Life Prediction Modeling And Its Influence Analysis Of Ball Screw In CNC Machine

Ball screw pair is a common part in the transmission parts of CNC machining equipment.The transmission accuracy and performance of ball screw pair decrease continuously in the course of use,which eventually leads to various forms of failure of ball screw pair and the end of its service life.This kind of failure seriously affects the production quality and benefit of enterprises in the process of using NC machine tools.In order to prevent the failure of ball screw pair of CNC machine equipment,realize the ball screw more accurate prediction of service life has become an important problem facing the development of enterprises.In this paper,the ball screw pair of the feed shaft of CNC machine tool is taken as the research object,and the influence of process parameters on the life of ball screw pair is analyzed based on the definition of fatigue damage life of ball screw pair.A method for predicting and modeling the life of ball screw pair is proposed.By further theoretical deduction of fatigue damage life,the fatigue damage life formula can be more detailed and the service life of different cutting paths and cutting parameters can be predicted.The service life of different positions on the ball screw can be deduced.The main contents of this paper are as follows:(1)The failure modes of ball screw pairs are analyzed,the influence of process parameters on ball screw pair is discussed,and the service life prediction method of ball screw pair is put forward.The process parameters are divided into two parts: cutting parameters and processing path.The cutting force mechanics model under the influence of cutting parameters is analyzed,and the sectional life prediction model is established based on the processing path.The relationship model between process parameters and service life of ball screw pair is established through the stress analysis of bearing structure of machine tool screw pair.(2)The cutting force loading experiment of ball screw pair was carried out,and the life prediction model was improved.Based on the experimental platform of ball screw pair,the measured screw is loaded by the follow-up loading device in the experimental platform.The data acquisition software compiled by LabVIEW is used to collect the information of loading force and screw torque.The relationship between the three-way loading force and the axial load of ball screw pair is analyzed.The transfer relationship between cutting force and the axial load of ball screw pair is verified,and the life model is improved.(3)Using OPC technology of CNC machine tool,the data of feed axis from Siemens 840 D system are collected.Meanwhile,the cutting force information is collected by three-way dynamometer.The comparative experiments of different process parameters of the same part are carried out,and the service life of the established service life prediction model is analyzed.Thus,the feasibility of the service life model is verified by actual cutting experiments.(4)A single-objective optimization model considering the life of ball screw pair and a multiobjective optimization model considering the life and cutting efficiency of ball screw pair are established.Taking the spindle speed,feed speed and cutting depth as optimization variables,the optimization model is solved by genetic algorithm based on MATLAB platform.The results of optimization have a certain guiding effect on the selection of process parameters for technicians,and can meet the needs of Engineering applications.