Research On Post-processing Technology Of Six-axis Ultrasonic Machining For Honeycomb Core Complex Curved Surface

Honeycomb core composite is a new type of composite material with high specific strength,shock absorption,fatigue resistance and so on,has been widely used in aerospace,automotive,ship and other fields.With the higher and higher precision requirements of honeycomb core structures in this field,higher requirements are put forward for the high quality and efficient machining of honeycomb core composites.Due to the traditional high-speed milling honeycomb core structure often has burr and dust pollution and other defects,and ultrasonic cutting technology as an advanced technology to achieve high quality and efficient machining of honeycomb core composites can improve the above defects.In the actual machining,the six-axis ultrasonic cutting machine is usually used to process the complex curved surface of the honeycomb core,but the commercial CAM software can not realize the post-processing of the six-axis NC program.Therefore,in this study,according to the special material properties and machining methods of honeycomb core composite materials,the airfoil complex curved surface composed of typical honeycomb core structural members is taken as an example to study the post-processing technology of six-axis NC machining.The main research contents and results of this study are as follows:(1)The motion mode of the NC machining of the complex curved surface of the honeycomb core was analyzed,the kinematics of the six-axis CNC machine tool was planned,and the structure and motion form of the six-axis five-linkage machine tool were analyzed.Combined with the kinematic chain relationship of the machine tool and the homogeneous transformation matrix,the kinematic modeling of the machine tool was carried out,and the relationship between the motion axis variables of the machine tool was established.On this basis,the sixth axis variable controlled by the servo spindle of the machine tool was analyzed emphatically,and the kinematics modeling of the straight-edged knife six-axis linkage machine tool and the solution of each axis variable were realized.(2)The virtual model of six-axis NC machine tool was constructed by Vericut,and the kinematics models of six-axis five-linkage machine tool and six-axis linkage machine tool were simulated and verified by circular interpolation and linear interpolation on plane,slope and curved surface,respectively,the approximate consistency of cutting state and error after simulation proved the accuracy of post-processing kinematics model and NC machine tool construction.Based on this,the verification of the machining process of straight-edged knife and disc knife for complex curved surface of honeycomb core is successfully realized.(3)Combined with the multi-body system theory and the homogeneous transformation matrix,the geometric error analysis and modeling of each moving axis and rotation axis of the six-axis five-linkage machine tool were carried out,and the total geometric error transformation matrix was established.The geometric error was compensated by NC code compensation method,and the NC instruction before and after correction was simulated and compared by machine tool.Under the maximum geometric error allowable value parameter,the error range of the sampling section is reduced by nearly 93%.(4)In this study,the nonlinear error caused by the inconsistency between the linear interpolation motion of the NC system and the nonlinear motion of the rotating axis in six-axis five-linkage NC machining was analyzed and modeled,the location of the maximum value of nonlinear error was analyzed,and the sinusoidal function method was proposed to optimize the error model,analysis of the main influencing factors of nonlinear error by theory and simulation.The adaptive linearization method was used to control the nonlinear error,and the new tool location file after geometric error control was sampled,the simulation results show that the average error in the sampling section after control is reduced by nearly 74.09%.Based on the above research results,a set of post-processing error compensation system for NC machining was established,the post-processing kinematics algorithm,geometric error compensation and nonlinear error compensation module were integrated into one whole,efficient and rapid realization of NC code conversion and error compensation,it has become an important means to assist the post-processing of six-axis NC machining.