Research On Several Geometric Error Assessment And Surface Machining Error Separation Technologies

With the updating of modern manufacturing technology and the continuous progress of science and technology,high quality,high precision and high efficiency have become new requirements for the production and application of complex parts.One of the most important problem is the research on the evaluation and compensation technology of machining errors of parts.Although the inspection technology based on CMM is quite mature,and it can accurately measure the geometric error of parts,there are still problems of error evaluation method and insufficient evaluation accuracy.At the same time,due to the existence of various error sources,the accuracy of the complex curved surface of CNC machining is affected,which is not conducive to improving production efficiency.Therefore,it is necessary to study the error evaluation and error separation technology of complex curved surface.In this paper,several aspects of geometric error evaluation and error separation technology for complex surfaces are studied,including the following points:(1)In the framework of the new generation of error system standard,the minimum area method in line with the principle of minimum conditions is adopted,and the coordinate rotation method is used to create the precise fitting plane,and the geometric error evaluation mathematical models such as flatness,inclination,perpendicularity is established.The above errors are evaluated by a PSO algorithm with self-adaptive weight adjustment according to the degree of premature convergence of particles and a hybrid optimization method of fmincon function,and the flow chart of each error evaluation is given.(2)Starting from the definition of the minimum containment area of positioning,the coaxiality error is transformed into cylindricity and roundness error for evaluation.The size of the relative position between the center of the measured cylinder section and the measured axis is calculated,and the coaxiality error is taken as twice of the distance between the two positions,so as to establish the mathematical model of coaxiality error evaluation.The coaxiality error is evaluated by using a cuckoo algorithm with less parameters and easy to solve the continuity optimization problem.Through the analysis and calculation of the measured cylinder profile dimension data,compared with the literature data and other algorithm results,the validity and accuracy of the evaluation method are proved,and the visualization results and flow chart are provided.(3)The error separation technology of complex surface machining is studied.Aiming at the problem of error source in machining error(complete ensemble empirical mode decomposition with adaptive noise,CEEMDAN)algorithm is used to decompose machining error into systematic error and random error.Firstly,the on-line inspection technology is used to obtain the information of curved surface measuring points and the machining error signal,which is decomposed by CEEMDAN algorithm.Then,according to the correlation degree between the system error signal and the processing error signal,the IMF of each natural mode component is analyzed by using the method of autocorrelation analysis and spectrum analysis.By setting the threshold value,we can judge whether there is systematic error in each component,then reconstruct the signal with systematic error,and separate the original error signal into systematic error and random error.Through the simulation experiment,it is verified that the proposed separation method can effectively separate the systematic error signal.Finally,through the example of machining surface parts,the separation of complex surface machining error is realized.(4)Develop the software of form and position error evaluation system.Based on the related contents of(1)and(2),the system software includes the evaluation contents of flatness error,inclination error,perpendicularity error,coaxiality error and so on.In this system,three function modules,error evaluation function,graphics real-time display function and data import and export function,are integrated.The error evaluation results,error diagrams of each measuring point and error result diagrams can be displayed on the system software interface in real time,and the error results of each measuring point can be exported and used through the system software.Finally,the correctness and validity of the evaluation function of the system software are verified by the measured data.