Research On Five-Axis Cnc Machining Optimization Method Based On Performance Characteristics Of Machine Tool

High-end NC(numerical control)technology as a national strategic key field is technology blocked for a long time.Five-axis CNC machining technology is a typical high-end CNC technology widely used in aerospace,national defense,and other highend manufacturing fields.CAD/CAM system,NC system,and servo control system affect the quality and efficiency of 5-axis NC machining.But in the traditional NC machining process,the design of each system is relatively independent.When designing machining technology and NC system,it is necessary to consider the applicability of tool path and machine tool.Improving the applicability of tool path and machine tool can improve the machining efficiency and quality.In the CAM system,the design of clamping position and posture of parts is usually aimed at easy setup.But the influence of clamping position and posture on machine tool motion is ignored.In addition,the tool path is often expressed by small line instruction in 5-axis machining.However,the trajectory of small line segment is only G0 continuous,and the motion acceleration along the estimated motion is not continuous,which causes fluctuation of servo following error,machine tool vibration,and other problems.Therefore,it is of great significance to research the workpiece clamping position and tool path smoothing to improve the efficiency and surface quality of five-axis machining.The current workpiece clamping pose and tool path smoothness have the following main problems:(1)The clamping design does not consider the machine performance,resulting in machine singularity and low machining efficiency;(2)The effect of curvature fluctuation on machining quality is ignored,and only the geometric continuity between tracks is considered;(3)The method that smooth the tool location and tool axis trajectory respectively,and then establish the synchronous interpolation relationship between splines,requires more computing resources and affects the realtime performance of interpolation algorithm.This paper first proposes a machine tool applicability evaluation indicator based on performance utilization ratio,which comprehensively considers the balance of performance and utilization ratio of each moving axis of machine tool at each cutter location on the tool path.The indicator can be used to evaluate the applicability of a tool path to a specific machine tool.By analyzing the optimization method of performance utilization ratio,the technical roadmap of performance utilization ratio optimization is proposed: optimizing the workpiece clamping position and smoothing the NC system trajectory.The main research contents are as follows:To solve the problem of unbalanced utilization of machine tool performance,an optimization method of workpiece clamping position and pose based on performance utilization ratio was proposed.The machine tool singularities and workspace constraints were modeled in geometric space,and the clamping pose optimization model was established.It can effectively improve the balance of performance and utilization ratio,avoid singularity,improve the applicability of tool path and machine tool,and improve machining efficiency.To solve the problem of corner smoothing of tool point trajectory,a G2 continuous Dual-Bézier spline trajectory corner smoothing method considering the minimum curvature fluctuation was proposed.Firstly,the curvature monotone condition of the G2 continuous Bezier corner transition curve was deduced,and the construction method of symmetrical Dual-Bézier spline corner smooth spline was established,which optimized the performance utilization ratio of straight spines and improved the machining efficiency.Compared with the existing method,the performance utilization evaluation indicator is reduced,and the maximum curvature is reduced.To solve the problem of tool path smoothing in five-axis machining,the SMM(Space of Master-slave Movement)and a five-axis path smoothing method is proposed.The asymmetric Dual-Bezier spline model established the synchronization relationship between the rotation axis and the straight axis in SMM.Forward,the interpolation method in SMM is proposed.The tool path smoothing effects under different Angle errors were compared: When the Angle tolerance was increased by 10 times,the machine tool applicability indicator was reduced.Based on the above research,the clamping pose optimization prototype software and the tool path smoothing module were developed in the domestic CNC system.Experiments were carried out on the impeller blade and complex free-form workpiece in a table-tilting type machine tool.The results show that the smooth tool path can effectively improve the mechanical vibration of the impeller and improve the surface quality.The workpiece clamping position and pose optimization can improve the machining efficiency of the complex free-form workpiece,avoid the machine tool singularity and improve the surface quality.