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

近来，许多电和光电装置的尺寸已经减小，并且在这些装置中使用的印刷电路板也已经要求更小。因此，必须减小用于将电气部件固定在印刷电路板上的小孔的直径。针对高速电主轴在印刷电路板上加工小孔的需要，设计了一种带螺旋槽的水润滑圆锥静压轴承。与油基静压轴承相比，水润滑静压轴承在高速运行时具有更低的功率消耗，并且不存在环境问题。此外，由于水的不可压缩性，可以使用更高的供应压力，因此这种轴承具有比空气静力学轴承更大的负载能力。研究人员已经研究了高速主轴水润滑圆锥轴承的轴承特性。在本研究中，开发了一种使用该轴承的高速主轴。测量了各种轴承性能，如旋转精度、承载能力、刚度、扭矩和温升。结果表明，所研制的主轴具有优良的性能，可用于钻床。此外，进行了140，000rpm速度下的钻孔试验，因为对于这种主轴来说，能够实现高精度的孔形状和孔位置是重要的。试验结果表明，所研制的主轴具有良好的钻削性能。

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.