Research On Five-axis Machining Feedrate Planning And Nonlinear Error Control Methods

In recent years,five-axis NC machining technology in China and the world has been rapidly developed.This advanced manufacturing technology is widely used in various related fields of modern manufacturing,such as aerospace precision impeller processing,military defense,mold manufacturing and so on.Five-axis NC machining is the pursuit of speed,high precision,in order to achieve this goal,in the study of fiveaxis NC system mainly from the following aspects: tool path planning,tool path interpolation,feed speed control,post-processing development and servo control system research and development.In order to improve the speed and accuracy of the research tool path interpolation algorithm and feed speed planning control research has become the most important.(1)A new method of feed rate planning and control is proposed to solve the problems of difficult prediction of deceleration point in five-axis interpolation and overlimit of rotation axis angular velocity/angular acceleration caused by translational axis velocity planning.The method is based on the constraint of the axis of rotation angular velocity/angular acceleration control,and the calculated actual translational axis up to speed/acceleration translational axis speed of the reentry after planning,deceleration control law based on translational axis acceleration,uniform speed and deceleration stage are calculated respectively,the number of interpolation cycle and residual distance will be evenly distributed to each decelerate at the end of the cycle in order to make the last cycle just arrived at the end point of section interpolation path.The results show that the proposed method can accurately locate the end point of the interpolation path segment without predicting the deceleration point,and that the rotation axis and the translational axis can coordinate the acceleration and deceleration process under their respective kinematic constraints,which has a good practical value in improving the performance of machine tools and motion control accuracy.(2)The kinematics of the five-axis CNC machine tool was solved in detail,and the reasons for the nonlinear error of the five-axis CNC machine tool in the position of the tool tip during machining were analyzed,and the mathematical model of the nonlinear error was established according to the kinematics transformation and the geometric relationship between the tool and the processed workpiece.By the method of homogeneous coordinate transformation,the mathematical expression and inverse calculation formula of the actual position of the tool tip during machining are derived.Aiming at the nonlinear error caused by the rotation axis movement of a five-axis nc machine tool,a method of inverse interpolation compensation is proposed.From the Angle of five-axis nc machining rotating center interpolation algorithm,the nonlinear error reduction method is considered,and the position of rotating center interpolation is solved by the position of the theoretical tip,so that the actual tip points are more likely to fall on the theoretical interpolation path.Simulation results with MATLAB show that the proposed method can effectively control the nonlinear error within the machining tolerance and significantly improve the trajectory control accuracy of the five-axis nc system.It can be seen that the method proposed in this paper has better feasibility and practical application value.