Research On Reverse Modeling Technology Of Aviation Mold With Complex Scribed Lines

The traditional aircraft design and manufacturing model uses a large number of solid manufacturing basis to ensure the accuracy of aircraft manufacturing and the interchangeability and conformity in production process,which is a certain restriction to improve the productivity of aviation manufacturing enterprises and causes great pressure on storage,maintenance,management and many other aspects.In order to comply with the trend of digital transition,there is an urgent need to convert physical prototypes into digital manufacturing basis.The reverse engineering technology that reconstructs the product CAD model from the measurement data of existing physical objects has provide a good solution for this problem.This paper takes aviation mold with both the profile composed of free-form surface and complex scribed lines as the concrete object to carry out the research of reverse modeling of aviation physical manufacturing basis.The main research covers threedimensional digital measurement,multi-element measurement data preprocessing,digital modeling and so on.The specific research work of the thesis is summarized as follows:(1)On the basis of analyzing and summarizing the structural features and common design elements of aviation mould and other physical basis for manufacturing,the data acquisition work of the geometric shape and datum lines of physical object is executed using a visual comprehensive metrology approach that combines photogrammetry,structure light scanning and optical tracking contact measurement.The implementation process and strategy of the measurement scheme are presented in this paper.(2)The pretreatment methods of heterogeneous measurement data obtained during the data acquisition process were studied,focusing on the management of discrete sample points of scribed lines.According to the knowledge of statistics and graph theory,the grouping and sorting methods for measurement data of complex lines is proposed to make the organization of the data convenient for the subsequent modeling process,thus the efficiency of model reconstruction is improved.(3)Combining with the existing theory and method of curve and surface reconstruction in reverse engineering,the reconstruction of CAD model of aviation mold is realized with the professional CAD software as a main tool,supplemented by self-developed software.The general method and process of die reconstruction are summarized,which include reconstruction of main mould surface,reconstruction of complex line and fusion of curve and surface reconstruction result,etc.Base on it,the CAD model of concrete examples are rebuild and evaluated to confirm the effectiveness of the method.(4)The idea of constraint-based model reconstruction is introduced into the practice of reverse modeling of aviation mould.Solving the partial constraint satisfaction problem between curve and surface features in the process of model reconstruction has a certain optimization effect on the reconstruction model,which makes it closer to the original design intention of the product.