Downloaded from https://www.everyspec.com APPENDIX C MIL-STD-31000A C.7.2.2. Non-tangent surfaces or patches (G 1 discontinuity) (G-SU-NT). Definition: Tangent angle changes at the common boundary between adjacent surfaces or patches. Measurement: angle between normal vectors at the common boundary, Δθ. Effects of condition on CAD data quality: Non-tangent surfaces or patches are not necessarily indicative of poor data quality. In some cases, such as square corners, chamfered, and beveled edges, non-tangent conditions are intended. When curves are intended to be tangent, but aren’t, then G 1 discontinuity is indicative or poor quality.
Non-tangent conditions are usually visible to the unaided eye and can be felt by finger tips on physical models. Design or drafting: A quality defect only when tangency is intended. Data exchange: No harmful effects on data exchange. Finite-element analysis: No harmful effects on mesh generation or model solution. Numerically controlled manufacturing: Sharp edges should generally be avoided in manufacturing. However, when making machine parts, removal of sharp edges may be covered by a general note or specification. When tangency is intended between surfaces, non-tangent surfaces produce noticeable defects in finished products. Recommended correction:
CAD operator must adjust one or both surfaces to eliminate the unwanted condition. 92