Matching Design Of Static Stiffness Of Feed System Of NC Machine Tool

Ball screw feed drive system is widely used for transmission in modern precision machine tool.Under the action of load,contact deformation will occur due to the existence of static stiffness,directly affects the machining accuracy.In the design stage,based on the stiffness design requirements,determining the component stiffness of feed system through stiffness matching can provide theoretical basis for machine tool design and greatly improve design efficiency and reliability.Therefore,taking a NC machine tool as research object,the modeling and matching design of feed system stiffness are researched.The main research contents are as follows:The axial stiffness model of feed system and coupling stiffness model between feed systems are established.The axial stiffness of components is deduced,and the axial stiffness model of feed system is established according to the axial fixation modes of the lead screw.Based on the differential vector error modeling method,coupling deformation model between feed systems is established.After defining components stiffness coefficients,force analysis are performed,then relationships between component deformation and stiffness are built.Based on mapping between force and deformation,coupling stiffness model between feed systems is established.The stiffness matching design is performed based on multi-objective linear programming.The stiffness coefficients ranges of functional components are obtained by referring the sample manuals and performing experimental measurement.Then four stiffness coefficients influenceing mostly on coupled stiffness are selected as target variations through sensitivity analysis.Combining with coupling stiffness design requirements,the stiffness matching result of each component is obtained by executing multi-objective linear programming in the MATLAB.Finite element simulation is carried out to verify the correctness of the stiffness matching results.The simulation model is established in ANSYS and verified by a case of machine tool.Substituting the stiffness matching value into the finite element model,the whole machine stiffness is simulated.Compared with the stiffness design requirements,the matching design results of static stiffness are verified.Experiments are performed to verify the stiffness models.The axial stiffness of the feed system and coupling stiffness between feed systems are measured by using the self-designed static stiffness measuring device.Comparative analysis shows that the experimental results are in good agreement with the theoretical results,which proves that the established stiffness model is reliable.