| The demands for precision,dynamic stability and thermal stability of machine tools or equipments are growing by modern manufacturing industry,but it is getting more difficult for the traditional cast irons to meet these demands.In this case,composite material,as a new kind of material,has great potential to replace cast iron as a common material for machine tool structural parts because of its light weight,high damping and good heat dissipation.In this paper,different composite materials will be used to improve and optimize the bed,column and worktable in the machining center,and the dynamic characteristics of the whole machine will be optimized based on the mass matching method to improve the overall performance of the machine tool.The specific research contents are as follows:Firstly,taking the bed of HMC630 horizontal machining center as the research object,the composite structure based on "sandwich" is used to improve and optimize its design,the key design variables are extracted and the integrated framework of CAD/CAE is built.The response value of the test sample point is calculated and the response surface model is established.Based on this,the iSIGHT software integrated Matlab plug-in is used to build a multi-objective optimization framework to complete multi-objective optimization of composite structure bed mass,deformation,low-order natural frequency and cost,The thermal characteristics of the optimized bed structure are further analyzed to study its thermal stability.Secondly,in view of the low stiffness of the interface between the outer steel plate and the inner concrete of the composite structure bed,the stud connector is designed.Based on the analysis of the stress mechanism of the single stud connector and the differential relationship among shear force,bending moment and load concentration,a mechanical model of the shear stiffness of the single stud connector is established.Then,the key factors affecting the shear stiffness of single stud are further analyzed.Based on this,the change of the average shear stiffness of each stud under group nail effect and the influence of the number and spacing of studs on group nail effect are studied,which provides a theoretical basis for the design of connecting parts between inner and outer layers of sandwich composite structureThen,for the light weight and high strength requirements of the moving parts of the machine tool,the improved honeycomb-like structure is adopted to design the moving parts of the column and the table.Firstly,in order to improve the coplanarbearing capacity of traditional hexagonal honeycomb materials,a non-uniform thickness protective wall is constructed outside the hexagonal honeycomb cell structure to form a honeycomb-like cell structure,which is verified by equivalent elastic modulus calculation and finite element simulation.Then,through the analysis of static and dynamic performance of finite element method and heat dissipation performance,it shows that the improved filling structure can reduce the mass of structural parts and improve heat dissipation on the basis of ensuring static and dynamic characteristics.Finally,based on the mass matching method,the influence of different structural mass on the dynamic characteristics of the whole machine is studied.The response surface model between the mass of each structural component and the first three natural frequencies of the whole machine is constructed.When the mass of each structure changes at the same time,the key influencing factors are identified by sensitivity analysis,and multi-objective optimization is completed based on iSIGHT platform.The optimal distribution scheme of bed mass,column mass and table mass is obtained when the dynamic performance of the whole machine is optimal. |
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