Development of spindle with motor function for ultra-precision machine tool

本研究的目的是开发一种新型超精密机床主轴。超精密机床主轴与传统主轴的区别在于，所提出的主轴使用水流来产生主轴操作的动力。相比之下，超精密机床的传统主轴使用电力。在主轴中，水流被用于主轴的三个重要功能。该主轴具有三种功能：（1）支撑功能：水静压轴承支撑主轴体;（2）马达功能：在主轴体内设计简单几何形状的流道，使水流通过流道产生扭矩以旋转主轴体;（3）冷却功能：温控水使主轴变形最小化。然后介绍了主轴的设计过程。基于该过程，开发了确定最佳参数组合的软件，从而可以获得最高的主轴效率。在这项研究中，最佳参数的设计与以下规格的主轴计算开发的软件。(1)额定转速：（2）额定功率：50 W（3）水静压轴承的额定刚度：50 N/μm。实验结果表明，主轴运行平稳，表明静压轴承和主轴电机的正确操作。此外，实验验证了电机的性能和冷却功能满足设计要求。相比之下，水静压轴承的刚度没有达到规范的水平，主要是由于轴承中的节流器的特性。在未来的工作中，轴承刚度的改善将通过改变直径的限制器。

A purpose of this study is to develop a new spindle for ultra-precision machine. A distinction between the spindle and conventional spindle for ultra-precision machine tools is that proposed spindle uses water flow to generate power for spindle operation. In contrast, conventional spindle for the ultra-precision machine tools uses electric power. In the spindle, the water flow is utilized for important three functions of the spindle. The three functions are the follows;(1) Support function: water hydrostatic bearings support the spindle body,(2) Motor function: flow channels with simple geometries are designed inside the spindle body so that the water flow through the channels generates torque to rotate spindle body, and(3) Cooling function: temperature controlled water minimizes the spindle deformation.This study proposes the principle and structure of the spindle. A design procedure for the spindle is then introduced. Based on the procedure, software to determine a combination of optimum parameters was developed so that highest efficiency of the spindle can be obtained. In this study, optimum parameters to design the spindle with the following specifications were calculated by developed software.(1) Rated rotational speed: 10,000 rpm(2) Rated power: 50W(3) Rated stiffness of the water hydrostatic bearings: 50 N/μm.Experiments were carried out to investigate performances of the developed spindle. The experiments show smooth operations of the spindle, which indicates correct operations of the hydrostatic bearings and motor of the spindle. In addition, the experiments verify that performances of the motor and cooling function satisfy the design requirements. In contrast, stiffness of the water hydrostatic bearings does not reach the level of the specification, due to mainly the characteristic of the restrictors in the bearings. In future work, improvements of the bearing stiffness will be attained by altering diameter of the restrictors.