Single cavity first tool
- Lower upfront tooling before volume proves out
- Simpler fill balance tuning
- Common when geometry is large or cosmetic risk is high
Glossary
What Is a Mold Cavity? Injection Molding Explained
The cavity half shapes the outside of the part and often carries Class A surfaces.
Glossary
The cavity is the mold half that shapes the outside of your part
Cosmetic faces often live on the cavity side, so steel and polish matter here.
In a two plate tool, the cavity half forms exterior surfaces customers see and touch. The core half forms interiors, ribs, and bosses.
Multi cavity tools duplicate the same cavity geometry to multiply parts per cycle. Family tools instead combine unlike parts in one mold base when volumes justify shared tooling.
Cavity steel choice balances polish retention, wear at the gate, and repairability over program life.
Glossary
How cavity 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.
Design
What to show when cavity side cosmetics matter
These callouts reduce rework between DFM and texture samples.
Class A surface identification on the CAD model
Texture spec or SPI finish target if already selected
Parting line location relative to visible edges
Draft direction tied to the cavity pull
Layout
Single cavity versus multi cavity
Cavity count is a capital versus piece price trade, not a free multiplier.
Multi cavity production
- Lower piece price when annual volume absorbs tooling
- Requires balanced runners and consistent cooling
- DFM must justify ejection and venting for every impression
Go deeper
Where this term connects
Each link is a different angle on the same program, not a duplicate definition.
Core
Interior geometry, ribs, and ejection land here.
CoreA side and B side
Which half mounts to which platen.
A side and B sideFamily molding capability
Unlike parts sharing one mold program.
Family molding capabilityVisual 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
Cavity questions
Is the cavity always the A side?
Shops often call the cavity the A side, but always confirm on the tool design print.
Can cavities be swapped as inserts?
Insert cavities are common when only one region of the tool changes between revisions.
Does cavity polish equal final part gloss?
Steel polish sets the ceiling. Texture, resin, and pack also shape what you see.
Next step
Plan cavity cosmetics in DFM
Upload CAD with visible faces marked before steel is cut.