Testing And Analysis Of Frequency Response Characteristics For Multi-axis Machining System

Dynamic characteristics of multi-axis machining system play vital roles on surfacequality of the workpiece, the life of machine tool and cutting tools. The machining systemconsists of machine bed, axis of motion, spindle, tool holder, tool and workpiece. It can bedivided into two subsystems, which are tool subsystem and workpiece subsystem.Frequency Response Function (FRF) is broadly used to describe dynamic characteristicsof the machining system. Obviously, dynamic characteristics of tool subsystem andworkpiece subsystem have certain influences on dynamic characteristics of the entiremachining system.The main contents are as follows. Firstly, the relationship between machiningsystem’s general FRF and the two subsystems is deduced. Secondly, dynamic model of thetool subsystem is established. A novel response coupling method, which applies bothexperimental and finite element simulation to acquire FRFs of the tool point, is proposed.Uniform distributed spring and damper elements are used to simulate dynamiccharacteristics of the joint between tool and holder. Experiment and simulation is appliedto identify stiffness and damp coefficients of the joint between tool and holder. Thismethod can be carried to predict FRFs of varied combination of holder and tool. Thefeasibility of the tool subsystem’s dynamic model is verified by experiments. Then,dynamic model of the tool subsystem is established, considering the influence of theworkpiece’s clamp and rest on dynamic characteristics of the machining system. Theworkpiece finite element model is performed to predict FRFs at different location of theworkpiece. The accuracy of the workpiece subsystem’s dynamic model is verified throughexperiments. Finally, the proposed dynamic model of machining system is applied toanalyze the influence of tool length, tool diameter and tool posture on the tool point’sFRFs, and to predict the different position’s FRFs on the workpiece.In this thesis, dynamic characteristic of muti-axis machining system are investigated.experimental and finite element methods are combined to acquire the machining system’sgeneral frequency response function, which provided a basis for the optimization ofmachining parameters.