Geometric error measurement and identification for rotational axes of a five-axis CNC machine tool

Abstract

It is difficult to measure the attitude errors of five-axis machine tools, as it requires expensive instruments. Furthermore, it is hard to measure and identify them at production sites. In this paper, the B/C type of five-axis CNC machine tool is studied; the rotational axes are in the cutting tool movement chain and workpiece movement chain. The method of geometric error measurement and identification of the rotational axes is proposed based on the use of a double ball bar (DBB). The geometric error sources in two rotational axes are analysed. Then, based on the homogeneous coordinate transformation principle, the relationships between the geometric errors of each rotational axis and the structure parameters of the machine tool are established on the C turntable and B swinging head, respectively. Identification models for each axis are built by changing the installation modes of the DBB in three coordinate directions. The geometric errors in the rotational axes are identified by the least-squares method. Finally, the error measurement experiment of the machine tool is carried out for different installation modes of a DBB. The experimental results show that the identified error parameters are consistent with actual conditions and verify the validity and feasibility of the proposed method.