Research On High Speed Smooth Tnansition Algorithm For Five-Axis Continous Small Line Segments

Five-axis CNC system has become an important means of complex thin-walled parts processing.The toolpath is the most important factor that influences the quality and efficiency of machine.It directly affects the life of machine and machine tools.Currently,the trajectory planning of five-axis CNC system mostly focus on geometry.In this article,it optimized the toolpath from three aspects:dynamics,kinematics,geometry.Firstly,it considered the influence of stiffness in terms of dynamics.The stiffness model of machine system and parts were established in order to calculate the stiffness matrix of machine system and the normal stiffness of parts.The results were used to adjust cutting parameters and compensate the contour error.Secondly,it considered the local smooth of continuous small line segments in terms of geometry.Using the Bézier curve to smooth the toolpath realized the G³ continuous at the corner of small line segments.Third,it considered speed constraints of the new toolpath by taking the error distribution model and the servo ability of each axis into account.Finally,it used the lookahead algorithm and combined with the S acceleration and deceleration strategy to realize the speed interpolation.The main research contents of this paper are as follows:Firstly,it deeply studied the Bézier curve,S acceleration and deceleration strategy and the lookahead algorithm and introduced some basic concepts in order to provide theoretical support for the research of following chapters.Secondly,at the beginning of the cutting toolpath planning,it considered the influence of stiffness in terms of dynamics.First of all,taking an example of the impeller blade,this article established a finite element method using the ANSYS to calculate the normal stiffness of impeller blade.According to the stiffness distribution,we can adjust the local cutting parameters.Then,it established the stiffness model of the machine system using the simplified three-dimensional model of the machine and compensated the contour error using the stiffness matrix.Thirdly,it studied the smooth of a two-dimensional toolpath which realized the corner smooth and G³ continuous using the rational Bézier transition pairs.At the same time,it also established an error distribution model in order to ensure that the Comprehensive trajectory error is less than the given accuracy.Then,in order to apply them to three-dimensional toolpath,it used one rational Bézier transition pairs to represent the trajectory of one point on tool tip and another to represent the trajectory of one point on tool axis.The Parameter synchronization also was considered.Then,using this algorithm smoothed the five-axis toolpath.Then,it considered speed constraint of the new toolpath by taking the error distribution model and the servo ability of each axis into account.Finally,it used the S acceleration and deceleration strategy and the lookahead algorithm to do the speed interpolation.