Research On Five-axis Machine Tool With Opposed Orthogonal Rotary Axis And Its Key Technologies For Machining Impeller And Blisk

Aeroengine is known as the "heart" of aviation industry.Impeller disc is the core part of aero-engine.Its processing efficiency restricts the processing cost,and the machining accuracy has a significant impact on the performance of the engine.At present,five axis machining center is generally used for impeller bladed disk.Due to the thin inlet and outlet gas edge of the blade and large variation of blade bending and twisting rate,the machining movement of the machine tool needs frequent acceleration and deceleration.Therefore,it is necessary to configure a rotating shaft with high dynamic response characteristics to meet the pose change requirements of the relative motion between the cutter and the surface.In view of the fact that the machining of aeroengine impeller blisk depends on the high motion performance of rotary axis,the relative displacement is reduced by the way of opposite rotation of cutter and curved surface parts,so as to obtain higher relative motion angular velocity and angular acceleration margin.A new five axis linkage machine tool structure is proposed,which adopts the method of orthogonal rotation axis opposite to realize the independence of rotary axis height High performance five axis linkage machining with motion characteristics,compact machine structure and high stroke utilization rate.A series of key technologies,such as structural design and optimization,kinematics analysis and solution selection,machining process programming and so on,are deeply studied.The new structure machine tool is realized from the external structure balance to the internal motion shaft load balance,and is applied in impeller milling.The specific research contents are as follows:In order to solve the problem that the curvature of the parts changes greatly when machining impeller bladed disk with three translational and two rotating structures,a new symmetrical parallel rotating shaft structure is proposed to realize the rotation motion of multiple rotating shafts and reduce the motion increment of a single rotary axis.Based on the design idea,combined with the milling application scenarios,a five axis linkage opposed orthogonal rotary axis machine tool structure scheme for blade milling is proposed.The static stiffness of the machine tool with symmetrical parallel rotating axis structure is analyzed by finite element method.Aiming at the weak component z-axis of machine tool static stiffness,an improvement strategy of translational shaft with better stiffness,compact structure and centroid drive is designed to effectively improve the static stiffness of z-axis.Through comparative analysis,the improvement effect is verified and meets the requirements of impeller machining.In view of the fact that the traditional decoupling method of rotation degree of freedom is not suitable for the inverse kinematics equation of three translational two rotary machine tools,a translation degree of freedom priority decoupling algorithm is proposed,and the closed form function model of inverse kinematics of machine tool is established.The relationship between multiple solutions of inverse kinematics and trajectory continuity is deeply analyzed,and a solution selection method for motion chain of 5-axis machine tool is proposed.On this basis,the virtual equal step interpolation method is used to analyze the single axis kinematics characteristics of the traditional machine tool and the new structure machine tool for the same impeller machining track,and the applicability of the five axis linkage opposed orthogonal rotary axis machine tool to the impeller parts is demonstrated.In order to solve the problem that the curvature of the tool axis changes too much,which leads to the imbalance of machine tool axis load during the machining process,a global tool attitude optimization model of machine tool axis load increment balance is proposed,and the tool axis is optimized by particle swarm optimization algorithm.Taking an aviation blade as an example,the paper analyzes the spiral path at the front and rear edges of the blade features,optimizes the front and rear paths,analyzes the motion performance of the two paths on the five axis linkage orthogonal rotary axis machine tool by using the virtual equal step size analysis method,and obtains the absolute velocity curve of each rotary axis of the machine tool.The results show that the optimized path can effectively balance the machine Load increment of each rotary axis of the bed.Based on the above research,the prototype of five axis machine tool with opposite orthogonal rotation axis is developed,and the prototype system of special machining programming software is developed.The correctness and feasibility of the motion decoupling method and related multi axis machining programming algorithm of a translational multi rotation axis machine tool are verified by designing and machining a certain type of aero-engine impeller.