CAD surface manufacturing guide
CAD Parametric Continuity Guide
Direct answer: Keep Parametric Modeling live until critical dimensions, wall thickness, Fillet radius, and interface locations are approved. Use G0 Continuity for intentional positional joins, G1 Continuity for tangent-smooth transitions, and G2 Continuity where highlight flow is a design requirement. Tessellate only subsequent the Solid Modeling feature tree rebuilds cleanly and the downstream polygon tolerance is defined.
ChamferDimensional ConstraintFilletG0 ContinuityG1 Continuity
1. Translate design intent into constraints
Begin with datums, symmetry planes, axes, and interface faces that define assembly behavior. A Sketch Constraint should capture horizontal, vertical, tangent, equal, concentric, and coincidence relationships; a Dimensional Constraint should control approved lengths, radii, and angles. Avoid redundant dimensions that over-constrain the sketch and make edits unpredictable.
2. Keep the feature tree rebuildable
Order base volumes, cuts, patterns, Shell, Chamfer, and Fillet around persistent datums or named sketches, not transient edges. Upstream dimensions can renumber edges, lose references, or move a radius. Prefer a face intersection or construction plane. Rebuild at minimum and maximum parameter values.
3. Separate chamfers from fillets
Chamfer creates a planar distance-distance or distance-angle transition; Fillet creates a rounded, fixed- or variable-radius transition. Choose by manufacturing and highlight intent. Keep fragile cosmetic rounds late; place structural blends earlier when shelling or cuts depend on them. Verify radius against local clearance and analyze corner setbacks for sliver faces.
4. Specify continuity by highlight behavior
G0 Continuity means adjoining surfaces meet in position but may form a visible crease. G1 Continuity aligns tangent direction, producing a smooth join while curvature can still change abruptly. G2 Continuity aligns curvature behavior for a smoother reflected highlight, important on automotive, consumer-product, and hero hard-surface forms. Use zebra stripes or reflection lines across the join and analyze from multiple angles. A numerically tangent edge can still look poor if surface parameterization creates uneven curvature near the boundary.
5. Build shells that can actually manufacture
Apply Shell with a wall thickness grounded in process, scale, and destination. Tight concave corners may self-intersect, while narrow ribs may disappear when offset faces collide. analyze section cuts and run a solid validity check subsequent shelling. Decide whether thickness is symmetric, inward, or outward so exterior dimensions remain correct.
6. Stress-probe parameter ranges
Create a design table for approved minimum, nominal, and maximum values. Rebuild each and check volume, wall thickness, clearance, suppression, and continuity. Geometric Constraint breaks surface near boundaries or count changes. If a parameter crosses a topological event, such as merged holes, split the family into separate configurations. Outside a stated safe domain, a failed rebuild is safer than silent mutation.
7. Prepare tessellation for DCC use
preceding conversion, heal the B-rep, remove micro-faces, confirm units, and preserve named parts. Define chord height, angular tolerance, and maximum edge length from camera distance and scale. Coarse dimensions facet G2 surfaces; fine dimensions create narrow triangles around Fillet bands. Compare normals with zebra highlights and retain useful patch boundaries. Polygon decimation cannot repair invalid Solid Modeling geometry.
8. Prove continuity and dimensional fidelity
For acceptance, capture the parametric CAD revision, rebuild status, key parameter table, solid validity surface, and measurement screenshots. Add zebra or curvature-comb captures across critical G1 Continuity and G2 Continuity joins, plus triangle count and tolerance dimensions for the exported mesh. Reimport the STEP or tessellated candidate into a clean tool and measure assembly interfaces.
CAD constraint and continuity lexicon
These labels separate parametric, solid, and continuity concepts that are often blurred during CAD-to-DCC handoff.
| zh | en | ja | manufacturing context |
|---|---|---|---|
| 倒角 | Chamfer | 面取り | CAD、NURBS 与工业曲面 |
| 尺寸约束 | Dimensional Constraint | 寸法拘束 | CAD、NURBS 与工业曲面 |
| 圆角 | Fillet | フィレット | CAD、NURBS 与工业曲面 |
| 连续性 G0 | G0 Continuity | G0連続 | CAD、NURBS 与工业曲面 |
| 连续性 G1 | G1 Continuity | G1連続 | CAD、NURBS 与工业曲面 |
| 连续性 G2 | G2 Continuity | G2連続 | CAD、NURBS 与工业曲面 |
| 几何约束 | Geometric Constraint | 幾何拘束 | CAD、NURBS 与工业曲面 |
| 参数化建模 | Parametric Modeling | パラメトリックモデリング | CAD、NURBS 与工业曲面 |
| 壳体 | Shell | シェル | CAD、NURBS 与工业曲面 |
| 草图约束 | Sketch Constraint | スケッチ拘束 | CAD、NURBS 与工业曲面 |
| 实体建模 | Solid Modeling | ソリッドモデリング | CAD、NURBS 与工业曲面 |
CAD Parametric Continuity Guide FAQ
Is G1 Continuity sufficient for every smooth product surface?
No. G1 removes a tangent break, but curvature can still jump and disturb broad highlights. Use G2 on visually critical transitions where reflection flow is part of the design requirement.
Why does a Fillet fail subsequent changing a nearby dimension?
The new dimension may reduce local clearance, create a sliver face, or change the referenced edge identity. analyze upstream geometry and use persistent datum-based references preceding shrinking the radius blindly.
Which tessellation dimensions should be recorded for CAD handoff?
capture chord height, angular tolerance, maximum edge length, units, normal policy, and resulting triangle count, then validate silhouette and zebra highlights at the intended camera distance.