Gate on visible cosmetic surface
- Witness mark and vestige need texture or offset design
- Pack marks may telegraph near the gate
- Trim or post gate removal adds handling
Glossary
What Is a Gate? Injection Molding Explained
The gate is the restricted entry that sets fill, pack, and witness marks on the part.
Glossary
The gate is the controlled entry where plastic enters the cavity
Gate style and location drive weld lines, shear, and trim scars.
Every gate is a intentional restriction. It shears material entering the cavity and sets how pack propagates.
Gate location should be chosen with cosmetic faces and weld line maps in mind, not added after the mold is steel cut.
Edge gates, tab gates, and hot drop gates leave different witness marks and need different trim or automation plans.
Glossary
How gate shows up on real programs
Library photos illustrate molding and tooling context for this term.
- Use the term in RFQs with geometry and material context, not in isolation.
- Link to the design guide when the term affects steel or part design.
- Upload CAD when the term changes tooling scope or piece price.
Appearance
Gate on a hidden edge versus cosmetic face
Moving a gate later costs steel and schedule.
Gate on hidden parting or edge
- Easier to hide vestige with break edges
- Weld lines can still cross visible faces if fill path is wrong
- Still requires DFM review for stiffness and fill
RFQ
Gate assumptions to document on day one
Mold designers use these notes when proposing gate location.
Cosmetic faces that cannot accept gate vestige
Assembly side that must stay clean for seals or labels
Fill direction constraints from living hinges or thin lips
Allowance for hot runner drops if manifold is in scope
Go deeper
Where this term connects
Each link is a different angle on the same program, not a duplicate definition.
Valve gate
Timed shutoff for large parts and sequential fill.
Valve gateRunner
Feed path upstream of the gate.
RunnerDesign guide hub
Gate location and weld line planning.
Design guide hubSink marks article
When pack cannot reach thick sections after gate freeze.
Sink marks articleVisual reference
Photos from molding and tooling programs
Images are selected from the NetProto Forge media library for this topic.
Injection molded production parts on a tray
Injection molded production parts on a tray
Engineer reviewing a molded part drawing
Engineer reviewing a molded part drawing
Plastic housing components from a steel tool
Plastic housing components from a steel tool
FAQ
Gate questions
Can buyers pick gate location unilaterally?
State constraints in project notes. Mold designers propose location on qualified tooling programs.
Do weld lines always mean a bad gate?
Not always, but weld lines on structural or cosmetic faces need explicit acceptance.
Does gate size affect material degradation?
Small gates increase shear. Sensitive resins need gate sizing matched to process windows.
Next step
Align gate talk with DFM
Upload CAD with cosmetic and assembly faces marked before approving steel.