Research On Stiffness Of Milling Compound Spindle Box With Extensible Grinding Function

In recent years,with the rapid development of compound machining technology and compound function machine tools,various kinds of Lathe-milling compound machining centers,Lathe-grinding compound machining centers,Lathe-milling-grinding compound machining centers emerge in endlessly,their functions become more and more powerful,their configurations become more and more high-end,their machining precision and efficiency are also getting higher and higher,which greatly meets the needs of high-end market.But we are faced with a very realistic problem,that is,the high price,a large number of small and medium-sized customers with demand can not be expected.Therefore,the development of economical simple compound machine tool has been accelerated,that is,the general machine tool as the main body,through the basic function expansion,to meet its processing requirements.Therefore,new requirements for modules with functional expansion are put forward.In this paper,the dynamic and static stiffness of the spindle box of a NC milling lathe MC450 with expandable grinding function is studied.The main points are as follows:1.Static stiffness and modal finite element analysisThrough the modal analysis and static stiffness analysis by Ansys,on the one hand,the deformation nephogram,modal distribution and modal shapes of the whole machine are obtained,and the relationship between the spindle box components and the modal of the whole machine is clarified;on the other hand,the deformation law of the whole machine and the spindle box is obtained.2.Research on dynamic stiffness test and pretightening force control of spindle boxThrough the design and construction of dynamic stiffness test system,several spindle boxes of NC lathe are selected for dynamic stiffness test and spindle preload control test,and the test results are analyzed and studied.(1)The relationship between the axial and radial dynamic stiffness and the resonance frequency of the spindle box,and the influence of the coaxiality of the bearing mounting holes on the axial resonance frequency of the spindle box are studied.(2)Through the dynamic stiffness test and the least square fitting method,the influence of the fit clearance between the outer ring and the box on the axial resonance frequency of the spindle is studied,and the influence of the locking moment of the spindle bearing on the resonance frequency of the spindle is studied,and the deformation equation is established.(3)On the basis of the previous experimental data and analysis results,the dynamic stiffness evaluation and pre-tightening force control index of the spindle box components tested are preliminarily determined.The dynamic stiffness evaluation and pre-tightening force control index of the spindle box3.Static stiffness test of spindle box:The static stiffness test system is designed and built.Several spindle boxes of NC lathe are selected for static stiffness test,and the relationship between static stiffness and dynamic cutting performance is studied.(1)Through static stiffness test and analysis,the correlation between static and dynamic stiffness is studied.(2)The relationship between the theoretical value and the experimental value of the static stifness of the spindle bearing is studied,and the error analysis of the static stiffness experiment is carried out.(3)Study the relationship between axial static stiffness and axial resonance frequency of spindle box.(4)Study the relationship between radial stiffness and radial resonance frequency of spindle box.(5)The relationship between axial static stiffness and axial vibration of spindle box was studied by cutting test on several machines.(6)Finally,on the basis of the previous experimental data and analysis results,the evaluation and control standards of the axial static stiffness of the composite spindle box of MC450 milling car are established,and the realization approach is given.