Diagnosis of grease lubricated main spindle bearings

The spindle bearing system is a very critical component with regard to the unexpected failure of a machine tool. While the innfluence of many different operation conditions makes a reliable prediction of the life expectancy of spindle-bearings impossible, after an occured failure a long space of time will be needed for repair. A newly developed diagnosis system detects several critical states at the same time. The procedure serves for the determination of over-lubrication and under-lubrication, ageing of lubricant, pollution of lubricant by coolant or water as well as damage to the race surfaces due to abrasive wear or fatigue. Measuring the temperature at the outer bearing ring while the spindle is accelerating during a test-run is a suitable method for determine changes in the lubrication.