Pin, slot, or window
A circle on CAD quotes as a pin. A slot or window quotes as shaped steel. Draw the outline you actually need.
Hole shapes
Hole Shapes in Injection Molding: Slots and Windows Change Steel and the Quote
The quote follows the steel that forms the opening. Draw a pin, a slot, or a window. DFM review comments on your CAD before quoting.
Design guideline
The quote follows the steel that forms the opening.
A round hole is usually a core pin. A slot or window is different steel, a longer shutoff, and a different DFM note.
Call the true outline on CAD. If DFM review only sees a circle, the quote assumes a pin. A slot, rectangle, or irregular window needs shaped steel or an insert. Through holes , blind holes , and side holes still decide pull and vent. This page decides what the opening does to steel. DFM review comments on your CAD.
A thread is not a hole shape. Open molded-in threads . Sharp corners on a window belong on fillets and radii . Thin stock between openings or to the edge is a wall thickness risk, not a published spacing table. The design guide hub lists every topic.
Roles
Which page answers which hole question
Stay here for the opening outline and the quote. Open a sibling for pull, threads, or corners.
| Page | Use it for |
|---|---|
| Hole shapes (this page) | Round pin versus slot, window, or irregular opening |
| Through holes | Both ends open to the split |
| Blind holes | Closed pocket, vent, draft |
| Side holes | Axis off the pull |
| Molded-in threads | A joint, not a hole outline |
| Fillets and radii | Corners on a slot or window |
| Draft angle | Release on long slot walls |
| Parting line | Where a long shutoff lands |
| Wall thickness | Stock between openings and to the edge |
| DFM review | CAD check of the true opening before quoting |
Quote
What DFM review looks for on hole shape
Qualitative checks. No hole spacing figure on this page is a NetProto specification.
Shutoff length
A long opening has more shutoff to flash and more steel to align. Mark mates and nearby cosmetic faces.
Stock around the opening
Thin ligaments between holes or to the edge break, warp, or fail to fill. Flag tight stock. Do not invent a spacing number.
Corners and pull
A knife-edge window corner is a fillet and a shutoff problem. Long walls still need draft. Through, blind, or side still applies.
Decision
Assume a round pin versus mark the true opening
Wrong: every hole quotes as a pin. Right: the outline on CAD matches the steel that will form it.
What goes wrong
- A slot drawn as a circle quotes the wrong steel
- A window with knife-edge corners flashes and cracks
- Openings packed so the wall is a thin web
- A thread treated as a plain hole with no release plan
What to try first
- Draw the real outline: pin, slot, or window
- Radius inside corners and draft long walls
- Leave stock between openings and to the edge
- Send threads to the thread page, not this one
RFQ
Send these notes with CAD for a hole-shape review
The quote can start from CAD alone. These notes stop a slot from quoting as a pin.
Which openings are round pins, slots, or windows
Which openings are mates or cosmetic
Pull direction and whether any opening is blind or off-draw
Corners that must stay sharp versus corners that can take a fillet
Tight stock between openings or to an edge
Thread or insert intent, if any
Related
Related design guidelines
This page owns the opening outline. Open a sibling for pull direction, threads, or the CAD check.
DFM review
How NetProto reads hole outlines on your CAD before quoting.
DFM reviewDesign guide hub
Rule index for every injection molding design topic.
Design guide hubFAQ
Injection molding hole shapes FAQ
Does hole shape change the quote?
Yes when the opening is not a round pin. A slot, rectangle, or window usually needs shaped steel or an insert, a longer shutoff, and more DFM notes. Upload CAD so review can see the true opening.
Is every molded hole a core pin?
DFM review treats a round, on-draw opening as a pin unless CAD shows otherwise. Do not leave a slot drawn as a circle. The quote follows the steel that actually forms the hole.
How is this different from through, blind, or side holes?
Those pages own whether the hole is open, closed, or off the pull. This page owns the outline of the opening and what that does to steel and the quote. You still need both.
Are threaded holes a hole shape?
No. A thread is a joint and a mold action. Open molded-in threads. Stay here for the plain opening: round, slot, or window.
How close can holes sit to each other or to an edge?
NetProto does not publish a spacing or edge-distance figure. Thin stock between openings or to the edge is a warp, fill, and break risk. Mark tight ligaments on CAD and let DFM review comment.
Do slots and windows need draft and radii?
Yes. Long walls still pull with the steel, so they need a release plan. Sharp inside corners on a window are a stress and shutoff risk. Open the draft and fillet pages for those rules.
Next step
Upload CAD for DFM review of hole shapes
Share the true opening outline, mates, and pull direction so review can see whether steel is a pin, a slot, or a window before quoting.