Study On The Comprehensive Evaluation Method Of The Geometrical Quality Of S-Shaped Test Piece

Complex surfaces are more and more used in industrial fields because of their special geometric and mechanical properties.However,it puts forward higher requirements for precision and efficiency for the high-end CNC machine tools that are used to machine the complex surfaces.The S-shaped test piece is a standard part used to test the dynamic accuracy and machining precision of five-axis CNC machine tools.In this paper,the inspection and evaluation of the form error and the micro topography error of the S-shaped test piece are systematically studied.It mainly includes the research on the form error inspection strategy,the research on the surface profile error evaluation algorithm,the researches on the sampling planning and the evaluation method of micro topography error.Firstly,a form error distribution model is established by analyzing the influence of geometric features of complex surface on machining.An error distribution model driven scanning line distribution strategy is proposed,in which the star-shaped scanning lines distribution is used in the sensitive area of the error distribution model and the number and length of scanning lines are allocated adaptively according to the importance of the sensitive area.Simulation and experiment results show that the sampling accuracy and efficiency of the proposed scanning line distribution strategy are superior to the traditional scanning line distribution method.Secondly,the profile error evaluation algorithm is proposed for the evaluation of profile error,which extracts evaluation key points to solve the problem of the data redundancy in evaluation.The deviation curve is decomposed into multiscale components by Wavelet Decomposition.Then,the medium and small scale components are used to select the evaluation key points.Using these key points,at last,the profile error is calculated based on the SQP algorithm.The proposed inspection and evaluation method is verified through experiments and the results shows that the proposed method can greatly improve the efficiency and accuracy of the inspection and the evaluation.Thirdly,by analyzing the influence of machining feedrate and geometric characteristics of tool path on the machining stability of complex ruled surface,the distribution model of micro topography error was established.According to the model,the sampling positions of waviness are planned and modified,as well as the length of sampling line is optimized.The filtering range and waviness evaluation parameters are determined according to the wavelength of the vibration mark on the surface of the Sshaped test piece.The experiment results show that the proposed sampling positions are conform to the areas with large waviness scale form error on the actual machined S-shaped test piece and the sampling line is shorter.It means that on the premise of achieving the same sampling accuracy,the proposed method improves the measurement efficiency.In order to realize the comprehensive measurement and evaluation of the geometric quality of S-shaped test piece,this paper takes the proposed algorithm as the core to program the software and integrates CMM,surface profiler and specific clamping table to build a comprehensive evaluation platform.It realizes data formatted input and output,original data sampling planning,machining error evaluation,formatted output of evaluation report,system software integration and other functions.The practicability of the platform is verified by an application example.Above all,the presented works propose systematic measurement and evaluation method of profile error and micro topography error for S-shaped test piece.It is proved by experiments that the proposed method has effectiveness.It provides theoretical basis and application means for the comprehensive evaluation of the geometric quality of Sshaped test piece.