The model behind the numbers
A printed part is a solid shell (walls, top and bottom) around a lattice core. The shell is approximated as surface area × wall thickness. For the core we use the Gibson–Ashby scaling for cellular solids: relative strength ≈ (relative density)n. Stretch-dominated 3D patterns like gyroid, cubic and triangles are close to n = 1; bending-dominated patterns like lines are closer to n = 1.5–2.
strength ≈ (shell + core × infilln) ÷ volume × 100
These are relative estimates for comparison, not engineering values — layer adhesion, orientation and material dominate real strength. Test critical parts.
Practical takeaways
Adding walls is usually the cheapest strength: going from 2 to 4 perimeters often beats doubling infill. Above ~40% infill, returns per gram fall for most patterns. For decorative parts 10–15% is enough; for functional parts 25–40% gyroid or cubic with 3–4 walls is a common choice.
FAQ
Does more infill make a print stronger?
Yes, but with diminishing returns per gram. Walls carry most bending load, so extra perimeters often add more strength than extra infill.
What is the strongest infill pattern?
For all-direction strength, gyroid and cubic are excellent. Grid and lines can be strong in one direction but weaker in others.
What infill should I use for functional parts?
25–40% gyroid or cubic with 3–4 walls is a good starting point. Use 100% only for small, highly loaded parts.
How accurate is this strength estimate?
It's a relative comparison based on cellular-solid scaling, useful for choosing settings, not for safety-critical design.
Recommended gear
- PETG filament, 1 kg — Tougher and more heat-resistant than PLA for functional parts.
- Digital calipers (150 mm) — Essential for tolerances, flow calibration and checking prints.
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