Stiffness Matching And Dynamic Properties Analysis For The Ball Screw Feed Drive System

As a major component of a modern NC machine tool, the performances of theball screw feed drive system affect the positioning accuracy and the manufacturingquality of the workpiece directly. The stiffness and dynamic properties of the systeminfluence positioning accuracy and cutting stability a lot, so the research on stiffnessmatching and dynamic analysis of the ball screw drive has a high application value.Four aspects on the ball screw feed drive system are studied in the dissertation:stiffness matching method on the ball screw drive, finite element modeling andsimulation, electromechanical-coupled dynamics modeling and static stiffnessexperimental research. The main works and contributions are as follows:(1) The static stiffness model of the ball screw feed drive system is established basedon Hertz contact theory and basic principle of mechanics considering that therelation of each stiffness value is in series. Through simulation calculation, theeffects of geometry parameters, pre-load and the way bearings support the ballscrew on the static stiffness of ball screw drive are obtained. Considering the realcases, the basic principle of stiffness matching of the ball srew feed drive systemis obtained; considering the guide rail and slide interface stiffness, the workpiecedeformations model under static force are derived. The span of guide rails has aneffect on the deformations.(2) The finite element model (FEM) of a machine center’s feed drive system in Z axisis established with joint parameters added in based on SAMCEF. By modal andharmonic response analysis, the influences of the material properties of theworktable, diameter of the ball screw and joint parameters on the naturalfrequency of axial vibration are derived.(3) The electromechanical-coupled dynamics model of the feed drive system isestablished by taking the nonlinear friction and the non-constant stiffness alongball screw axis into consideration based on basic kinetic theory. The model ismore similar to the real physics model than traditional ones. By analyzing themodel with SIMULINK, the influences of mechanical and servo parameters onthe dynamic response are derived.(4) By using a dynamometer, dial indicator, loading device and other assistive tools, a method for measuring the static stiffness of the feed drive system is achieved. Bycontrasting the static stiffness experimental values of the feed drive system in Yaxis of a machine center in different positions with theoretical values, the staticstiffness model is proved right.