Study Of Machine Tool Axis’ Movement In High Feed Speed Surface Machining Based On The Redundant Degree Of Freedom

The aim of the mechanical processing is to be more effectively in the machining process, and one important way to get the target is to improve the feed speed. In the process of high feed speed machining, shock and vibration may occur due to the surface’s changing curvatures and the excessive speed of machine tool axis, which can affect the quality of the mechanical parts directly, even lead to the damage of machine tools’ internal structures.Aimed at the high feed speed surface machining technology, a method to improve the performance of each axis based on the redundant DOF (degree of freedom) is put forward in this thesis. The core method is to adjust the movement of each axis based on redundant DOF, considering the Kinematics and dynamics characteristic of each axis, by which the objectives of this thesis can be attained ultimately:to raise the feed speed in the case that machine motor is not overloaded, to improve the stability of each axis, to avoid the vibration and shock of machine tools, and to improve the surface quality of work-piece. This thesis mainly involves the following aspects:(1) Composition and decomposition of the machine tools’ movement under the redundant DOF. The transformation of machine tools’ movements is established to figure out the relationship between machine tool axis’ movement and actual processing path. The impact of redundant DOF on machine tool axes’ movements is analyzed, which can be regarded as the principle to adjust machine tool’movement. The nonlinear error with redundant DOF is calculated.(2) Analyses of machine tools’ kinematic and dynamic characteristics based on redundant DOF. According to the original data, the kinematic characteristics (including the feed speed, acceleration, and jerk) of the machine tools in the whole process can be obtained. The constraints of machine tool axes’ movements are inferred by analyzing the machine tools’servo motor drive and the characteristics of the servo drive system, which can be used as the principle to judge the rationality of each axis’ movement and to judge which axis is beyond constraint conditions.(3) Modification of machine tools’ movement with redundant DOF. The movement of overrun axis is modified according to the dynamic constraint of machine tools, and the other two axes’ movements can also be calculated based on the decomposition principle of machine tools’ movement, thereby the modification of each axis’ movement can be completed. By this method, the movements of every axis can satisfy the limitation of machine tools’dynamic constraint well, and can be more balanced, so as to reduce machine tools’vibration and shock, to improve the surface quality and to raise feeding speed;(4) Experiment of shoe last surface machining by five axis NC machine tools. Take the 5-axis machining of shoe last as an example, the displacement parameters of each axis front and rear modification are turned into NC programs, which can be used to manufacture the shoe lasts. After that, the processing effects machined with two different programs are compared to verify the validity of the modification method in this paper, which can make a contribution in improving the effectiveness of the machine tool’s stability and raising the feed speed.