Infill Percentage and Patterns: What to Use and Why
Contents
3D printed parts are mostly not solid inside. Between the outer walls, a sparse skeleton is printed, just dense enough to support the part. This skeleton is called infill. In most cases 10–15% infill is enough for display parts, 15–25% for everyday parts and 30–50% for load-bearing parts. For strength, the number of walls is often more important than infill.
What does infill percentage mean?
Infill percentage shows how much of the inner volume is filled with plastic. 0% means hollow and 100% means completely solid. As the percentage goes up:
- The part gets heavier and stiffer.
- Print time and material use increase.
- Beyond a certain point, the gain in strength slows down.
Recommended percentages
| Use | Infill | Note |
|---|---|---|
| Figures, models, decorative | 5–15% | With enough top layers the surface stays smooth |
| General parts, boxes, organizers | 15–25% | A balance of strength and time |
| Functional parts, brackets | 25–40% | Also increase the wall count |
| High load, screw hole areas | 40–60% | Increasing wall count first is more efficient |
| Fully solid | 100% | Rarely needed, adds internal stress and warping |
Wall count is usually more important
The outer walls carry most of the forces on a part. So to increase strength, adding walls (perimeters) first is more efficient than adding infill.
- Display parts: 2 walls.
- General use: 3 walls.
- Functional parts: 4–6 walls.
On a 0.4 mm nozzle, 3 walls means about 1.2 mm of wall thickness. Around screw holes, 3–4 walls make the area around the hole almost solid and improve screw grip.
Infill patterns
| Pattern | Trait | When |
|---|---|---|
| Lines | Very fast, strong in one direction | Quick prototypes |
| Grid | Simple and fast, nozzle can bump at crossings | General |
| Triangles | Good strength under side loads | Parts with flat surfaces |
| Cubic | Balanced strength in every direction | General and functional |
| Gyroid | Equal strength in every direction, fluid shape | Functional, TPU, aesthetic |
| Honeycomb | Good strength, slow | Parts that need strength |
| Lightning | Supports only the top surface, very fast | Display parts |
| Concentric | Follows the outer shape | Flexible parts |
Gyroid
Gyroid is a repeating wavy surface. Its strength is nearly equal in every direction, the nozzle does not run into its own lines between layers and it prints fast. For many people it is the best general-purpose pattern. It also gives even flexibility in flexible TPU parts.
Lightning
Lightning prints only as much infill as is needed to support the top surface. It saves a lot of material and time on display parts, but leaves the inside of the part almost empty. Do not use it on load-bearing parts.
Infill and the top surface
If the infill percentage is very low, the top layers have to bridge over gaps and holes appear on the top surface. In that case, increasing the top layer count is often better than increasing infill. There is a separate article on this: Top surface holes.
Advanced infill settings
- Gradual infill: Raises the infill percentage gradually from bottom to top. The top surface is supported while total material goes down. Available in Cura.
- Adaptive cubic infill: Concentrates infill only in areas near surfaces and leaves the interior sparse.
- Infill layer thickness: Some slicers print infill only every second layer to shorten the time. It is a sensible saving for the interior you cannot see.
- Infill overlap: Sets how much the infill joins the walls. It is kept around 10–25%. If it is too low, the infill separates from the wall.
- Modifier regions: In PrusaSlicer, OrcaSlicer and Cura you can assign different infill to a specific region only. For example, 60% infill only around a screw hole.
Infill and warping
Dense infill makes the plastic shrink more as it cools and lets the part build up more stress. With materials like ABS, using needlessly high infill raises the warping risk.
Does 100% infill make the strongest part?
Most of the time yes, but the material and time cost is very high and internal stress goes up. In most cases 5–6 walls and 40–50% infill give similar strength in much less time.
Which pattern prints fastest?
Lines and lightning are fastest. Gyroid also prints fast and gives balanced strength, so it is a good middle ground.