| The dynamic stiffness performance of CNC machine tools and the thermal error of the spindle system severely restrict the machining accuracy of the machine tools.However,dynamic performance is currently limited to the research and optimization of a single dynamic characteristic.At the same time,the established model is not accurate enough,which affects the optimization result.The digital twin of CNC machine tools should be able to predict dynamic performance and provide optimization solutions.However,the current concept of digital twins in the field of CNC machine tools has problems such as high-fidelity modeling and simulation,high-confidence simulation prediction,and providing effective intelligent optimization solutions,which need to be solved urgently.The dynamic characteristics of the whole CNC machine tools are studied in this paper,and the construction of the digital twin model of the dynamic characteristics,the modeling of the precise finite element model of the whole machine's dynamic stiffness,and the analysis of the whole machine's thermal characteristics are studied.At the same time,the dynamic stiffness and thermal deformation of the CNC machine tools are optimized to reduce the vibration and thermal deformation of the machine tools so as to meet the requirements of machining accuracy.The main research work and results of this paper are as follows:(1)In order to reflect the real situation in the whole life cycle of the machine tools,an adaptive modification method of the digital twin model of CNC machine tools coordinately driven by the mechanism model and the data model is proposed.The construction of the initial digital twin mechanism model and initial data model is achieved based on the dynamic stiffness of the whole CNC machine tools.(2)At different stages of the CNC machine tools' life cycle,intelligent optimization algorithms can be used to adaptively modify the digital twin model according to changes in the dynamic performance of its physical counterpart.And the established digital twin model can be used to predict the dynamic performance of CNC machine tools,which lay a foundation for the optimization of the dynamic performance of CNC machine tools.(3)The finite element method is used to carry out static analysis and modal analysis on the whole lathe machine,and the machine tools' modal test is carried out to verify the validity of the finite element model.The results of static analysis and modal analysis are considered comprehensively,and it suggests that the lathe machine needs to be optimally designed to improve the static and dynamic characteristics.(4)The topological optimization of the CNC lathe machine's bed is carried out.According to the results of static topology and modal topology optimization,the CNC lathe machine's bed is redesigned,and then the static and dynamic characteristics of the redesigned lathe machine are analyzed.After the redesign,the total static flexibility of the lathe machine is reduced by 2.55%,the first-order natural frequency is increased by 2.1%,the first-order dynamic stiffness is increased by4.8%,and the mass of the bed is reduced by 1.6%.(5)The thermal characteristics of the spindle system are analyzed,and the temperature rise test results show that the steady-state thermal analysis is reliable.The steady-state thermal analysis shows that the maximum temperature of the spindle system is 68.9 ?,and the maximum thermal deformation is 220.2 ?m.The maximum temperature and maximum thermal deformation of the spindle system are reduced by optimizing the structure of the spindle case and rearranging the heat source.After the optimization,the maximum temperature of the spindle system decreased from68.9 °C to 62.4 °C,a decrease of 9.4%,and the maximum thermal deformation decreased from 220.2?m to 176.3 ?m,a decrease of 19.9%,which proved the effectiveness of the optimization method. |
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