Infill patterns & density
Infill is the structure inside your part — the stuff between the walls that gives a print strength without making it solid. Pick the right pattern and density and your part is strong, light, and fast to print. Pick wrong and you waste hours of print time on infill that does nothing for you. This is the working comparison.
15% gyroid for general-purpose prints (strong in every direction, prints fast). 10% lightning for decorative pieces (fastest, lightest, but only supports the top shell). 30% cubic or gyroid for functional/mechanical parts. Above 50% infill almost never adds useful strength — thicker walls do that better.
How infill actually works
Infill is not what holds your part together — walls do that. Infill mostly does three things: supports the top layers so they don't sag (pillowing); transmits load between top and bottom shells; and resists localised crushing. Beyond 30–40% infill density, returns diminish sharply because walls dominate the load path. For maximum strength per gram, increase wall count before infill density.
The patterns — what each one is good at
Grid
Two perpendicular sets of straight lines. The default in many slicers. Prints fast, decent strength in two axes (X and Y), weak in the third (Z). Notable downside: the nozzle has to plow through the previous line at every intersection, causing artifacts.
- Strength: medium (anisotropic).
- Print time: fast.
- Use for: default OK for general purpose; not the best at anything.
Lines / rectilinear
One set of straight lines per layer, alternating direction every layer. Simpler than grid, slightly faster, similar strength.
- Strength: medium.
- Print time: fast.
- Use for: when grid's intersection bumps are showing through.
Triangle
Three sets of lines forming triangles. Stronger than grid (triangles are rigid shapes), but slower to print because of all the direction changes.
- Strength: high in the layer plane.
- Print time: medium.
- Use for: parts loaded primarily sideways (in the X/Y plane).
Cubic
3D cubes oriented diagonally. Strong in all three axes (the only common pattern that's truly 3D-strong from each layer), fast to print, looks neat in preview.
- Strength: high and isotropic (strong in every direction).
- Print time: medium.
- Use for: functional parts loaded from multiple directions.
Gyroid
A 3D continuous curved surface inspired by molecular structures. Excellent strength-to-weight ratio, isotropic (strong in every direction), prints with no sharp direction changes — meaning fast travel-free toolpaths.
- Strength: high and isotropic.
- Print time: fast (smooth curves = continuous extrusion).
- Use for: PrintPal's recommended default. Combines speed and strength.
- Bonus: beautiful at low densities (5–10%) for translucent vase-mode-style prints.
Honeycomb / Hexagonal
Classic honeycomb cells. Strong, but slow because of the many vertices.
- Strength: high in the layer plane; weak in Z.
- Print time: slow.
- Use for: parts where the layer-plane stiffness matters most; structural panels.
Lightning
Branching tree-like structure that only exists where it's needed to support the top layers. Uses dramatically less material than other patterns.
- Strength: low in everything except supporting the top shell.
- Print time: very fast.
- Filament use: lowest of any pattern.
- Use for: decorative parts, display models, prototypes you'll throw away. Not for mechanical parts.
Concentric
Concentric copies of the part outline. Smooth, decorative, used most for top/bottom layers rather than internal infill. Inside, weak.
Adaptive cubic
Cubic where density adjusts dynamically — dense near the surface, sparse in the middle. Saves material on large parts without sacrificing the top-layer support.
Density — what percentage do you actually need?
| Density | Use for | What it does |
|---|---|---|
| 0% | Vase mode, hollow shells | Single-wall print; very fragile |
| 5–10% | Decorative, display, tall vases | Just enough to support top shell with lightning |
| 15% | General-purpose default | Good strength for everyday prints, fast |
| 20–25% | Functional but not load-bearing | Stronger; tools, fixtures, brackets |
| 30–40% | Mechanical parts under load | Strong; combine with 5+ walls |
| 50%+ | Rarely justified | Returns diminish; thicker walls give more strength per gram |
| 100% | Solid plastic parts | Slow, heavy; sometimes needed for very small features |
Pattern comparison at a glance
| Pattern | Speed | Strength | Material use | Isotropic? |
|---|---|---|---|---|
| Lightning | Fastest | Low | Lowest | No |
| Lines | Fast | Medium | Medium | No |
| Grid | Fast | Medium | Medium | No |
| Gyroid | Fast | High | Medium | Yes |
| Cubic | Medium | High | Medium | Yes |
| Triangle | Medium | High | Medium | No |
| Honeycomb | Slow | High in plane | Medium | No |
| Concentric | Fast | Low | Medium | No |
| Adaptive cubic | Fast | High | Low | Yes |
Practical tips
- Walls before infill. If a part isn't strong enough, increase wall count first. 5 walls + 15% gyroid > 3 walls + 50% grid, weight for weight.
- Infill orientation matters. If you can, orient the print so the layer plane (X/Y) bears the load — FDM parts are ~30% weaker in Z.
- Bridges over infill. Top layers bridging across infill voids can sag with low density. Either increase density or enable "bridge over infill" smoothing in PrusaSlicer/OrcaSlicer.
- Infill line width > perimeter line width (e.g., 0.6 infill, 0.42 perimeter on a 0.4 nozzle). Faster and no quality cost.
- Infill speed > perimeter speed. Infill quality doesn't show; print it fast.
- Infill anchor (PrusaSlicer/OrcaSlicer): connects infill to walls so the walls don't separate. Default values work; just leave enabled.
Related articles
Sources & further reading
- CNC Kitchen — Stefan Hermann's infill strength tests
- Prusa Knowledge Base — Infill patterns
- Bambu Lab Wiki — Infill density and patterns