The Study Of Hollow Ball Screw Applied In CNC Servo Feed System

The thermal deformation of ball screw is becoming the main factors in the processof development towards high speed, high precision, that It is further to improve themachining accuracy of servo feed system in NC machine tools. The main heat sourcesincluding screw groove and balls, balls and nuts raceway frictional heat, balls and supportbearing inner and outer ring friction heat, electric heating through the coupling of heat ispassed on to the lead screw, environmental radiation and so on. Among, the ball screwfriction heat accounts for large proportion, and especially under the condition of high speedfeed, friction heat is more huger, which will decrease the stiffness of ball screw and thethermal deformation is more bager.Research, therefore, under the condition of high speed, inhibition of ball screwtemperature rise and thermal deformation to improve the machining accuracy of NCmachine tool has the profound significance.For servo feed system, the ball screw heat source is mainly screw nut of heat,therefore this article take the local cooling and cooling combination of comprehensively,namely hollow ball screw in alternative solid ball screw, cooling medium intothe ventilation with forced cooling and design of hollow nut cooling, mutual inhibition ofthermal deformation of hollow ball screw. In addition, the hollow screw ball screw alsohelps to reduce the moment of inertia in the operation of high-speed and increase the screwshaft stiffness and fast responsiveness of servo feed system. The main research content isas follows:For our country study trend and actual situation about Servo system, the paperdetermined the research route of this topic after the analysis of the servo system thedevelopment of thermal compensation and cutting-edge technology. Servo system as awhole system from the point of view, It is the ball screw hollowing to address the stability,accuracy, quickness of the servo system， which is a series of key problems， after further research on the impact of various performance parameters of the CNC servo system and itsinfluence.1, This paper deduces solid/hollow ball screw’s thermal deformation model based onthe theory of Heat Transfer, Thermodynamics and the Finite Element. Then, it is plugged inthe specific parameters of a ball screw machining center servo feed system. As a result, thiseffect is theoretically proved that the hollow ball screw cooling method obviouslysuppresses the thermal deformation of ball screw.2, Under the same conditions, the3D model is established about the solid/hollow ballscrew and its differences of temperature distribution are studied with ANSYS/Workbenchof the thermal module. Then, the temperature distribution as thermal load imports modulestructure which the effects of the thermal deformation is analyzed through the temperaturedistribution of the ball screw.3, A thermal distribution and the deformation of hollow ball screw was deeply studiedunder different rotating speed and it is concluded that the relationship between therotational speed and the thermal deformation. At the same time, it is verified the validity ofthe simulation model by theoretical model. With the increase of the coolant flow rate,hollow ball screw’s temperature distribution and thermal deformation presents a trendweakening the influence of cooling fluid.4, The influence of the heat dissipation performance is analyzed by simulation indifferent kinds of cooling medium with hollow ball screw. The hole size is a main factorconsidering the strength and rigidity in the simulation of hollow ball screw. In order tostudy the hollow ball screw to reach thermal equilibrium time on numerical controlmachine hot start, the comparison of hollow/solid ball screw are studied in the simulation.5, The mathematical model of servo feed system is established, and M file is compiledin MATLAB/Simulink. It is verified hollow ball the stability of servo feed system by theBode Figure and the stability of system is proved By the Routh criterion. The rapidity ofhollow ball screw is better than the solid after the contrast of the inertia parameters of thehollow/solid ball screw in the servo feed system. 6, In view of the hollowing will affect the strength and stiffness of a ball screw. So,the checking is carried out for the strength and stiffness. The results meet the requirementsof strength and rigidity.This paper provides theoretical basis for the use of hollow ball screw in numericalcontrol machine tool servo feed system, which has important engineering practicalapplication value.