Vent or go through
A closed pocket burns or shorts if gas cannot leave.
Blind holes
Blind Holes: Closed Pockets Need Vent and Draft
Flag blind pockets on CAD. DFM review checks vent, draft, and whether the pocket should become a through hole.
Design guideline
One end is closed. Air has to leave somehow.
A blind hole traps air unless steel vents it. Deep pockets need draft on the side walls. Through holes vent naturally when both ends reach the split. This page covers the closed pocket.
A blind hole is a pocket closed on one end. It must vent to atmosphere or the parting line through steel. Venting owns the gas path. Through holes own the open alternative. Bosses own the post. DFM review needs pocket depth and nearby wall.
This page covers the closed pocket. Coring out is how you hollow a thick island, which may leave more blinds. The design guide lists every topic.
Roles
Which page answers which blind-hole question
Stay here for closed pockets. Open a related guide for through holes, vents, draft, or the boss.
| Page | Use it for |
|---|---|
| Blind holes (this page) | Closed pocket, vent, draft |
| Through holes | Open both ends to the split |
| Side holes | Axis off the pull |
| Venting | The gas path |
| Boss design | The post that often holds the pocket |
| Draft angle | Draft on pocket walls for release |
| Wall thickness | A blind in a thin skin is a risk |
| Hole shapes | The outline of the pocket. Not the closed end. |
| DFM review | CAD check before steel |
Checks
What DFM review looks for on blind holes
Qualitative checks. No figure on this page is a NetProto specification.
Draft the walls
Deep blinds scuff on eject without draft.
Thin-wall blinds
A pocket in a thin skin can sink or punch through. Mark those.
Threads are separate
A molded or tapped thread is not a plain blind hole. Open molded-in threads or boss design for those features.
Decision
A closed pocket versus opening the hole through
Wrong: a deep blind in a thin wall with no vent. Right: draft the pocket, vent it, or open it through.
What goes wrong
- A deep blind with no vent path
- A blind pocket in a thin cosmetic wall
- Assume every blind needs a vent pin
What to try first
- Open the hole through when function allows
- Draft the walls and flag the pocket on CAD
- Let tooling pick vent pins, parting vents, or porous steel
RFQ
Mark these on CAD before uploading for DFM review
The quote can start from CAD alone. These notes make the DFM pass specific.
Blind pockets called out
Which pockets can become through holes
Nearby wall thickness
Cosmetic faces opposite the pocket
Thread or insert intent, if any
Resin family
Related
Related design guidelines
Related guides for the next question, plus a CAD check when you are ready.
DFM review
How NetProto reads closed pockets on CAD.
DFM reviewFAQ
Blind holes FAQ
What is a blind hole in molding?
A pocket closed on one end. It traps air unless steel vents it. Through holes vent when both ends reach the split.
Can blind holes be threaded?
A thread is a different feature. Open the thread or insert pages. This page covers the pocket.
Do blind holes always need vent pins?
They need a vent path. That may be a pin, a parting vent, or porous steel. Tooling picks the method. Flag the pocket.
Are blind holes OK on thin walls?
They can sink or punch through. Mark them. Wall thickness owns the skin.
Should I just open the hole through?
If function allows, yes. Through holes own that path.
How is this page different from through holes or venting?
This page covers the closed pocket. Through holes own the open alternative. Venting owns the gas path. DFM review checks CAD.
What depth-to-diameter ratio is acceptable for a blind hole?
There is no universal spec. Deep blinds need a vent path and draft. Flag the pocket on CAD so DFM review can check tooling scope before quoting.
Next step
Upload CAD for DFM review of blind pockets
Share closed pockets and nearby walls so review can check vent and draft before quoting.