Research On Structural Design And Optimization Of End-effector For Multi-function Milling

With the rapid development of material science and aviation industry,the application of Carbon Fibre Reinforced Plastics（CFRP）and titanium alloy is more and more widely,which not only brings the rapid development of equipment performance,but also presents new challenges to the hole making technology.As a new type of hole making technology,helical milling and inclined planetary milling can effectively improve the quality of hole making and tool life.In order to achieve high quality and efficient hole making of CFRP/titanium alloy laminates,an end-effector with helical milling and inclined planetary milling functions was designed in this paper.The mechanical properties of end-effector were studied.The main contents of the research include the following aspects:Firstly,the mechanical structure of multi-function milling end-effector is designed.The front and back two pairs of eccentric sleeves are determined as the spindle mechanism of functional realization structure.The cutting force model of carbon fiber helical milling is established and the force analysis of end-effector joint bearing was carried out.The key moving parts of the end-effector are selected and calculated according to the machining conditions.Secondly,the static model of the joint surface of linear guideway and rolling bearing in the end-effector is established.Based on Hertz contact mechanics and fractal theory,the analytical solution model of virtual material physical parameters of linear guideway joints is established.On this basis,the virtual material model of linear guideway joints surface and spring-damping model of rolling bearing joints surface are analyzed by finite element method.The first six modes,natural frequencies and dynamic stiffness characteristics of the two joints were obtained.Thirdly,the finite element simulation of the end-effector is carried out.The virtual material model of the linear guideway joint surface,the spring-damping model of the bearing joint surface and the rest of the end-effector are assembled.The finite element simulation model of the whole end-effector is established.The static and dynamic performance parameters of the whole end-effector are obtained,which provide data support for the subsequent improvement of the structure.Finally,in order to improve the end-effector stiffness and reduce weight,the optimization of end-effector frame structure is carried out.Based on the variable density method of topology optimization,the frame structure was optimized under three working conditions with the goal of maximizing the frame stiffness and weight reduction ratio as constraint,and the optimized assembly model of the frame is obtained.The performance analysis of the frame optimized assembly model is carried out,and the results show that the overall stiffness of the end-effector frame still meets the requirements under the condition of 34% mass reduction.