Dynamic Characteristics of Ultra-Precision Machine Tools (Evaluation for Stiffness of Guideways by Impact Test)

Abstract

This study discuss the dynamic stiffness of guideways of a ultra-precision machine tools. V-V roller guideways have been employed in ultra-precision machine tools, as they can provide very smooth motion and good straightness. Recently, general linear ball guideways are also employed in ultra-precision machine tools. In the design of the machines, it is necessary to obtain the stiffness of these guideways. Therefore an identification method of the guideway stiffness is verified in this paper. In this method, the guideway stiffness is identified from the natural frequency of the moving body. First, the impact test is carried out for an ultra-precision machine tool to obtain the vibration mode of its moving body. Next, a simple vibration model is developed based on the obtained vibration mode to identify the equivalent stiffness of the guideways. Then, the static stiffness of the guideways is measured for the verification of the identified equivalent stiffness. For further verification, natural frequencies of the moving body are calculated by FEM with the identified equivalent stiffness and compared with the measured natural frequencies. The identified equivalent stiffness agreed well with the measured static stiffness. Furthermore, the natural frequencies were calculated almost correctly with the identified equivalent stiffness.