Snap Fit and Living Hinge Design for 3D Printing
1. Snap Fits
Snap fits are one of the most practical features in 3D printed parts — they eliminate the need for fasteners and allow easy assembly.
Best materials for snap fits:
Nylon (MJF) — Excellent, high flexibility and fatigue resistance
Tough Resin (SLA) — Good, designed for this purpose
PETG (FDM) — Good flexibility, doesn’t crack easily
ABS (FDM) — Moderate, can be brittle
PLA (FDM) — Poor, too brittle for repeated snapping
Design tips:
Deflection should not exceed 2–5% of the beam length
Add a radius at the base of the cantilever to reduce stress concentration
Include a lead-in angle (30–45°) for easy insertion
Design for print orientation — snap beams should flex parallel to layers, not across them (across-layer flex causes delamination)
Wall thickness of snap beam: 1.5–2.5mm for FDM, 0.8–1.5mm for SLA
2. Living Hinges
Living hinges are thin, flexible sections that allow two rigid parts to pivot.
Best materials:
Nylon PA11 (MJF) — Best choice, high elongation at break
Nylon PA12 () — Good, slightly less flexible than PA11
TPU (FDM) — Flexible material, good for thick living hinges
Polypropylene-like resins (SLA) — Designed for living hinges
Materials to avoid for living hinges:
- PLA, ABS, standard SLA resins — Too brittle, will crack
Design guidelines:
Hinge thickness: 0.8mm minimum for MJF Nylon, 0.8–1.0mm for FDM TPU
Length of hinge: minimum 3–5mm to distribute bending stress
Add a small radius on both sides of the hinge (not a sharp transition)
Orient so the hinge flexes parallel to print layers for MJF, and FGF
3. Testing
Always request a test print for parts with snap fits or living hinges. Material behavior and print settings significantly impact performance. Order a test print.