Development of Ultra High Precision Bearing Mechanisms

在精密测量仪器和分度机中，多角轴和孔被用来制造特殊的轴承机构。在著名的“TALKER ROUND”的轴承机构中，下部采用球形，上部采用三点接触式。这些多边形形状对于振动特性和抗旋转是有益的。研磨是一种提高圆柱轴和圆柱孔圆度精度的精加工方法。然而，很少有发表的理论分析的精加工机制，高精度多边形截面。本研究提出了两种加工椭圆形、三角形、四凸形等多边形孔的方法，一种是采用“规则多边形搭接”，使不圆度的傅立叶分量幅值保持不变，而其它分量幅值减小。通过另一种方法，可以使用通过应用“三脚架”圆度测量方法生产的特殊类型的研磨工具来增加任何傅立叶分量的振幅。使用其中一个三脚架研磨工具，四个突起组件的大小从7.64 μ m增加到8.27 μ m，而其他组件则减少。不圆度从约40 μ m改善到约30 μ m。通过理论分析，提出了一种新的研磨方法，即“三脚架研磨法”。

In the precision measurring instruments and dividing machines polygonal shafts and holes have been used to make specially-made bearing mechanisms. In the bearing mechanisms of the famous "TALYROUND", spherical shape for lower part and three-point-contact type for upper part are used. These polygonal shapes are good for vibration characteristics and anti-whirling. Lapping has been used as a finishing mechanism to improve roundness accuracy of cylindrical shafts and holes. However, little has been published on the theoretical analysis of the finishing mechanism for high precision polygonal cross sections. This research offers two methods for finishing polygonal holes, whose shapes are ellipsoidal, triangular, four-protrusion and so on. By one method, the amplitude of the interest Fourier component of out-of-roundness keep constant, while the other components are decreased, using "regular polygonal lap". By the other method, the amplitude can be increased for any Fourier component using special types of lapping tools produced by applying the "Tripod" roundness measuring method. Using one of the tripod lapping tools, the magnitude for the four-protrusion component was increased from 7.64mum to 8.27mum, while the other components were decreased. Out-of-roundness improved from about 40mum to about 30mum. This study shows that any component of the out-of-roundness can be increased, based on a theoretical analysis, as a result many improvements on the new lapping methods, called "tripod lap".