Downloaded from https://www.everyspec.com APPENDIX C MIL-STD-31000A C.7.2.14. Unused patches (G-SU-UN). Definition: Surface entity contains patches that are not used in any face of a solid. Unused patches are generally produced when the bounded face of a solid is much smaller than the surface defining the face. Measurement: N = number of unused patches Figure 11-Example of an unused patch (in this case, patch 2) Effects of condition on CAD data quality: Design and drafting: Unused patches unnecessarily increase model size and may cause unpredictable errors. Data exchange: The receiving system may be confused by unused patches. Finite element analysis: Unwanted elements may be generated.
Numerically controlled manufacturing: Unwanted tool motion may be produced. Recommended correction: Divide the face surface along a patch border and delete the surface that is not part of the patch. C.7.2.15. Folded surface (G-SU-FO). Definition: The maximum angle between pairs of normal vectors, θ, in either parametric direction of a patch or surfaces exceeds the allowable limit. Generally normal vectors of a surface uniformly face in nearly the same direction, either into the solid or out of it. Effects of condition on CAD data quality: Design and drafting: Offsetting of surfaces may fail. Models may become unstable. Data exchange: Solids may fail to sew.
Face boundaries may have inverted normal vectors. 100