Design of High-speed Wear Lifetime Tester of the Instrument Ball Bearings

Abstract

The instrument ball bearings are the key components of movable components for various kinds of measuring and control instruments; they often operate in the environmental condition of high-speed and light preload. In general, the non metal, disposable oilimpregnated retainer material has been used for these kinds of high precision miniature bearing. The engineering practice shows that the common failure mode of them is the wear which appears under the condition of insufficient lubrication condition. As the results, the vibration and noise will be enlarged, so does the frictional torque, which makes the ball bearings to lose its original working accuracy. It is the lifetime test of bearings that can enable the designers and manufacturers to chose the material of the bearing properly, optimize the product structure, mend the manufacturing technique process, and to enhance the technical level of the bearing products significantly. In this paper, the wear lifetime tester has been designed according to the requirements of the life test for the instrument ball bearings, which consists of the main body of tester, electric system, drive unit and computer measure and control system, etc. The motor spindle has been selected to drive the device which is supported by the aerostatic bearing; frequency conversion speed adjustment mode, its scope of rotating speed is between 0 and 10,000 rpm. A pair of bearings can be tested under the pure axial preload condition, the maximum load is up to 50N, the control accuracy is ±2%; the scope of temperature control is up to 200°C. The variation of frictional torque on the bearing couple will be measured by an online torque transducer. The variation of power dissipation can be monitored under arbitrary speed by use of an on-line high-precision power meter. The wear and quality situation of the contact surface of the bearings will be reflected on these two parameters. Meanwhile, the values of temperature and vibration will also be monitored respectively as the accessorial parameters to assess the real quality of the bearings. Experimental results show that this tester has the capable of presetting load, rotating speed and temperature; monitoring the raise of the temperature and vibration of each bearing, frictional torque and the power variation of the apparatus automatically, these parameters can also be saved as a datum file into the computer at the same time. The developed tester can be used to carry on wear lifetime test, it is suitable for various kinds of instrument ball bearings with different structure and dimension which have been applied for different working conditions, it realized the self-service, intelligent management of the test, and provided a basis for the implement of the lifetime and reliability test to the instrument ball bearings.