Analysis Of Dynamic Characteristics Of CNC Machine Tool Structure During Working Space Based On Multi-axis Excitation Technology

Because of the huge components, huge workpiece and processing load, the dynamic characteristics of heavy duty machine tool will change with the processing position changing. Therefore, the study of dynamic characteristics of machine tool in the whole working space is important for the guidance of mechanical processing and improvement of machining quality and efficiency. The disadvantages of existing method are following: Firstly, the heavy duty machine tool is assembled by a lot of components, its mode always show directional. The existing excitation method can only give excitation in one direction. Secondly, the working space of machine tool is a continuous zone, but the times of experiment is limited, so the space should be divided properly. Then, massive modal parameters can be obtained by modal experiment in the working space, a proper method that can show all the parameters should be proposed. Finally, the modal parameters is just intermediate parameters, can’t be used to judge the dynamic characteristics of machine tool directly. An analysis method for dynamic characteristics of CNC machine tool in the working space is demand.Considering the disadvantages of the existing method, the main research contents of this paper including the following aspects:(1) Based on the self-excitation method, the multi-axis excitation technology is proposed and applied to the heavy duty machine tool, the machine tool is sufficiently excited.(2) The working space is divided by the stiffness of axis, the stiffness of axis is lower, the axis will be divided into more parts. On the contrary, the axis will be divided into less parts.(3) The working space is divided into several slices, the coordinate is used to show the parameters by slice.(4) A new method based on modal mass distribution matrix to evaluate the dynamic characteristics of machine tool is proposed. The method can quantify the dynamic characteristics using modal parameters.The result shows that the different components of the machine tool present different weakness levels at the same mode, whereas the same component of a machine tool shows different weakness levels at different modes. With the position of machine tool changing in the working space, the weak components of the machine tool structure will change.