Research On The Aerodynamics And Dynamic Performance Of The Fly-cutting Machine Tool

In the inertial confinement fusion device,the KH2PO4(Potassium dihydrogen phosphate,KDP)crystal for frequency conversion requires high machined surface quality.Hence,a strict performance requirement of ultra-precision machine tool for KDP crystal machining is highly demanded.The vibration of the machine tool will directly affect the machined surface topography.The previous researches considered that the vibration of the machine tool mainly results from the vibration of tool tip excited by cutting force.However,since the machining is intermitted,the spindle speed is very high and the distance between the tool holder and the workpiece is small,there will be normal aerodynamic forces below the tool holder and on the workpiece under the influence of external air during the manufacturing process.Actually the aerodynamic forces directly result in the vibration of the machine tool and further affect the surface topography of the workpiece.This thesis mainly focus on the external aerodynamic forces and the dynamic performance of the fly-cutting machine tool,which provides theoretical basis for uncovering the formation mechanism of machined surface topography.Firstly,based on the structure of vertical ultra-precision fly-cutting machine tool,a simulation model for calculating the aerodynamic forces is built.The method of computational fluid dynamics(CFD)and finite volume are adopted to study the external aerodynamic forces on the slide and below the tool holder.The aerodynamic forces under different spindle speeds and machining positions in feed direction are analyzed to contrast the effect of spindle speed and machining position on the aerodynamic forces.Secondly,a simulation model of aerostatic bearing is built to study the stiffness of the spindle.According to the calculation results,the dynamic model of the machine tool is established by the spring equivalent method.Modal test of the machine tool spindle is carried out to verify the finite element model.On this basis,the vibration of the tool tip is studied by applying the cutting force and the aerodynamic force on the model.Besides,two results of tool tip vibrations are also calculated by exerting these two forces on the dynamic model of machine tool respectively.The impact of the aerodynamic force on the machine tool vibration is discussed by comparing these three vibrations.Besides,the vibration of the cutting point on the workpiece is studied by loading the cutting force on the model position of the slide corresponding to the machining path.Thirdly,an experimental device is designed and constructed to measure the aerodynamic forces on the workpiece.The influence of spindle speed on the aerodynamic force is studied by measuring and analyzing the forces on the workpiece with different spindle speeds.The aerodynamic forces are also measured and researched under different distances from the tool holder to the workpiece.In order to verify the correctness of the simulation model,the aerodynamic forces on the workpiece are calculated and compared with the experimental results.Finally,According to the research method in the vertical machine tool,the external aerodynamic forces and the stiffness of the spindle bearing of the horizontal machine tool are studied.On the basis of that,the dynamic model of the spindle system is established to research the vibration of the tool tip under the excitation of the cutting force and aerodynamic force.Besides,the impact of the aerodynamic forces on horizontal flycutting machine tool vibration is discussed.