A method of manufacturing a three-dimensional article includes (1) receiving a data file, (2) analyzing the data file, and (3) defining a support structure. The data file defines a hollow three-dimensional article to be formed from a build material. Analyzing the data file includes identifying an opening that converges to an apex along the sequence of layers. The opening is at least partly defined by an inside edge of the three-dimensional article. The support structure is attached to the edge and closes the opening. The support structure includes a structural sheet portion and an interface web portion. The structure sheet portion defines a majority of an area of the support structure except for a boundary contour between the structural sheet portion and the inside edge. The interface web portion closes the boundary contour and defines a weakness contour for removing the structural portion from the three-dimensional article.