Research On The Key Techniques For Reverse Modeling Of Mechanical Parts

Integrating the Reverse Engineering (RE), CAD and Rapid Prototype (RP) techniques to construct a design platform, which helps to realize the digital design and rapid design for mechanical products, is very important and useful. The core of the platform is an intelligent and rapid RE-based CAD modeling system for mechanical parts. Development of such a platform will provide useful approaches for product improvement, innovation and rapid design. It will also enhance the design ability, shorten the design period, and improve the design quality.In order to develop a reverse modeling system for re-design of existing mechanical products, efforts have been made to reconstruct 3D surfaces models with extracted engineering features, from layer-measured 3D images of existing physical models (parts or products). The investigation utilizes the surface reconstruction and feature extraction technologies to build a closed loop system for reverse modeling of mechanical parts. It aims at the several key research problems in creating the CAD models for mechanical parts. This thesis presents studied new strategies and new techniques, and gives detail discussions on their applications. This research enriches the modeling theory and design technology for mechanical parts.Firstly, the thesis discusses the edge extraction and vectoring methods in order to get the contour profile of the cross-section, based on the digitalizing techniques of layer measuring. A new adaptive contour-tracking algorithm based on the dynamic square is presented to get the minimal planar region for 2-D scattered points. The use the directional angle between the contour segments as a searching operator shortens the searching time and keeps the microstructure feature.Secondly, a new 3-D triangulation approach is described, in which a serial of parallel section contours are treated with the emphases on triangulation for profile data loops between the adjacent sections. For this purpose, a new approach for computing feature points and analyzing shape features of section contours was developed. It dealt with the sharp changes between the adjacent sections via the transition loop and accessional region. The new method has the advantages to overcome the distortion of triangular net and can deal with the special structures,...