Dynamic Characteristics Analysis Of Spindle Parts For The Thread Repair Cnc Lathe

With the rapid development of the technology of machine tool design, the consumers put forward higher requirements for machining performance of the machine tools. The thread repair lathe is widely used in the petroleum drilling industry, and the dynamic characteristics of spindle parts directly affect the machining precision of the workpieces. This paper mainly studies the dynamic characteristics for the spindle parts of the thread repair CNC lathe, in order to lay the foundation to make further improvements for the processing performance.First, in this paper, the design method of machine tool dynamic characteristics and the development trends of the study on the dynamic characteristics for the machine tools spindle parts were summarized, finite element modal analysis theory applied on mechanical structure dynamic characteristics research was introduced. Second, the dynamic characteristics for the spindle parts of the thread repair CNC lathe was based on finite element method. When analyze the dynamic characteristics for spindle, the important influence of the dynamic characteristics was considered, the bearing supporting stiffness for the spindle parts of the lathe was calculated by the calculation formula of bearing stiffness. The dynamic characteristics and dynamic response of the spindle under unrestrained and the bearing stiffness were analyzed by finite element method, the natural frequency, modes and the critical speed were gained, and these data indicates the spindle structure will not cause resonance. Again, hammering method was carried on to made the dynamic analysis for the spindle, and the natural frequency and vibration modes under the free state and the first natural frequency of the spindle under the assembly state were gained. It turns out that the natural frequency and the modes of the spindle under the free state was closed to the FEA results, but the natural frequency under the assembly state differ considerably from FEA result. Finally,the error was analyzed, based on the natural frequency of the spindle under the assembly state, studied the influence to the dynamic characteristics of the spindle under the bearing stiffness, support span and the spindle radial size, and made the optimization for the spindle structure.Research results show that the finite element method can relatively predict the dynamic characteristics of the mechanical structure at the beginning of the design, provide theoretical basis for structure optimization design, and be a kind of effective and feasible design method in the actual project.