Research On Pattern Flattening For Parts With Complex Surfaces

In recent years, in some manufacturing fields such as the production of airplanes, vehicle, ships, clothes, shoes and toys, complex surface flattening technology has been wildly applied in the design and calculate of blank materials. With the development of computer aided design technology (CAD) and the adoption of advanced manufacturing technology, designer could design many curve-structure products with high-quality and graceful form. However, this brings new demands to the traditional calculation of blank.This thesis tries to realize the initial shape which has the same topology structure as the complex surface by the use of two initial flattening methods based on triangulate and vertex. The writer makes some improvement and adjustments to the develop optimization method based on Spring-Mass system, realizing the time step's self-adaptive choose in the process of optimization. Besides, the writer also presents the Global Adjustment Algorithm for the rolling region of triangulates, which could eliminate the rolling triangulate in the initial projection and optimization quickly and effectively for an orderly developed mesh surface on the basis of the initial flattening pattern of the surface. Efforts are also devoted to the study of material in the process of consistent with the actual situation in the deformation of the material flattening.On the basis of the global optimization of angles in the surface, a new approach is proposed- the global optimization of lengths in the surface, to get the form of mesh surface after the flattening of discrete curve surface. This method is called LBF(Length-Based Flattening)method for short. LBF defines the flattening problem as an optimization problem of the constraint problems whose paradigms are all the length of the mesh surface of the discrete curve surface. Compared with the previous approaches, LBF method is more stable and more capable of controlling the local precision in flattening process.With the above technologies, the writer develops a module named"Approximately Flattening System for Complex Surface"based on Windows NT/2000/XP and CATIA V5 and with the help of Visual C++, thus realizing the flattening of complex surface, automatic drawing of the flattened design and the auto-generation of error cloud atlas reality and data for surface. The program deals with interfaces: the structure information data is the DAT from CATIA V5 system; 2-dimension flattening model is shown by the CATIA V5; the error file is automatically created by system and error map is shown by the error display module use the corresponding error file.