Research On Theoretical Modeling And Compensation Strategies Of Three-axis CNC Milling Machine

The geometric errors of machine tools mainly come from the manufacturing and assembly processes,which are an important factor affecting machining accuracy.In order to analyze and study geometric errors more efficiently and accurately,the purpose of improving machining accuracy of CNC machine tools is achieved.In this paper,the three-axis CNC milling machine is taken as the research object,and the establishment of the comprehensive transfer model of geometric error and the separation model of compensable error,the measurement and identification of geometric error elements,the identification of key geometric errors,the design of error compensation technical scheme and the verification of compensation experiment are completed.All works and achievements are as follows:First,based on the multi-body system theory,the XKA714 × 17 / B three-axis CNC milling machine was analyzed for topology structure and was described for low-order volume array.The homogeneous coordinate transformation principle was used to list the feature matrices between machine bodies.Based on the relative pose relationship,a three-axis CNC milling machine spatial geometric error comprehensive transfer model was established;and an error model that can directly separate the compensable and uncompensable error sources was established based on the theory of rotation,so as to provide subsequent error compensation and accuracy design work theoretical basis.On this basis,in order to verify the accuracy of the established error model and the subsequent data support for key error identification and error compensation,The positioning error and straightness error of the three axis NC milling machine were measured by Renishaw xl-80 laser interferometer.According to the measured results,The Nine-line method was used to identify the errors,and all 21 geometric errors were obtained.Then,due to the different mechanism and degree of influence of different geometric errors on machining accuracy,in order to more effectively compensate or accurately design the geometric errors of the three-axis CNC milling machine,the orthogonal geometric design method was used to critical geometric errors of the three-axis CNC milling machine.According to the selected orthogonal table,variance analysis and range analysis are carried out on the test results,and 10 key geometric errors are obtained.Finally,based on the integrated error transfer model of the machine tool,the software error compensation methods of the three basic movement modes of the three-axis CNC milling machine are analyzed,and the respective NC system instruction correction methods for fixed-point,linear,and circular motions are obtained.In order to verify the accuracy of the compensation method,the error compensation experiments of the linear and circular motion compensation methods are carried out.The experimental results show that the positioning error and roundness error are significantly reduced,and the roundness error compensation rate reaches 35%,which verifies the feasibility and effectiveness of the compensation method.