Research On Double-cutter And Double-surface Machining Technology Based On XYZ-3RPS Serial-parallel Mechanism

These years, the level of CNC technology at home and abroad has been significantly improved. However, some defects, such as repeated clamping,machining-vibration and low processing efficiency, still exist in current machining process. In order to solve these above problems, a method based on double-cutter and double-surface machining technology of serial-parallel mechanism tool was introduced in the text. Namely, two sets of the same serial-parallel device was arranged symmetrically to realize the double-cutter and double-surface machining processes of both symmetrical workpiece and non-symmetrical workpiece. This technique can effectively improve working efficiency and surface quality of free-form surface parts.The analysis of the structure features and kinematics of six-axis horizontal type serial-parallel machine tool were made in the thesis. The key component of double-cutter and double-surface processing unit is serial-parallel mechanism, which was designed according to the demand that can make the 3RPS parallel mechanism to be installed on the X axis end effector of 3 degree of freedom series mechanism. Firstly, parameter decoupling was done for 3RPS parallel mechanism with few degree of freedoms, thereby obtaining the independent parameters of this spatial mechanism. Then, analytical method, iterative method and vector method were employed respectively to establish the inverse solution model, forward solution model and speed & acceleration model. At last, kinematic simulation for serial-parallel mechanism was done based on the software of MATLAB and ADAMS to provide basic theories for CNC system and double-cutter and double-surface machining.According to the structure features of serial-parallel processing device, modular programming was used to develop the NC system cater to this serial-parallel device. Five basic functions(machine tool reset,locating workpiece coordinate,post-processing,kinematic control and process monitoring) of NC system of serial-parallel device were analyzed and simple algorithms which can achieve the corresponding functions were introduced. The control system cater to this device was developed with the help of VC++, in accordance with the existing feature(three-decker) of open CNC system.In order to achieve the function of double-cutter and double-surface machining process, a double-cutter path planning method, based on section method and projection method, was introduced. In the light of the features of double-cutter and double-surface machining process, the reconstituted B-spline curves and surfaces was further discussed. Simultaneously, cutter contact tool path of machined surface was obtained using section method and cutter location data was scattered via projection method. The collision of free tools and following cutter was avoided through laying collision avoidance plane. Follow processing of interference region was achieved by means of avoiding distance. Finally, bar length of double-cutter and double-surface device was gained with the help of the reversely obtained cutter location data. The validity and effectiveness of double cutter position planning were proved via the simulations on the ADAMS platform.Processing and simulations of serial-parallel device and double-cutter and double-surface machining mentioned in this thesis were done respectively. The Processing and simulations of blade surface and spherical surface of propeller proves the feasibility of processing freeform surface parts of serial-parallel mechanism. The simulations on the MATLAB and ADAMS proves the feasibility and effectiveness of using “section method” and the “projection method” to scatter cutter location data. Thus, to achieve double-cutter and double-surface machining is for available and it also proves that this combined method can dramatically improves the working efficiency of freeform surface parts’ s processing.