Mechanical Joints
Reference library of mechanical joint types for plastic parts — snap-fits, press-fits, hinges, and interlocking joints with design guidelines for FDM 3D printing.
Engineering3D PrintingManufacturingDesign
A collection of mechanical joint types commonly used in plastic part design. Each article covers how the joint works, when to use it, key design parameters, FDM printing considerations, and common failure modes.
Design resources
- “Snap-Fit Joints for Plastics” — Bayer/Covestro (free PDF, the industry standard reference)
- “Designing Plastic Parts for Assembly” by Paul Tres (Hanser)
- CNC Kitchen (YouTube) — FDM-specific mechanical testing
Map
- Annular Snap Fit A circular snap-fit where a ring or lip deflects over a mating cylinder — used for caps, lids, and cylindrical enclosures.
- Cantilever Snap Fit The most common snap-fit type — a flexible beam with a hook that deflects during assembly and locks behind a mating surface.
- Dovetail Joint A trapezoidal interlocking slide joint — strong, self-aligning, and easy to print for sliding connections and rail systems.
- Living Hinge A thin flexible section that acts as a hinge — one piece, no assembly, but material choice and print orientation are critical.
- Press Fit An interference fit where a shaft or pin is forced into a slightly undersized hole — simple, permanent, no moving parts.
- Torsion Snap Fit A snap-fit that uses twisting deflection instead of bending — higher strain capacity and more compact than cantilever designs.