Reliability Sensitivity Analysis And Reliability Robust Design Of Electric Spindle Based On Point Estimation

High-speed machining is a promising advanced manufacturing technology for increasing productivity and reducing production costs dramatically. With the rapid development of cutting tools and CNC technology, more and more mechanical equipments are kept to the high speed, high precision, high efficiency and high intelligence and built-in spindle cell has to be the most suitable one of the core functions of CNC machine tools for the high performance condition. These performances also require the increasing reliability of the spindle system.In the paper, it studies the static characteristics and the reliability of the high-speed, high-power milling machining center’spindle to enhance the re-cutting processing performance. The point estimation theoty is introduced to the reliability analysis and reliability sensitivity analysis based on the reliability theory home and aboad. In order to solve practical engineering problems, this method will be combined with FEA. This research focuses on the following two aspects:The partial differentials of the moment of the performance function with respect to the distribution parameters of the basic random variables are transformed as expections, then the reliability sensitivity is approximately transformed as the expection, by use of point estimation of the first four order of performance function proposed by Zhao and Ono, which can be solved. This method requires characteristic function values and limit state function values in estimated points, in practical engineering problems, which can be achieved through FEA softwares. It must needs to have points group, when FEA softwares are used for this method, In the paper, it gives the method about how to set up the point group. The approximate method needn’t seeking the design point of limit state function equation, and is suitable for the independence of analytical expression of the performance function, non-normal random variable and multiple failure modes, which has broad applicability. In addition, the stability of the reliability sensitivity calculation affected by samples is discussed, by comparing results, it reflects the error sources and how these errors affect them.By analysising the status and development trend of the spindle, re-cutting performance has been studied. First, it calculates the static stiffness of spindle bearing. Secondly, the reliability of the electric spindle is analyzed with the method proposed in the paper. Finally, the sample is known with the point estimating method, through the neural network, and the functional relation between the spindle static stiffness and design variables is approximated for the robust optimal design.