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In order to solve the problem that the topological relationship between the triangular facets is lost when the 3D model is converted to STL files，in the process of reading and analyzing STL files, a fast topology reconstruction algorithm based on half-edges structure and hash table is proposed. In the process of reading data, a point table without repeat position information is established through a hash table, and a collection containing half-edges in which no adjacency facets are added is maintained therein. According to the set and topology algorithm, the topological relationship of the facets is improved, and the topological relationship of the facets is quickly established in the process of reading data.

In order to repair the normal vector error in STL file,this paper first classified the contours surrounded by the triangular facets with normal vector error into three types,respectively single closed contour,linked closed contours and nested closed contours. Then it repaired the normal vector error as follows: found the border edges of all the facets with normal vector error,found the closed contours formed by the border edges,marked the facets inside the contours,and reversed the direction of the normal vector of each facet inside the contour. It implemented and verified this algorithm by examples. The method proposed in this paper can be used in error detection and repair with STL file. [ABSTRACT FROM AUTHOR]

For the problem of complex surface prototype model making thin-walled parts, the three commonly used method of making the opponent plate and model were compared to study the key technology of rapid prototyping process, including : STL file format conversion formatting parameters and rapid prototyping key parameters set on the key issues of ordinary model, prototype thin- walled parts of complex surface models were discussed and compared. By curved wall thickness 0.5 mm part design and model making, ordinary parts and surfaces suitable for thin-walled parts rapid prototyping parts reasonable parameters were proposed. The results show that, as long as the proper selection of critical process parameters reasonably avoid surface thin wall fracture parts prone to rapid prototyping, multi glitch problems efficiently manufacture high-precision model, to meet the needs of the characteristic model. [ABSTRACT FROM AUTHOR]