Molded in insert
- Insert loaded each cycle or with automation
- Strong retention when knurl and boss are sized right
- Tooling must protect insert during fill
DFM
Molded In Inserts: Injection Molding Design Rules
Molded in inserts need retention features and mold shutoff planned before steel.
DFM
Molded in inserts load the tool during fill
Brass or metal inserts placed in the mold before shot see plastic pressure and shutoff steel.
Insert location must survive fill without shifting. Retention knurls or undercuts hold the insert after demold.
Insert molding differs from post mold press in cycle and automation planning.
NetProto insert programs quote when insert type, count, and tolerances are defined on CAD.
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.
Assembly
Molded in insert versus post mold press
Both can work. Tooling and cycle differ.
Post mold insert
- Mold may stay simpler without insert shutoffs
- Secondary station adds labor and handling
- Good when insert count is low or geometry is awkward in mold
Related rules
Design guide
Jump to sibling rules before you freeze CAD.
Design guide hub
All DFM topics on one route.
Design guide hubDFM article
Long form engineer guide.
DFM articleInsert retention
Knurl and undercut features.
Insert retentionPost mold inserts
Secondary insert path.
Post mold insertsInsert molding services
NetProto capability page.
Insert molding servicesVisual 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
Molded in insert questions
Who supplies inserts?
State vendor part numbers on the RFQ when known.
Can inserts be added after T1?
Sometimes with steel change. Design for insert before cut is cheaper.
Do inserts affect warp?
Metal in the part changes local shrink and stiffness.
Next step
Upload insert locations on CAD
Include insert vendor data and retention features for DFM.