Cold runner
Solidified runner scrap each cycle.
Cold runnerGlossary
What Is a Hot Runner? Injection Molding Explained
A hot runner system keeps plastic molten in channels between the barrel and cavity gates.
Glossary
A hot runner keeps plastic molten in the manifold between shots
Hot runners cut runner scrap but add tool cost, maintenance, and process sensitivity.
Manifold heaters maintain melt path from barrel to gate on many multi cavity tools.
Color changes take longer when hot runner volume must purge.
Tooling scope in the quote defines runner type when it affects piece price.
Economics
When hot runner payback is realistic
Volume and cavitation usually decide, not preference alone.
- High annual volume with stable resin and color
- Multi cavity layouts where cold runner scrap dominates material cost
- Large parts where runner weight rivals part weight
Go deeper
Where this term connects
Each link is a different angle on the same program, not a duplicate definition.
Valve gate
Timed shutoff on hot drops.
Valve gateMold base
Manifold plates integrate with base stack.
Mold baseRegrind
Less runner regrind on hot runner programs.
RegrindVisual 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
Hot runner questions
Does NetProto use hot runners?
Runner type appears in tooling scope when it affects your quote.
Do hot runners eliminate gate vestige?
Gate style still leaves witness. Valve gates can reduce blush.
Are hot runners harder to troubleshoot?
They add temperature and balance variables versus cold runner.
Next step
Clarify runner scope on RFQ
Upload CAD and volume notes for piece price with the right runner plan.