EXPERIMENTAL-STUDY OF A PRECISION, HYDRODYNAMIC WHEEL SPINDLE FOR SUBMICRON CYLINDRICAL-GRINDING

Hydrodynamic journal bearings have been widely used in various types o f rotating machinery, ranging from heavy duty, high-impact application s, such as the crank shaft of an internal combustion engine and turbin e rotor, to high-precision, light load applications, such as precision spindles in cylindrical grinding machines. Although extensive theoret ical and experimental results have been presented for hydrodynamic bea rings, the available literature seems to be limited for precision hydr odynamic bearing spindles. In this study, practical methods have been developed to quantify the performance of a hydrodynamic wheel spindle operating in the horizontal mode to produce precision parts with submi cron roundness tolerance and very fine surface finish. These methods c an easily and cost effectively be implemented on various machines in a n actual production environment for effective predictive maintenance. The main experimental results show that the long-term drift of the spi ndle at steady state is less than 1 mu m vertically and 0.2 mu m horiz ontally, and the radial error motion of the spindle based on unfiltere d data is less than 1.6 mu m for all the speeds tested. It is also fou nd that the shaft center position (vertical lift and horizontal shift) at the cold condition is substantially different from that in the ste ady-state warm condition. From the results, an optimal spindle speed i s recommended. (C) 1998 Elsevier Science Inc.