Plastic components often fail in manufacturing because the CAD model ignores the realities of injection molding. Good injection molding design balances strength, appearance, tooling and cycle time.
Keep Wall Thickness Consistent
Large changes in wall thickness can cause uneven cooling and defects such as sink marks or warpage. Where possible, design transitions gradually.
Use Ribs for Stiffness
Ribs can increase stiffness without making the entire component thick. Avoid making ribs excessively thick relative to the surrounding wall because thick sections can increase the risk of sink marks.
Boss Design
Bosses are commonly used for screws, inserts and locating features. They should be supported appropriately and designed with manufacturing access in mind.
Add Draft Angles
Draft angle helps the molded part release from the tool. The required amount depends on material, surface texture, depth and tooling conditions.
Use Fillets
Sharp internal corners can create stress concentrations and tooling difficulties. Fillets also support smoother material flow and better part durability.
Think About the Parting Line
The mold parting line affects appearance, ejection and tool complexity. Design important surfaces and features with the likely tooling direction in mind.
Avoid Unnecessary Undercuts
Undercuts can require slides, lifters or other tooling mechanisms. If an undercut is not functionally necessary, redesigning the geometry may reduce tool complexity.
DFM Review Before Tooling
Before releasing a plastic part for tooling, review wall thickness, ribs, bosses, draft, parting line, ejection, inserts and critical dimensions. Early injection molding DFM review is much cheaper than correcting a mold after manufacturing.