| In metal cutting,cutting force and chatter have always been the focus of attention.The dynamic change of cutting force may lead to the occurrence of chatter,resulting in the decrease of dynamic machining accuracy and surface quality of the machined parts and the increase of tool wear.In the current research on lathe chatter,it is usually assumed that the turning cutting force is linearly related to the dynamic cutting parameters,which is not in accurate agreement with the actual working conditions.Therefore,based on the analysis of nonlinear dynamic turning force,this paper studies the nonlinear chatter characteristics of lathe.The main research contents are as follows:(1)Based on the orthogonal cutting model,considering the dynamic cutting parameters,the dynamic cutting force model of CNC machine tools is established.In the cutting process,according to the force relationship and energy transformation between the tool and the chip during chip deformation,the static cutting force model is established based on the proportional relationship between cutting forces.Then the tool system is regarded as flexible,and the rest parts of the machine tool are regarded as rigid bodies.Considering the dynamic influence of tool chatter on cutting width and cutting thickness,a dynamic cutting parameter model is established.Finally,considering the unbalanced force caused by the error of machine tool spindle in the manufacturing and installation process,the dynamic cutting force model is established by combining the three.(2)Based on the regenerative turning flutter mechanism,a multi-degree-of-freedom turning flutter model is established.Firstly,the actual and transformed feed system parameters are identified according to Hooke’s law,hammer modal test and half power bandwidth method.Then the cutting force verification test and spindle eccentricity test are carried out,and the simulation cutting force is obtained by using the dynamic cutting force model and the flutter model.The correctness of the model is verified by comparing the two models.(3)Turning chatter test was carried out and the influence of each parameter on the dynamic characteristics of the system was analyzed.Firstly,the blade diagram is drawn according to the simulation results,and the turning flutter test is carried out.The test is compared with the simulation acceleration signal to verify the accuracy of the flutter model again.Finally,the influence of different cutting depths,different rotational speeds and different tool system stifness on the system dynamic characteristics is analyzed.The experimental verification shows that the dynamic turning force model and the proposed nonlinear chatter stability analysis method are effective,providing an effective method for accurately analyzing and characterizing the dynamic turning force and predicting and preventing the occurrence of turning chatter,and providing valuable theoretical support for improving the dynamic machining accuracy of the national CNC lathe. |
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