Yoshiaki Kai

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

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.

An air-bearing displacement sensor for nanometrology of surface forms

This paper presents the experimental investigations for performance evaluation of an air-bearing displacement sensor as a measurement system for nanometrology of surface forms by using it. The experimental configuration and some considerations for the air-bearing displacement sensor are described. Then, in order to identify the basic performance of the sensor, a measuring force and displacement output of the sensor are evaluated on a vibration isolated table. The sensor is also mounted on a diamond turning machine to evaluate the surface form of micro structures. A roll workpiece with Ni-P plating surface, on which micro-lens array are fabricated by using a FS-FTS (Force sensor fast tool servo) on the machine tool, is employed as a specimen for measurement.

Dynamic Response of an Air-Bearing Displacement Sensor for on-Machine Surface Form Measurement

This paper presents the dynamic response of an air-bearing displacement sensor for on-machine surface form measurement of micro structures. The on-machine measurement system has some merits in terms of measurement efficiency and re-machining for error compensation after measurement. On the other hand, the performance of the contact type measurement system based on stylus methods is dominated by the dynamic characteristics of the system because the system is subject to random vibrations of the machine tool including the spindle during measurement. Therefore, the dynamic response of the system is useful for analyzing the mechanical vibrations of the practical on-machine measurement system. In this paper, the equation of motion for the air-bearing displacement sensor to the excited input displacement is derived and the displacement behavior of the system by using a PZT actuator is investigated within certain frequency ranges experimentally for identifying the dynamics of the system.