Geometric Error Modeling And Measurement Of Five-axis NC Machine Tools

This paper takes the geometric error of five-axis NC machine tools as the studying object. Based on the existing research achievements about error modeling and error measurement at home and abroad, geometric error model of five-axis NC machine tools is established. And the components and characteristics of error terms in the model are analyzed, also the design of error measurement scheme and method of error parameters identification are discussed.First of all, the current research situation of error modeling and measurement technology of NC machine tools is analyzed, meanwhile the advantages and disadvantages of various error modeling and measurement are compared. The error sources and types of NC machine tools are introduced, and the causes and components of geometric error are emphasized.Then, features are defined to describe the feature relationship between two neighbouring moving bodies. And body coordinates and moving coordinates between two neighbouring bodies are set up. The feature matrixes between two neighbouring bodies are analyzed when errors exist, and the feature matrixes are classified. Afterwards, the method of error modeling is introduced, and the process of error modeling is summed up. The types of NC machine tools, especially five-axis NC machine tools, are presented. And the definition method of coordinate axis of NC machine tools is described. Then geometric errors of five-axis NC machine tools are analyzed. The topology framework is set up, and the two error branches of machine tools are described. After that geometric error of five-axis NC machine tools is modeled, and the expression of first order error model is given. At last the error terms in the model are analyzed.Moreover, the data simulation of single error term is introduced. By observing the components and characteristics of error terms in the model, the error measurement scheme is designed to identify the error parameters. Errors are identified with mathematical approach in this paper, with which the number and process of error identification are reduced, and the efficiency is enhanced. According to the measurement scheme, the mathematical expressions of error terms in the model of NC machine tools are deduced.Finally, the example of error identification is given on the basis of the measurement scheme designed. The values of error parameters in the model are identified in terms of the values of error measurement from dX, dY and dZ. And it shows that the error measurement scheme designed in this paper can be used to solve the error parameters.