Smoothing Method Of Tool Axis Vector For Curved Surface Five-Axis Machining Based On Kinematics

The rapid development of the aerospace industry has led to the widespread use of complex curved parts which meet the performance requirements of high-end equipment.However,the complex structure of the surface increases the difficulty of processing.The five-axis CNC machining with a flexible tool attitude is an effective means to achieve efficient machining of complex curved parts.Due to the complex profile characteristics,the tool axis vector between adjacent tool contacts during the machining process is abrupt,resulting in a sharp increase in the angular velocity and angular acceleration of the machine feed rotary axis,which seriously affects the stability of the machining process and causes the processing quality to decrease.Due to the complex profile characteristics,the tool axis vector between adjacent tool contacts during the machining process suddenly changes,resulting in a sharp increase in the angular velocity and angular acceleration of the rotary feed axis,which seriously affects the stability of the machining process and causes the processing quality to decrease.And the limitation of the axial movement ability,the actual feed rate will drop sharply due to the sudden change of the tool axis vector,and it is difficult to reach the command value,which affects the machining efficiency.At present,commercial CAM software often uses the methods of fixed tilt angle and yaw angle to generate the tool axis vector.In the process of machining complex curved parts,the conservative feed rate is adopted to meet the limitation of the motion ability of rotary axis,so the high quality and efficient machining of the parts cannot be realized.In summary,reasonable planning of the tool axis vector can not only make the rotary feed axis run smoothly during the surface machining process,but also has important significance for ensuring the machining quality of the parts.In view of this,this paper considers the kinematics constraints of the rotary feed axis of the machine tool to research the optimization method of the tool axis vector.The main contents are as follows:Firstly,the method of solving tool-path and calculating dynamic characteristics of machine tools are studied.By establishing the parametric surface equation and combining the residual height and the chord height error constraint,the tool-path spacing and the tool step length are solved,and the tool position file of the complex surface machining is obtained.According to the transformation relationship of the tool axis vector in different coordinate systems,the kinematics and inverse kinematics calculation model of the machine tool are derived.Based on this,the calculation formula of the kinematic parameters(the angular velocity and angular acceleration of the rotary feed axis)of the rotary feed axis of the machine tool is derived.Secondly,in order to reduce the kinematic parameters of the rotary feed axis of the machine tool,the local optimization method of the tool axis vector is researched,and the tool axis vectors in the optimization interval are optimized.The surface model is established in UG and the tool position files of surface machining are obtained.The angular velocity and angular acceleration curve of the rotary feed axis are simulated by MATLAB,and the vector angles of adjacent cutter contacts were calculated to select the optimization interval of the tool axis.Then,based on the quaternion method,the tool axis vectors in the optimization interval are optimized.In addition,interference check is performed on the optimized tool axis vector to avoid local or global interference between the machining tool and the curved workpiece.Finally,the actual test sample is machining to verify the validity and correctness of the proposed method.Finally,the global optimization method of the tool vector based on the minimum angular acceleration is researched.Based on the tool position file processed by UG,the feasible space of the tool axis vector at the cutter contact is calculated according to the principle of interference judgment.The key tool axis vectors are determined by judging the concave and convex curve of the tool-path curve.Then the tool-path curve is divided into sections,and the tool axis vector is optimized with the minimum angular acceleration as the target in each interval.On this basis,the tool axis vectors at the joint position of the adjacent interval segments are adjusted to ensure the tool axis vector smooth on the entire tool-path.Finally,by designing the experimental samples,the combination of simulation analysis and experimental verification is used to verify the effectiveness of the proposed tool axis vector optimization method to improve the surface quality.The tool axis vector optimization method proposed in this paper provides a reference for its futher research,and has certain engineering application value for the actual machining of complex curved surface parts.