Cold runner
- Higher per part resin use
- Simpler maintenance on some layouts
- Easier material change on small presses
Glossary
What Is a Cold Runner? Injection Molding Explained
A cold runner freezes with each shot and is removed as trim or regrind feedstock.
Glossary
A cold runner solidifies with the part and is trimmed as scrap or regrind
Cold runner tools are often simpler for lower volumes or frequent material changes.
Plastic in the runner channel freezes each cycle and ejects as a slug or tab.
Scrap rate rises versus hot runner but capital cost is often lower.
Frequent material or color changes may favor cold runner simplicity.
Glossary
How cold runner 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.
Tradeoff
Cold runner versus hot runner on the same part
Volume and scrap math decide, not habit.
Hot runner
- Lower scrap at high cavitation
- Higher tool and service cost
- Longer purge on color change
Go deeper
Where this term connects
Each link is a different angle on the same program, not a duplicate definition.
Hot runner
Molten manifold between shots.
Hot runnerRunner
Channel geometry upstream of gates.
RunnerRegrind
Runner scrap feedstock.
RegrindGate
Entry after runner.
GateVisual 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
Cold runner questions
When is cold runner better?
Low volume, frequent material changes, or simple single cavity layouts often favor cold runners.
Is cold runner scrap quoted separately?
Material planning includes runner weight even if buyers count part weight only.
Can cold runners feed valve gates?
Valve gates usually sit on hot runner manifolds, not classic cold sprue only tools.
Next step
Upload volume for runner choice
CAD and annual volume help scope runner type on quotes.