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Assembly Feature Design: Injection Molding Design Rules
Assembly features molded into the part need snap, tolerance, and gate planning together.
DFM
Assembly features molded in reduce fasteners and labor
Snap hooks, alignment posts, and keyed slots belong on the DFM checklist.
Molded alignment features speed assembly but need tolerance stack review.
Snaps designed in one half may need lifters or side actions on the hook undercut.
Document intended assembly sequence so mold design supports degating and handling.
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 feature checklist
Bring these to DFM review.
Mate part CAD or key dimensions if available
Snap retention and deflection acceptance
Clearance slots for tolerance stack
Cosmetic faces that must stay clean for labels or seals
Related rules
Design guide
Jump to sibling rules before you freeze CAD.
DFM article
Long form engineer guide.
DFM articleCantilever snap fit
Snap beam design.
Cantilever snap fitTolerance stack up
Assembly clearance math.
Tolerance stack upOvermolding
Multi material assembly context.
OvermoldingVisual 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
Assembly feature questions
Can snaps be tuned on T1?
Minor steel safe moves only. Beam geometry sets deflection.
Do assembly features affect gate choice?
Yes when weld lines cross snap roots.
Should I provide mate part CAD?
Yes when clearance stacks matter for release.
Next step
Upload assembly CAD stack
Include mate parts or envelope models with molded alignment features.