No published ratio
Industry tables exist. NetProto does not reprint one as a specification.
Rib to wall ratio
Rib to Wall Ratio: Size the Rib From the Skin, Not a Table
Mark nominal wall, rib thickness, and cosmetic faces. DFM review comments on CAD. This page does not publish a rib-to-wall ratio.
Design guideline
The rib is a fraction of the wall, not a second wall
A rib that is as thick as the wall makes a hot junction and a sink risk on the opposite face. This page owns the ratio question. It does not publish a number. The ribs page owns the feature.
Rib to wall ratio sizes the rib from the skin, not a table. It is the rib thickness versus the nominal wall. A rib as thick as the skin makes a hot junction and can sink the opposite face. Rib design owns the feature. Wall thickness owns the skin. Sink marks is the defect. DFM review needs both thicknesses.
This spoke owns the ratio question. NetProto does not publish a ratio as a specification. Gussets and fillets change the junction. The design guide hub lists every topic.
Roles
Which page answers which rib question
Stay here for the ratio question. Open a sibling for the rib feature, the wall, or the sink.
| Page | Use it for |
|---|---|
| Rib to wall ratio (this page) | Rib thickness versus the nominal wall |
| Rib design | The stiffening feature |
| Wall thickness | The skin you size from |
| Gussets | Triangles that are not full ribs |
| Fillets and radii | Root mass at the junction |
| Draft angle | Rib sidewalls need draft for release |
| Sink marks | The read-through on the opposite face |
| Uniform wall thickness | Even walls before you add ribs |
| Boss design | Posts that tie into ribs |
| DFM review | CAD check before steel |
Checks
What DFM review looks for on rib-to-wall ratio
Qualitative checks. No figure on this page is a NetProto specification.
Skin first
Set the nominal wall, then size the rib from that wall.
Junction is local mass
Root radius and a thick rib both add a hot spot.
Class-A faces matter
A sink on a show face is a different risk from a hidden cover.
Decision
A rib as thick as the wall versus a thinner rib
Wrong: a second wall standing on the skin. Right: a thinner rib, a rounded root, and a marked cosmetic face.
What goes wrong
- A rib drawn as thick as the nominal wall
- No note on the opposite cosmetic face
- A ratio copied from a blog and treated as a spec
What to try first
- Size the rib from the skin, then add draft and root radius
- Mark class-A faces that cannot take sink
- Upload CAD so DFM review can comment before quoting
RFQ
Mark these on CAD before uploading for DFM review
The quote can start from CAD alone. These notes make the ratio pass specific.
Nominal wall thickness on the ribbed face
Rib thickness, height, and spacing
Root radius at the junction
Opposite-face cosmetic class
Resin family, including glass fill
Boss or gusset tie-ins on the same wall
Related
Related design guidelines
Stay on this spoke for its question. Open a sibling for the neighbor topic or the CAD check.
Sink marks
The read-through on the opposite face.
Sink marksDFM review
How NetProto reads rib and wall on CAD.
DFM reviewFAQ
Rib to wall ratio FAQ
What is rib to wall ratio?
It is rib thickness compared with the nominal wall. A thicker rib stiffens more and raises sink risk. This page owns that tradeoff.
What ratio does NetProto publish?
None. Industry tables exist. They are not a NetProto specification. Upload CAD so DFM review can comment on your wall, resin, and class.
Why do thick ribs sink?
The junction is locally thicker than the skin. That mass cools slowly and can pull the opposite face. The sink article owns the defect.
Can a thick rib be fixed by adding a fillet?
A fillet spreads the junction mass and reduces stress concentration. It does not eliminate sink risk if the rib is much thicker than the wall. Open fillets and radii for the root geometry.
Do glass-filled grades change the ratio?
Filled grades change shrink and stiffness. They do not create a published NetProto ratio. Name the family on the RFQ.
How is this page different from the ribs page?
This spoke owns the ratio question. Ribs owns the feature: height, draft, spacing, and boss tie-in. DFM review checks CAD.
What information should I mark on CAD for rib-ratio review?
Show nominal wall, rib thickness and height, root radius, and opposite-face cosmetic class. Upload CAD so DFM review can comment before quoting.
Next step
Upload CAD for DFM review of rib-to-wall sizing
Share the wall, the ribs, and cosmetic faces so review can comment before quoting.