Hoop, not a beam
The whole ring flexes. Do not size it like a cantilever.
Annular snap fit
Annular Snap Fits: Hoop Deflection Around a Ring
Mark the ring, the mate, and whether the hoop can strip. DFM review comments on CAD. This page does not publish an interference spec.
Design guideline
The ring flexes all the way around
An annular snap retains by hoop deflection, not a single beam. Uneven wall ovals the ring and changes feel. This page owns the ring. Cantilever owns the beam.
Annular snap fit is hoop deflection around a ring, not a single beam. Caps and lids use that ring. Keep the wall even so the hoop does not oval. Cantilever snaps own the beam. Uniform wall thickness owns the skin. DFM review needs the mate.
This spoke owns the ring. Assembly features is the map. Undercuts own whether the hoop strips or needs an action. The design guide hub lists every topic.
Roles
Which page answers which snap question
Stay here for the hoop. Open a sibling for the beam, the wall, or the CAD check.
| Page | Use it for |
|---|---|
| Annular snap fit (this page) | Hoop deflection around a ring |
| Cantilever snap fit | A hook on a flexible beam |
| Assembly features | Which molded joint to pick |
| Uniform wall thickness | Even wall so the ring stays round |
| Undercuts | Whether the hoop needs an action |
| Living hinge | A molded hinge, not a snap |
| DFM review | CAD check before steel |
Checks
What DFM review looks for on annular snaps
Qualitative checks. No figure on this page is a NetProto specification.
Wall evenness
A thick island on one side ovals the ring and changes retention feel.
No published interference
Retention is not a NetProto spec. Mark the mate on CAD.
Strip or action
Some hoops strip on ejection. Others need a lifter or side action.
Decision
An even hoop versus an oval ring
Wrong: a thick gate island on one side of a cap ring. Right: even wall, a marked mate, and a release path.
What goes wrong
- A thick gate pad that ovals the snap ring
- No mate part for the hoop
- A cantilever rule copied onto a full ring
What to try first
- Keep the wall even around the ring
- Upload both halves so DFM review can comment
- Open cantilever only if the joint is a beam
RFQ
Mark these on CAD before uploading for DFM review
The quote can start from CAD alone. These notes make the hoop pass specific.
Ring location and whether it is internal or external
Mate part CAD or key diameters
Wall evenness around the hoop
Whether the hoop can strip on ejection
Resin family, including PP or PE if used
Cosmetic class on the cap face
Related
Related design guidelines
Stay on this spoke for its question. Open a sibling for the neighbor topic or the CAD check.
DFM review
How NetProto reads hoop and mate CAD.
DFM reviewFAQ
Annular snap fit FAQ
What is an annular snap fit?
A hoop that flexes around a ring to retain a mate. Caps and lids use it. It is not a cantilever beam.
Do annular snaps need perfectly round parts?
Roundness and even wall matter more than a perfect CAD circle. Oval distortion changes feel. Upload CAD so DFM review can comment.
How is this different from a cantilever snap?
A cantilever is one beam and hook. An annular snap is a hoop. Open the cantilever page for the beam. This spoke stays on the ring.
Can retention change after T1?
A late retention change is steel work. Lock the mate and the hoop before the layout freezes.
Are closures always polypropylene?
Many caps use PP or PE families. That is not a published spec. Name the resin on the RFQ.
What information should I mark on CAD for annular-snap review?
Show the ring, the mate, wall evenness around the hoop, and whether it can strip. Upload CAD so DFM review can comment before quoting.
Next step
Upload CAD for DFM review of annular snaps
Share the ring and the mate so review can comment on the hoop before quoting.