Generalized Kinematics Error Prediction of CNC Milling Machines by Using Simulation Method

Abstract

Nowadays, precision mechanical products manufacture has become a necessity in daily life. Consequently, high accuracy CNC machines in modern manufacturing systems are always required. Geometric (kinematic) errors, cutting tool dimensions, and thermal errors generated during machining are three sources of error that affect the accuracy of CNC milling machines. Many studies have been presented on CNC milling machine geometric (kinematic) error prediction to increase product accuracy. In this paper, the authors proposed a method with the primary purpose of using kinematic equations to predict generalized kinematic errors of CNC milling machines. Therefore, it can be applied to solve the requirements of designing high-precision CNC milling machines with long-term working ability. The kinematic modeling for the multi-body system of the CNC machine system is built based on the kinetic theory of Dennavit - Hartenberg (D-H). Using the Dennavit - Hartenberg (D-H) parameters to set the transfer matrices that define the position of the tooltip and workpiece. Then, by considering additional error parameters, the authors develop a method to determine the error based on the forward position kinematics equations for CNC milling machines. In this study, the authors used the Monte Carlo method to calculate and simulate the maximum generalizes kinematic error from the kinetic equations. In addition, the position errors for each stage of the CNC milling machine have been determined by experimental measurement using precision measuring instruments. Finally, the error results from the survey are compared with each other to decide on the method's accuracy and effectiveness.