Study On Geometric Error Tracing For Five-axis Machine Tool Based On DBB

This dissertation deals with the key issues relevant to error modeling,error measurement and error identification of a five-axis CNC machine tool.The following achievements have been obtained.According to the structure of the machine tool,the error elements of prismatic pair and revolute pair are analyzed and the geometric errors of the machine tool are obtained.Based on the homogeneous coordinate transformation principle,the transformation matrixes of tool kinematic chain and workpiece kinematic chain are established.Also,the transformation matrixes of tool coordinate system with respect to workpiece coordinate system are obtained,then the geometric error model is established as per small angle assumption.The polynomial expressions of translational axes errors are established based upon the double ball bar(DBB),and the error identification model of three translational axes can be obtained.Aiming at the two rotational axes,different installation methods of DBB are designed in radial,tangential and axial direction and mathematical models are established to identify the geometric errors.Thus,the error identification model of machine tool is obtained.On the basis of above work,experiment is performed by DBB in different measuring patterns.According to the experimental data,the main geometric errors are identified,which shows the effectiveness of the proposed method.The above achievements lay foundation for the error tracing and error compensation.