DEVELOPMENT OF HIGH-SPEED PRECISION SPINDLES FOR DRILLING MACHINES USING WATER-LUBRICATED CONICAL BERAINGS

近年来，许多电气和光电设备的尺寸已经缩小，这些设备中使用的印刷电路板也被要求更小。因此，印刷电路板上用于固定电子部件的小孔的直径必须减小。设计了带螺旋槽的水润滑静压圆锥轴承，用于高速主轴在印刷电路板上钻这些小孔。与油基静压轴承相比，水润滑静压轴承在高速下具有更低的功耗，并且不存在环境问题。此外，这种轴承具有比空气静力轴承更大的承载能力，因为由于水的不可压缩性，可以使用更高的供应压力。研究人员已经研究了一种用于高速主轴的水润滑圆锥轴承的承载特性。在本研究中，使用所提出的轴承开发了高速主轴。测量了轴承的各种性能，如旋转精度、承载能力、刚度、扭矩和温升。试验结果表明，所研制的主轴在钻床上具有优良的性能。此外，由于这种主轴能够实现高精度的孔形状和孔位置，因此进行了140,000 rpm转速的钻孔试验。试验结果表明，所研制的主轴具有良好的钻孔性能。

Recently, the size of many electric and photo-electric devices has been reduced and printed circuit-boards used in these devices have been also required to be smaller. Accordingly, the diameters of small holes for fixing electric parts on the printed circuit-board have to be reduced. Water-lubricated hydrostatic conical bearings with spiral grooves were designed for high speed spindle to drill these small holes on printed-circuit boards. Comparing with oil-based hydrostatic bearings, water-lubricated hydrostatic bearings have lower power consumption at high speeds and do not have the environmental problems. In addition, this bearing has larger load capacity than aerostatics bearings since higher supply pressure can be used due to the incompressibility of water. Researchers have already investigated the bearing characteristics of a water-lubricated conical bearing for high speed spindles.In this study, a high speed spindle using the proposed bearing was developed. Various bearing performances such as rotational accuracy, load capacity, stiffness, torque and temperature rise, were measured. It was found that the developed spindle is excellent performances for drilling machines. Furthermore, drilling test at speed of 140,000 rpm was performed because it is important for this kind of spindle to be able to achieve high accuracy of hole shape and hole position. From this test, it was clearly demonstrated that the developed spindle can achieve excellent drilling performances.