Error Evaluation And Error Compensation Of CNC On-line Inspection And Machining

With the rapid development of modern technology,especially the parts in the machinery manufacturing industry are becoming more and more complex,and the quality of parts is an urgent problem to be solved in the mechanical manufacturing industry.The error evaluation and the error compensation technology of the part machining are the key points to the quality of parts.Because of the traditional off-line scheme using coordinate measuring machines(CMM)to inspect the parts,there are the problems of the clamping error of the two times,and it is difficult to realize the inspection and evaluation of large parts.In this thesis,the error evaluation and the error compensation technology of NC machining are studied to realize the integration of “NC machining-measurement-error evaluation-error compensation".The evaluation of the simple shape contour error,the evaluation of the complex surface profile error and the complex surface error compensation technology are studied,the specifics as follow:(1)Establish a mathematical model for the error evaluation of the minimum zone method for a plane straightness,spatial straightness,roundness,cylindricity,sphericity and so on.The quasi Newton method is used to evaluate the algorithm,and the flow chart of each kind of contour error evaluation is given.(2)The mathematical model of the minimum zone of the complex surface profile error evaluation is established,and the complex surface profile error evaluation is converted to two times the maximum value of the minimum distance from the measured point to the theoretical surface.The minimum distance between the measured point and the theoretical surface is obtained by using the method of dividing approximation,and the theoretical surface is obtained by fitting cubic B-spline surfaces.Finally,the MATLAB iteration method is used to solve the nonlinear optimization problem of two times the maximum of the minimum distance from the point to the theoretical surface.(3)In order to improve the machining accuracy of the surface parts with complex surfaces,the machining error compensation technology of complex surface is studied.Based on the analysis of on-line inspection data,the empirical mode decomposition(EMD)is proposed to obtain the system errors and random errors.The NC codes are modified by the system errors,and then the machining accuracy is improved.(4)Develop the software of form error evaluation system.Based on(1)and(2)part of the simple shape of complex surface profile error evaluation and error evaluation of the related content,system software is developed,including a plane straightness error,spatial straightness error,flatness error,cylindricity error and sphericity error,complex curved surface profile error geometry evaluation content.The system has three function modules: error evaluation function,graphic real-time display function and data import and export.The result of error evaluation,the error map of each measuring point and the error result diagram are displayed on the system software interface in real time.The error result of each measuring point can be used by the system software.Finally,the correctness and effectiveness of the system software are verified by experiments.