Research On Tool Posture Optimization And Singularity Avoidance Method For Five-axis Machining Of Complex Surface

China’s rapid economic development drives the take-off of manufacturing and heavy industry,and more free-form surface parts are applied to aerospace,shipbuilding and other industries.With the development of aerospace and shipbuilding,the machining requirements of free-form surface workpiece are becoming higher and higher,especially in terms of machining efficiency and machining accuracy.As one of the main machining technologies for machining complex curved surface parts,five axis NC machining technology has attracted more and more attention in the world.One of the core of five axis NC machining technology is the research of tool attitude angle in tool path.With the continuous improvement of computer software performance,more and more planning algorithms of tool attitude angle are proposed according to different machining requirements.At present,the design of tool axis vector in tool attitude angle is mainly to design a single tool axis vector based on the material removal rate,but there is a lack of research on adjacent tool axis vector groups,which leads to the failure to give full play to the advantages of tool attitude angle in five axis machining,and the planning algorithm of tool axis vector in tool attitude angle in specific singular phenomena is more complex at the same time.Considering the above practical problems,this paper studies the optimization technology of tool attitude angle in five axis machining tool path planning.The main research contents are summarized as follows:(1)The research on tool path planning and tool attitude angle for five axis machining is mainly based on the differential geometric information of complex surface workpiece.Therefore,the mathematical model of workpiece surface is established before tool path planning.The geometric information of workpiece surface includes the first and second basic quantities,the normal curvature of surface points,etc,The free-form surface workpiece is classified by extracting the geometric information of the workpiece surface.Based on the classification of free-form surfaces,the tool path is planned by using the residual height method of preliminary planning.On this basis,the tool local milling condition of tool attitude angle and the mathematical model of machining bandwidth and tool inclination are established.The tool axis vector in a single tool attitude angle is planned according to the machining efficiency.Then,for the trajectory with too large included angle of tool axis vector group,the included angle of adjacent tool axis vector groups is reduced by linear interpolation using quaternion method.,Finally,the preliminary planning of tool attitude angle is completed.(2)Aiming at the singularity problem in machining,firstly,the singularity phenomenon and the mechanism of singularity are analyzed.Through the analysis of singularity phenomenon,the singular region is calculated and the tool position data points are extracted;Then,according to the local milling condition of the tool attitude angle and the relationship between the machining bandwidth and the tool inclination angle,taking the tool contact as the adjustment center,the tool attitude angle is adjusted to avoid the singular region and meet the dual conditions of no overcut and the change of machining bandwidth;Finally,recursive interpolation is carried out for the tool axis attitude angle that does not meet the requirements of nonlinear error.Through the simulation data verification of the modified tool position data,the feasibility and practical value of the optimization algorithm proposed in this paper are finally obtained.