Acoustic roller bearing diagnosis in a closed-loop quality control system

Today manufacturing companies face highly competitive quality standards in national and international markets. The design of closed-loop quality control systems is a decisive tool helping to convert the knowledge, gained in the individual measuring and control processes, into effective quality measures. In the car industry, the customer often complains about unusual noises caused by the car bearings or that cars are affected by premature failure due to defective roller bearings. To the car manufacturer this means high warranty costs and the customer is left with a bad image of the firm. A method to diagnose defects of this type was developed and field tested. It is used in the final testing of gearboxes for potential bearing noises and identifies those components of the roller bearing which cause the noise. To this end, a section of a structure-borne noise signal received synchronously with the angle of rotation is converted into an envelope spectrum. The test stand computer generates patterns from the kinematic frequencies of the roller bearings present in the gearbox. These patterns are correlated with the spectral lines of the envelope spectrum. The diagnosis and the feedback from the data base identify the exact built-in location of the bearing, the type of bearing concerned and the manufacturer of the defective roller bearing. The defect can now be purposefully eliminated, thus reducing the cost considerably.