Dynamic Analysis And Experimental Study On High Speed Motorized Spindle

High speed machining (HSM) has become the mainstream of manufacturing for drastically increasing productivity, reducing production costs and improving the product quality. HSM is also a promising advanced manufacturing technology. In the realization of HSM, machine tool generally plays an all-important role and high speed motorized spindle is the key technology for a machine tool. The machine tool equipped with high speed motorized spindle has characteristic of the zero-transmission and simplified of the machine structure. With use of new mechanical structure, the high speed motorized spindle has much better dynamic performance in response to the high demands in this machine. In general, overall performance of high speed machine in terms of the machining precision and productivity is largely dependent upon the performance of the equipped high speed motorized spindle.This thesis is funded by the National Natural Science Foundation, China (No.50675233), Chongqing Municipal Important Science and Technology Key Project, China (CSTC, No.2006AA3010) and Chongqing Municipal Important Science and Technology Key Project, China (CSTC, No.2005AC3029). The dynamic analysis and experiment on high speed motorized spindle are researched. The major contribution of the work is summarized as followings.Due to the high speed motorized spindle system has characteristic of the complex electromechanical system, the view of electromechanical coupling analyses on high speed motorized spindle is put forward. Grounded on the electromechanical coupling dynamics, several physical processes and multidimensional coupling parameters that exist in the high speed motorized spindle system are extracted and summed up. The global coupling relation of high speed motorized spindle system has also been discussed and its frame is given. The physical model of the subsystem is set up based upon the analysis of the structure and local coupling of motor-spindle subsystem in high speed motorized spindle. The mathematical model is developed base on variance principle. The dynamical equation of the subsystem is established and the validation of equation is made by experimental data from the examples.The dynamic analysis is carried out on the high speed motorized spindle with use of the transfer matrix method, which includes the structure simplification and modeling segmentation. Typical elements'states of the shafting are described by mathematical method. For the special structure of the high speed motorized spindle, some state vectors of typical elements in the simplified model are modified. Then transfer matrix model of the high speed motorized spindle, which is also the frequency model of the shafting, is derived. As a case study, the natural frequency and critical speed of the high speed motorized spindle with 60 000 rpm are calculated by the modified model. Meantime the calculation course is also described.On the condition that the transfer matrix method is applied to do the mechanical dynamic analyses of the high speed motorized spindle, mechanical analysis on high speed motorized spindle under the eccentric state is carried out through electromagnetic method. Then the transfer matrix equation for the shafting is set up. Combining the analytic results of electromagnetics and mechanical dynamics, state vectors of typical elements are modified. The transfer matrix equation of the eccentric high speed motorized spindle is obtained. Putting the boundary condition of the entire shafting into the transfer matrix equation, the frequency equation of the shafting is gained. Electromechanical dynamics is used to analyze the eccentric motorized spindle's vibration which caused by the electromagnetic force. Lagrange-Maxwell equation is made use of educing its vibration equation and rotation equation.Based on the theory of mode analysis, a free mode experiment is carried out under the 60 000 rpm high speed motorized spindle in order to acquire the modal parameters, such as natural frequency, damp and mode shape. The experimental results exhibited that modal parameters from the test are matched with the theory calculation. The overall experimental method and procedure are also introduced.Loading and measuring the load applied on a high speed motorized spindle in the non-machining state is an important issue in performance evaluation of high speed motorized spindle. A new method is developed through modifying a dynamometer to make the loading possible in the experiment. According to the different rotating speed, two types of dynamic loading test ways which are the inter-drag method and the non-contact method are proposed. The structure and principle of the inter-drag loading method are described in detail. The system can not only load to the high speed motorized spindle, but also measure basic parameters of the high speed motorized spindle and present the corresponding curves which make it visible for states of the high speed motorized spindle at different working points. The inter-drag loading system is applied in experiment on the high speed motorized spindle in which the highest rotating speed is 15 000 rpm. The characteristic curve of this high speed motorized spindle is depicted. Analyzing and dealing with the test data, the inherent characteristic and existent problem of the motorized spindle are gained. Proposed method makes it possible to accurately loading on a high speed motorized spindle.