What is the recommended setting to avoid failures when removing a face adjacent to a blend face in a shell?

Adding a shelf face at the tangent edge is a recommended setting to avoid failures when removing a face adjacent to a blend face in a shell because it provides structural integrity and smooth continuity at the connection between blended areas and the adjoining surfaces. When a blend face is present, it often creates complex geometries that can lead to issues during face removal operations. By introducing a shelf face, the geometry is reinforced, making it easier for the software to compute the new geometry and maintain the shell's integrity after the removal process. This addition can simplify the modeling complexities and enhance the overall stability of the shell, thus reducing the likelihood of errors or failures during editing.

In contrast, extending the tangent face may not always provide sufficient definition where the surfaces meet, increasing the risk of geometric ambiguity. Increasing the tolerance could lead to unintended consequences by allowing greater deviations that may compromise the design. Resolving self-intersections using patches can help in complex shapes, but it may not directly address the specific issues related to the adjacency of blend faces and enhance stability as effectively as adding a shelf face would.