Research Of Surface Profile Error Evaluation For Screw Rotor

Screw surface is one of the most widely used surfaces in the modern mechanicalindustry. Many parts of the screw surface features, such as screw rotor, whose surfacemachining accuracy impacts directly the mechanical overall performance. Therefore, thetechnologies of measurement and evaluation on the screw surface have always been animportant research topic in academia and business community at home and abroad.This paper studies the different methods of the commonly used surface contact andnon-contact measurement, the methods of the data processing and the probe radiuscorrection with contact measurement, the radius correction method called4pointsco-sphere.To the lack of screw surface measurement for coordinate measuring machines, thepaper launched a design research and development work of the screw rotor measuringinstrument. The design is based on the cylindrical coordinate system and the lasertriangulation methods, removes the impact of the probe radius. The measuring instrumentused a standard calibration ring gage which is concentric installation with the rotor tocalibration. It can complete the measurements of the type line shape as well as the scanmeasurements along the direction of the screw lines.Combination of various types of curve and surface fitting methods of the reverseengineering in recent years, the curves and surfaces can be reconstructed by the NURBSalgorithm. Only with the measured data, the parametric surfaces of the higher accuracy arefitted by using MATLAB software. The parametric surfaces reflect the measured surfacescontour information.The distance of the point and the theoretical curve is calculated by the normal vectorbound method and dichotomy. Combined with the Gauss-Newton algorithm to successiveapproximate to the minimum zone, the curve profile error is calculated. Based on theminimum zone method, the surface best matching state is reached by the loop iterations ofthe split-approximation method and the optimization algorithm of MATLAB software.Then the optimal solution of the surface shape error to meet the minimum zone method andthe surface profile error can be got.The research work on the rotor surface measurement, the data processing, the proberadius correction, the curve and surface fitting, the curve and surface profile errorevaluation and the research and development work of the non-contact screw surface measuring instrument has a certain theoretical significance and practical value.