Research On Precision Ball Machines' Pressure System

Precision ball is one of key parts in precision rolling bearing manufacturers,and widely used in precision machine tools and testing equipments.Load is considered as one of the most important processing parameters that plays an important role in surface finish and sphere error,but traditional ball machines' hydraumatic pressure system can't control the pressure accurate,and will impact the quality of the finished balls.To overcome limitations in traditional ball machines' pressure system,a new mechanical pressure system is developed in this paper.In order to make the pressure system satisfied demand of precision,the error source of pressure system is analyzed;and the structure of pressure system is optimized.In order to determine the pressure system's precision requirement,the minimum pressure equation is analyzed under the condition of no slipping,and the friction-wear characters are tested.The pressure system's precision requirement is 0.86%F S after calculating.In order to satisfy the pressure system's precision requirement,a new mechanical pressure system is developed.And based on the result of the measurement and the mechanical models of pressure system,the error source of pressure system is analyzed.The analyses indicate that the static friction force is the main error source of pressure error and the vibration of balls is the main error source of control error.On the basis of error source analysis,two improvements of the lapping plate's level optimization and the spring groups' redesigning are made on the pressure system.And the spring groups are evaluated synthetically through statics and dynamics simulation;the analyses indicate that pressure system has best pressure homogeneity and stability when the spring groups has 6 springs and install location at 180mm.After measure the improved pressure system,the accuracy of pressure system is 0.67%F·S,which is satisfied the requirements of pressure precision.In order to verify the property of the improved pressure system;a lapping experiment for G10 level Si3N4 balls is done by using lower loading is operated,and the result show that the yield above G5 level for precision ball reached 93%,the yield above G3 level for precision ball reached 72.5%,and the quality of the finished balls are better than domestic products which processed by traditional pressure system.