A thin, flexible section that repeatedly bends to connect two rigid halves as a single printed part.
A living hinge stores elastic energy in a thin web rather than a separate pivot. Ideal thickness 0.3–0.6 mm, length 2–5 mm along the bend axis. Material choice is critical: PP and TPU survive >1 million cycles; PLA fails at <100 flexures. Orientation must place layer lines parallel to the hinge axis so layers do not peel apart.
FDM: orient hinge axis along Y so layers run parallel to the bend. Use PETG, TPU or PP. Minimum 2 perimeters on hinge section, 0% infill in the web. SLA: flexible resin grades enable sub-0.4 mm hinges. SLS: PA12 living hinges are durable but stiffer than FDM TPU.
Do not bend a freshly printed FDM hinge cold: flex it while still warm from the bed to pre-condition the layers. Avoid PLA for repeated-flex applications. Standard SLA resins are too brittle: always use a flexible grade. Over-sizing the web thickness eliminates the elastic function.
Related terms: Snap-fit design, Clearance for moving / mating parts, Joint orientation for load direction
| Theme | assembly |
|---|---|
| Also called | flexure hinge, integral hinge |
| Source | materials/flexible-resin.md, materials/elastomers.md |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert