Kinematic modeling and machining precision analysis of multi-axis CNC machine tools based on screw theory

This paper presents the solution to evaluate and predict machining precision of a multi-axis computer numerical control (CNC) machine tool. The "function-motion-action" method is used to describe the motion relationships of a multi-axis CNC machine tool, and the multi-body system structure model of the machining system is further constructed. By analyzing the motion process of the machine tool based on the meta-action layer and considering the motion transfer relations in meta-action chains, the kinematic models of each motion shaft are established in twist exponential form. According to the structural and kinematic relationships of these motion shafts, the kinematic and kinematic error models of the machine tool can be easily obtained. Then, the distance error formula is used to deduce the general model of machining allowance error. A simulation test and practical experiment are performed on a type of CNC controlled 5-axis machining center. The experiment results show that the proposed method is universal, and it can greatly simplify the kinematic analysis of multi-axis CNC machine tools. (C) 2019 Elsevier Ltd. All rights reserved.