Research On Recycling Of Machine Tool Parts Based On Stiffness Matching

With the rapid development of the global economy,the lack of resources and environmental pollution is becoming increasingly serious.As a key step in the recycling of used machine tools,redesign is essential to achieve energy saving and environmental protection.The five-axis gantry machining center as the research object,static and dynamic characteristics analysis of the machining center is carried out and weak parts are redesigned based on the finite element theory.The main contents are as follows:(1)The finite element model of the connecting plate is established.The accuracy of the model is verified by the modal test.The modal frequencies of the two connection plate structures are compared to select the structure suitable for the machining center.Then the finite element model of other parts of the machining center is established by using the same modeling method and its modal analysis is carried out.(2)The finite element model of machining center is established.According to the cutting force test,the static.analysis of the worst case of the machine is carried out,and the method with the coupling of rigid and flexible is employed to identify the weak parts of the machine X,Y and Z three directions.Then the whole machine is analyzed by modal analysis and harmonic response analysis.The results show that the Y stiffness of the column,the X and Z stiffness of the beam and the X and Y stiffness of the ram are lower,which is consistent with the results of statics.The stiffness matching design flow of the machine tool parts is proposed on this basis.(3)Machine tool parts redesign concept based on stiffness directivity is proposed.According to the modal shape,through the rational use of structural optimization design method,the natural frequency of the specific step mode of the structure is improved under maintaining the mass,so that the structure stiffness in a certain direction can be improved objectively.As the different structural parameters of the components of its direction stiffness sensitivity are different,①The column optimization is based on the change of the structure of the ribs layout.Three new column structure schemes are eventually formed.According to the analysis,the well shape structure is selected.The first and second order natural frequencies of the structure are increased by 40.3%and 8.8%,while the mass is reduced by 0.8%.The Y-direction stiffness of the column is improved.②The beam optimization is based on the size optimization of the structure.The weighted average of the first three natural frequencies of the beam under the free boundary condition is the largest under maintaining the mass.The X and Z stiffness of the beam are improved,and its first order nature frequency is increased from 148.76Hz to 160.82Hz.③The ram optimization is based on the change of the cross-sectional shape.The first three modes of modal frequency are increased under maintaining the mass.The X and Y stiffness of the ram are improved.The Optimized machine is analyzed by static and dynamic analysis.The results show the overall performance is improved under maintaining the mass.