Research And Design Of The FSW’s Spindle System Based On 3-TPT Parallel Robot

Friction stir welding(FSW)is widely used in the welding of light alloys as a new solid phase welding technology.Spindle system plays an important role in the weld shape and weld quality as a key component of friction stir welding equipment,not only to withstand the huge welding load,but also need to be able to adjust the process angle and forward inclination.3-TPT parallel robot has high rigidity,high load capacity,high precision and a series of advantages.Considering that there are no friction stir welding equipments in parallel in the market,a two-spindle spindle system is designed based on this,and transforms it into 5-DOF 3-TPT parallel friction stir welding equipment.The continuous welding duration and life is affected due to the load deformation and dynamic stability of the spindle system,the high temperature field of the spindle system which is Conducted by the high temperature generated by the stirring head.Therefore,the dynamic and static performance and thermal performance of friction stir welding spindle system are analyzed by means of finite element analysis and related steady state welding experiments.The main contents of this paper include:(1)The design requirements of the FSW’s spindle system is analyzed according to the structural characteristics of 3-TPT parallel robot and the requirements of 6xxx Aluminum Alloy welding load.The process parameters that affect the quality of the weld and the degrees of freedom required to weld all types of welds is summarized.(2)The three-dimensional model of two degrees of freedom FSW’s spindle system is established by solidworks.A/C-axis drive mechanisms are designedand and the parameter configuration of spindle bearings and spindle of the preliminary are designed.(3)The dynamic and static characteristics of the spindle are analyzed.The numerical simulation of FSW process is carried out and the curve of axial force is obtained according to the process parameters.The stiffness of the bearing is calculated according to the empirical formula,and the static stiffness of the spindle is analyzed by using Ansys.The dynamic model of the spindle is established by transfer matrix method,and the resonance frequency and critical speed of the spindle are solved.The relationship between natural frequency,bearing rigidity and supporting span is analyzed(4)The thermal characteristics of the spindle system are analyzed and the spindle system is improved.The heat generated by the stirring head and the heat generated by the spindle bearing are calculated respectively.The boundary conditions of heat dissipation of the spindle system are analyzed,and the convective heat transfer coefficients are calculated.The temperature field of spindle system is analyzed by Ansys.(5)The influence of the heat generated by the stirring head on the temperature field and the rotation accuracy of the spindle system is measured and verified by the welding experiment.Four types of stirring heads were designed and processed according to the design principle.The steady-state welding experiments are carried out by using the four types of stirring heads designed respectively.