A new contouring error estimation for the high form accuracy of a multi-axis CNC machine tool

Abstract

The evaluation of contouring error is important for multi-axis CNC machines because the tolerance specifications of manufactured parts are directly affected by contouring error. One of the fundamental quality inspections to verify that a manufactured part meets the expected tolerance is via form error evaluations. However, the existing estimation methods of contouring error are based on the position tolerance requirements. To meet the form tolerance requirements for the parts, this paper focuses on developing a high-accuracy estimation method of contouring error that is not related to a datum (ND-contouring error). In the proposed estimation method, at first, the minimum zone tolerance (MZT) method is used to transform the ideal tool tip path to match the actual one. Subsequently, by comparing the position and orientation between the actual point and the nearest point on the transformed ideal tool path, the ND-contouring error and orientation contouring error of the tool can be estimated, respectively. In addition, the difference between the proposed estimation method and previous evaluation methods is comparatively analyzed. Finally, simulations and experiments are conducted by applying the S-shaped and B-shaped machining trajectories, respectively, and the results all verify the estimation accuracy of the ND-contouring error estimation method. By adoption of compensation based on the ND-contouring error estimation, the contouring error could be significantly reduced, which will improve the quality of parts.