This paper presents an approach to reconstruct solid models from triangular meshes of STL files. First, suitable slicing
planes should be selected for extracting parallel intersection contours, which will be used for solid model reconstruction.
Usually, a suitable flat region of triangular meshes of the STL model is selected as the bottom surface, and it can be fitted
into a plane from the selected flat region. The flat region is separated by a mesh segmentation method, which uses a
specified small threshold dihedral angle to divide all triangular facets into separated regions. Next, a series of parallel
slicing contours are obtained by cutting the STL model through specified parallel cutting planes. Slicing contours are
originally composed of a lot of line segments, which should be simplified and refitted into 2D NURBS curves for data
reduction and contour smoothing. The number of points on each slicing contour is reduced by comparing the variation of
included angles of each two adjacent line segments. Reduced points of each slicing contour are fitted into a NURBS
curve in commercial CAD software. Finally, with a series of parallel 2D NURBS curves, the solid model of the STL
facets is established by loft operations supplied in almost all popular CAD software. The established solid model can be
used for other post processing such as finite element mesh generation.