An on-line technique to monitor running-in of plain grease-lubricated bearings

Abstract In a well-prepared plain bearing running under the designed conditions, the two surfaces will be separated by a hydrodynamic film of lubricant. It is, however, expensive to lap or to polish the surfaces before assembly, so the bearing usually requires careful running-in to remove the surface roughness left by machining. During this period intermittent close metallic contact will occur. It is desirable to optimize the speed and load conditions so that there is as much surface interaction as possible without danger of gross damage or overheating. In the course of an investigation of suitable control processes it was found necessary to monitor the progress of running-in without removing the bearing to measure the actual surface roughness. A simple on-line method based on the electrical voltage across the thin dielectric film of lubricant was developed. This shows clearly the progress of running-in and can be used to indicate automatically the achievement of a satisfactory smoothness. The associated equipment can be produced inexpensively and can be incorporated in a microprocessor monitoring system.