screw pair MTBF is 17800 h,which meets the reliability Allocation requirements.