Hayato Yoshioka

Hydrostatic Bearing with High Bulk Modulus Fluid

Hydrostatic bearing systems are used in machine tools due to the high damping capacity, the high stiffness, and the smooth motion. Demands for higher stiff bearing system have recently increased in various industrial sectors. In order to achieve higher stiffness of the bearing system, working fluid with lower compressibility should be used. High bulk modulus fluid with very low compressibility has been recently developed. This paper presents a hydrostatic bearing system using high bulk modulus fluid. The basic characteristics of the bearing are evaluated with an experimental setup for evaluating the bearing system and then compared the degassed oil with the conventional oil. Furthermore, static and dynamic characteristics of the bearing system were evaluated and compared with that of a conventional hydrostatic bearing. Experimental results confirmed that the high bulk modulus fluid enhances the performance of the hydrostatic bearing.

A Thermally Stable High Speed Spindle System Equipped with Self-Cooling Function

Demands for high speed and high precision machining technologies have recently increased in a variety of industries. In general, a high speed spindle system can realize such high performance machining, however it generates a large amount of heat that causes thermal deformation. However, few research papers on thermal deformation-minimized spindle systems have been published so far. This paper presents a newly developed spindle system driven by a built-in air turbine. The developed spindle system has a self-cooling function with the air turbine. In addition, the spindle system has a compact and simple structure compared to the conventional spindle cooling systems. The air turbine was designed to improve the cooling and torque performances. Actual spindle rotational experiments were performed in order to evaluate rotating accuracy and thermal characteristics of the spindle system during rotating at a high speed. Experimental results confirmed that the spindle system can minimize thermal deformation of the spindle by the self-cooling function.