Rhino 3D Tip: Wall thickness and normal verification for 3D printing

Before you export for 3D printing, verify wall thickness and normals to avoid weak parts, print failures, or odd shading.

Why it matters

• Structural integrity: thin walls fracture or warp.
• Printability: inverted or inconsistent normals confuse slicers.
• Surface quality: incorrect normals cause shading artifacts and mask geometry issues.

Fast pre-checks

• Set units and tolerances: File > Properties > Units. Use real-world units; absolute tolerance 0.01–0.1 mm (or per printer spec).
• Find open/bad geometry: SelOpenPolysrf, SelBadObjects.
• Reveal gaps: ShowEdges (Naked edges). Cap planar holes with Cap. Clean faces with MergeAllFaces.

Analyze wall thickness

• Run ThicknessAnalysis on closed parts. Set the minimum value to your printer’s spec (e.g., 1.0 mm) and read the color legend for thin regions.
• Spot-check with Section and Distance for known stress paths (e.g., around holes, fillets, and sharp transitions).
• Use ClippingPlane to inspect interiors and confirm ribs, bosses, and hollow regions meet minimums.

Fix thin areas

• NURBS solids:
  • OffsetSrf Solid=Yes to uniformly thicken in or out.
  • Shell to hollow a solid while keeping a consistent wall.
  • Local reinforcements: OffsetSrf on selected faces, then BlendSrf or FilletEdge to transition smoothly.
  • MoveFace for simple planar offsets without remodeling.
• Meshes:
  • OffsetMesh to thicken uniformly; verify result with ThicknessAnalysis.
  • Weld to fix split vertex normals that create false “thin” readings; then smooth or relax locally if needed.
• SubD:
  • ThickenSubD (Rhino 8) for consistent walls on organic forms.
  • Alternatively ToNURBS, then use Shell/OffsetSrf for precise control.

Verify normals and orientation

• NURBS: Use Dir to display arrows. UnifyNormals for consistent outward-facing normals; Flip where required. Closed solids should point outward.
• Meshes: UnifyMeshNormals, then Weld at a reasonable angle (e.g., 180°) to prevent shading seams. Use CheckMesh/RepairMesh to fix non-manifold edges and inconsistencies.
• Re-check visuals in Rendered or Shaded modes; inverted patches should be obvious.

Export confidently

• STL/3MF: Export Selected, set mesh quality appropriately (avoid overly coarse facets that “eat” thin features).
• Re-import the file to sanity-check normals and wall thickness one last time.

Pro tips

• Maintain a printer-specific checklist (min wall, hole diameters, overhang, and tolerance ranges).
• Name and save analysis settings; use NamedSelections to revisit problem areas quickly.
• For batch jobs, consider a Grasshopper definition to flag thickness violations and generate color-coded previews.

Need guidance choosing the right Rhino version or add-ons for inspection and 3D printing? Explore NOVEDGE, or get expert advice and licensing through NOVEDGE. If you integrate rendering or visualization during checks, see compatible tools at NOVEDGE Rendering.