Research On The Tool Orientation Optimization Under The Kinematic Constraints In Five-axis Machining

Five-axis machine tool is widely used to machine the complex parts in the aeroengine such as blisks.Five-axis machine tool has two extra rotaries and then it can make the process of manufacturing more flexible but it is also a challenge for controlling the tool orientation.The tool orientation is usually scheduled by the geometric shape of the tool and the part.But the tool orientations generated by only considering the geometric information may cause the dramatic change between two adjacent cutter locations.The dramatic change make the kinematic parameter of rotary exceed the kinematic capacities of the machine tool,deteriorate the efficiency and quality and even destroy the surface of the part.So,the smooth adjustment of tool orientation under the geometric constraints is important for the high-speed and high-precision demand in five-axis NC machining.In this thesis,a tool orientation optimization method for five-axis machining is proposed to smooth the tool orientation in five-axis NC machining under the collision-free and kinematic constraints,and the main research contents are as follows:(1)The initial tool orientations are transformed to coordinates of rotary axes and accessible coordinates of rotary axes are solved under constraints of workpiece surfaces.The coordinates of rotary axes corresponding to the initial tool orientation in the part coordinate system are firstly presented by using the inverse kinematics transformation.Meanwhile,a search model is established for directly finding the collision-free combinations of two rotaries by discretizing the strokes of two rotaries and then checking collision using the distance between the tool axis and the surface points of the part.(2)Based on the discrete tool path and accessible coordinates of rotary axes,tool orientation optimization linear programming model is established under constraints of kinematics.The optimization model aims at minimize the change between the initial rotary coordinates and optimal rotary coordinates by comprehensively considering the constraints of collision-free ranges and the kinematic constraints of angular velocity,angular acceleration and angular jerk for rotary axes.The tool orientation optimization model is transformed into a linear programming model by making a variable replacement for the optimal coordinates of the rotaries.The optimal tool orientation is obtained by solving the model and thentransforming the coordinates of two rotaries using the machine tool inverse kinematics transformation.(3)Machining simulation and the experiment of the blisk is performed to verify the effectiveness of the method we presented.The processing technic of blisks is researched and then the initial tool path of rough,semi-finish and finish machining is generated by UG software.The proposed tool orientation optimization is used for the tool path of blades finish machining.Machining simulation and the experiment of the blisk were conducted to validate the proposed method can improve the kinematics of the machine tool and obtain higher efficiency and better surface quality.