| Error detection and compensation is an economical and effective method of improving the precision of CNC machine tools. The paper studies the geometric errors and dynamic performance of three-axis CNC milling machine based on DBB. The main achievements are as follow:Firstly, the establishment of coordinate system and main error factor of the CNC machine tools are analyzed. The geometric errors model of three-axis CNC machine tools was built by using Homogeneous coordinate transformation theory. A reference coordinate system and sub-coordinates are built on the machine base and Each saddle, the coordinates between the kinematic link from tools to bed and the kinematic link from work to bed are converted. Based on the ball bar detection theory, the error separation method of ball bar detection and the parameter model of errors are thoroughly studied. Then dynamic error simulation is done in different error conditions. The simulation figures provide a theoretical foundation for the error detection and compensation of the CNC machine tools.Secondly, the experiments of error detection for the machine tools by using ball bar are introduced, including preparation work, Installation and debugging, operation, data acquisition and analysis. In order to obtain accurate and complete data, detection model one and detection model two are designed. The results show that it is feasible using ball bar to detect the error of CNC machine tools. The method is easy and convenient to be used in practice.Finally, NC program correction method for three-axis CNC milling machine is proposed. Taking three-axis CNC milling machine as the experimental subject, error compensation software is developed. The laser interferometer and its analysis software is used to evaluate the compensation effect. Based on the numerical control system, the error which will affect the dynamic performance of machine tools is debuged and researched, and a simple and useful compensation method is proposed. The results show that the precision of CNC milling machine is improved effectively by using the proposed method. |
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