Research On Temperature Characteristic Simulation Modeling Of Precision Linear Feed System

The processing accuracy of NC machine tools is constantly improving,and its thermal error is caused by uneven temperature distribution.The heat generation of linear feed system of NC machine tools mainly concentrates on ball screw unit and slider unit of guide rail.Their thermal deformation will directly affect the processing accuracy of NC machine tools.In this paper,the linear feed system of precision CNC machine tool was taken as the research object,and the finite element model of temperature field of ball screw unit and slider unit of guide rail was established,which provides the theoretical basis for the thermal stability optimization design of linear feed system.The main contents are as follows:1.Based on the theory of heat transfer,a theoretical model of heat generation and heat transfer of the main heat source of the precision linear feed system was established.Calculating the heat generating power of the main heat source of the linear feed system and the heat dissipation coefficient of the linear feed system provides load data for establishing the finite element model of the temperature field of the linear feed system.The calculation software of heat generation load/heat dissipation boundary condition was developed by using MATLAB.2.The finite element model of temperature field of ball screw unit and guide slider unit was established by coupling thermosetting and fluid module of finite element software.In the model,the reciprocating linear motion of ball-nut relative to screw and ball-slider relative to guide rail in actual operation,the thermal contact resistance between key contact surfaces and the heat transfer between cooling fluid flowing into the hollow screw and the inner wall of the screw were considered.The established finite element model can provide theoretical basis for the thermal stability optimization design of linear feed system.3.Based on the established finite element model of temperature field of linear feed system,the temperature characteristics of ball screw unit under different feed speed,different cooling fluid temperature and different cooling fluid flow rate,and the temperature characteristics of slider unit of guide rail under different feed speed,load and ambient temperature were studied.It provides a theoretical basis for the cooling strategy and operation selection of CNC machine tools.4.The temperature characteristic test of the linear feed system was designed and carried out.The temperature data of the key points in the nuts measured under different cooling liquid temperature conditions were compared with the temperature data calculated by the finite element method.The accuracy and reliability of the finite element model were verified.The finite element model of temperature field established in this paper takes into account the effect of reciprocating relative motion of ball screw nut pair and slider pair and the heat transfer relationship between key contact surfaces.The accuracy of the finite element model is higher.Based on the established finite element model,the temperature characteristics of the linear feed system under different operating conditions are analyzed,which has a certain reference significance for the selection of operating conditions of the linear feed system.