Machined metal baseline
- Tight tolerances familiar to machinists
- Heavy parts at scale
- Multiple ops and fasteners in assembly
DFM
Metal to Plastic Conversion: Injection Molding Design Rules
Metal to plastic conversion requires draft, coring, and ribs, not a direct copy of machined parts.
DFM
Metal to plastic conversion trades machining for molding DFM
Parts designed for CNC do not always map cleanly to molded geometry.
Plastic needs draft, uniform wall, and ribs instead of solid metal webs.
Assembly features molded in one shot can replace multiple machined brackets.
NetProto quotes one hardened steel tool for production programs when DFM accepts the conversion.
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.
Framing
Machined metal bracket versus molded equivalent
Conversion wins on piece price at volume when DFM is done early.
Molded plastic redesign
- Draft and coring required on CAD
- Stiffness from ribs and geometry
- Tooling amortized over production volume
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 articleDraft angle
Release rules plastics need.
Draft angleRib design
Stiffness after material change.
Rib designPlastic injection molding
NetProto production path.
Plastic injection 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
Conversion questions
Can plastic match metal strength?
Often partially. Load cases and FEA should be revisited.
Does conversion always need new CAD?
Yes. Translate function, do not copy metal geometry literally.
Will NetProto advise on material?
State load and environment. DFM review discusses resin families on qualified programs.
Next step
Upload conversion CAD with load notes
Include assembly context and critical mates on the quote upload.