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All DFM topics on one route.
Design guide hubDFM
Runner Design: Injection Molding Design Rules
Runner design balances fill across cavities and ties to gate location on your part.
DFM
Runner layout sets fill balance on multi cavity tools
Part design still drives where the runner can live on the parting line.
Runner size and layout affect how evenly each cavity fills and packs.
Cold runners add regrind. Hot runners add capital and tip maintenance.
Asymmetric parts may need adjusted runner lengths even when cavities look identical.
DFM
Quote this rule with your CAD upload
NetProto DFM review flags these geometry patterns before steel is ordered.
- Call out draw direction and cosmetic faces on the model.
- Note resin family even when the grade is not final.
- Tighten tolerances only on mating features that need them.
Multi cavity
Runner inputs for DFM
Share cavitation assumptions early.
Cavity count target or range for quoting
Known cosmetic face on each impression
Material regrind policy if cold runner
Balanced fill priority versus shortest runner volume
Related rules
Design guide
Jump to sibling rules before you freeze CAD.
DFM article
Long form engineer guide.
DFM articleCold slug wells
Runner end traps.
Cold slug wellsRunner glossary
Shared terms.
Runner glossaryFamily molding
Shared mold programs.
Family moldingVisual reference
Molding context for this rule
Images from the Forge media library illustrate typical programs.
Injection molded part design review on CAD
Injection molded part design review on CAD
Plastic housing with ribs and bosses
Plastic housing with ribs and bosses
Engineer measuring molded component
Engineer measuring molded component
FAQ
Runner questions
Can buyers design the runner?
Part and gate location constrain runners. Mold designer details steel.
Do runners affect warp?
Indirectly through fill balance and orientation.
Will runner scrap appear on the quote?
Resin usage includes runner mass on cold runner tools.
Next step
Upload cavitation context with CAD
Note cavity count goals and cosmetic faces for runner planning.