Downloaded from https://www.everyspec.com APPENDIX C MIL-STD-31000A Discontinuous curvature is a quality defect only if adjacent surfaces are intended by designers to have continuous curvature. Design or drafting: A quality defect only when curvature continuity is required. Data exchange: No harmful effects on data exchange. Finite-element analysis: No harmful effects on mesh generation or model solution. Numerically controlled manufacturing: Curvature discontinuity is visible in finished parts. No effect on machining operations. Recommended correction: Adjust one or both faces to eliminate the unwanted condition. C.7.6.4. Self-intersecting shell (G-SH-IS). Definition:
A surface or patch intersects itself at one or more locations. The criterion is true of the shell does not intersect itself within specified precision. Effects of condition on CAD data quality: Design and drafting: Self-intersecting shells can’t be physically manufactured. Data exchange: Faces may not trim properly. Finite element analysis: Automatic mesh generation will fail. Numerically controlled manufacturing: Self-intersecting shells can’t be physically manufactured. Recommended correction: Remove the self-intersecting faces and recreate them in a way that does not produce a self-intersection.
Trim the self-intersecting portion of the shell provided that a sharp angle condition doesn’t occur. 116