| In recent years,the development scale of numerically controlled machine tool industry has been continuously expanded with the promotion of national policy protection and the development of modernization of machinery industry.Ball screw feed system,as a driving system of CNC machine tools,has a crucial role in guaranteeing and improving the machining accuracy,efficient work and the service life of the whole CNC machine tools.In orders to improve the performance of ball screw secondary and increase the service life of ball screw secondary.From the calculations of preload force of ball screw coupling,load distribution of ball in the raceway,contact stiffness of ball screw coupling,contact wear between ball and raceway,etc.,the contact characteristics of ball screw coupling are investigated in depth.The main investigation contents and conclusions are as follows:(1)According to the Hertz contact theory,the analysis is performed from the preload method and preload principle of the ball screw sub.Calculation method of preload force is examined on the basis of the correlation between the preload structure overload and contact deformation.The comparisons validate the reasonableness of the preload force calculation model and the analysis of the influence of structural parameters on the preload force.The research shows that the preload force of ball screw sub can be calculated by the preload structure interference.(2)Establish the ball bearing distributional model according to the correlation between contact definition and contact angle under the influences of preload force,coupling load,additional turning torques and errors.The analysis of the influence of varied coupling load,rotating torque and error on the ball bearing distribution and the discussion of the influence of coupling force,rotating torque and fault on the fatigue life of ball screw sub.The research shows that: the rotational torque and derivative error have the most effect on the ball load distribution and fatigue life,and the lifespan of ball screw associate is extended by improving the accuracy of ball screw associate in the manufacturing and assembly process to narrow down the influence of combined load,torque and geometric error on the contact load and fatigue life of ball screw associate.(3)When the working load is acted,the compression deformation of the working nut,the recovery deformation of the preload nut and the compression deformation of the preload gasket are studied on the influence of the contact deformation of the ball screw sub,and the influence of the structure parameters on the contact deformation is simulated and verified.When the influence of compression and recovery deformation on contact deformation is considered,the resulting is more close to the simulation experimental results.There is a variation in the contact deformation between the two rollers,and the influence of contact deformation can be reduced by replacing the material properties of the rollers on the side with larger deformation,which can effectively improve the stiffness of the ball screw sub and extending the service life.(4)In addition,the revised Archard theory is used to calculate the contact wear between the ball and raceway,to study the impact of preload force and the accuracy loss due to the contact wear of the ball screw sub,and to evaluate the effects of the structural and mechanical parameters of the ball screw sub on the accuracy loss.The results show that the structural parameters of the ball screw subsets can significantly affect the change of the amount of accuracy loss,and the contact wear on the screw side is larger than that on the nut side.T Contact wear studies are significant for the extension of the life of ball screw subsets. |
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