Research On Geometric Error Modeling And Compensation Of Five-Axis CNC Machine Tool

The machining accuracy of machine tool is mainly restricted by three aspects: the thermal error caused by deformation of machine tool’s mechanical components, the geometric error caused by manufacture, assembly and abrasion, and the stiffness error due to cutting. Under this background, the method of improving the accuracy of NC machining is studied in this paper from the angle of geometric error, which is one of the main reasons to improve the machining accuracy. Three parts contains geometric error modeling, parameter identification and error compensation are studied.The research object in this dissertation is the five-axis NC machine tool with BC dual turntable whose primary axis is B-axis and secondary axis is C-axis. In the aspect of geometric error modeling, the multi-body theory and the homogeneous coordinate transformation are utilized to represent the motion transformation in the kinematic chain. For each axis, both link error and motion error are under consideration. In the aspect of parameter identification, a new decoupling measuring strategy and identification algorithm are proposed for the link error and motion error. In particular, the detecting method of geometric error on rotary axis is designed on account of reference coordinate frame of machine tool and the coordinate frame fixed on the axis. The identification algorithms are deduced and for the methods based on simplified model are simulated. On the premise of the above work, an new off-line G-code modified error compensation algorithm namely the method of twice correction of the compensation code is proposed. Based on whether the twice correction compensation strategy is adopted, the multiple sets of contrast compensation experiments are carried out, and finally the effectiveness of the proposed compensation algorithm is verified.