Generation of Solid Models with Surface Properties from Scanned Triangular Meshes of Castings

Abstract

Reverse engineering which is a process to create solid models of products from their physical models using 3D scanning is necessary to produce high quality products. The models resulting from the reverse engineering are used in re-design, duplication, performance analysis, inspection and so on. On the other hand, castings are used in a wide range of machining products. Castings consist of casting surfaces and machining surfaces, and in the use of the castings, precise machining surfaces are required. However, precision is often not strictly required for the casting surfaces. Therefore, a reverse engineering method based on the separation of casting and machining surfaces has the potential to realize efficient reverse engineering of castings. Moreover, the solid models with rich surface information, such as casting surface, machining surface, screw thread surface, through hole, small feature and so on, are suitable for efficient use of the solid models. Much research on reverse engineering has been conducted in the last several decades [2-3],[5], however, efficient reverse engineering based on the surface separation and creation of solid models with rich surface information considering the application of solid models have not been realized. A research develops the reverse engineering method based on the surfaces separation for castings [4], however, the methods can only extract planar and cylindrical surface from castings, therefore, additional surface extraction and recognition methods are required for generation of solid models with surface information. In this paper, an efficient generation method of solid models with surface information based on the surface separation [4] from the scanned triangular meshes of castings is proposed. The proposed method consists of the following functions, and the overview of our method is shown in Fig. 1. 1) Separation of the scanned triangular mesh surfaces into casting surfaces and machining surfaces, and extraction of machining planar surfaces and cylindrical surfaces [4] 2) Extraction of the screw threads, through holes, and small features between the machining surfaces 3) Boundary modification of the casting surfaces for solid model generation, and alignment of the machining surfaces 4) Creation of the solid model from the extracted surfaces using Boolean operation