Infill Patterns and Density

This lesson covers the settings. For what infill is and why parts are not printed solid, start with Infill Fundamentals.

Where the settings are called what

What it controls	PrusaSlicer	OrcaSlicer	Bambu Studio	Cura
How much infill	Fill density	Sparse infill density	Not confirmed	Infill Density (or Infill Line Distance)
Shape of the infill	Fill pattern	Sparse Infill Pattern	Sparse infill pattern, in Process, Strength	Infill Pattern
Thicker infill layers to save time	Combine infill every X layers, Automatic infill combination	Infill Combination	Not confirmed	Infill Layer Thickness
How far infill reaches into the walls	Not confirmed	Infill Wall Overlap	Not confirmed	Infill Overlap

Not confirmed means we did not find the name in that slicer's documentation; the feature may still exist.

Density

Which way it pushes: UltiMaker's infill guide says higher density gives a stronger part and a smoother, better-supported top surface, and costs material, weight and time.

How much: Rule of thumb Prusa's infill article says most models print well at 10 to 15 percent and that values above 30 percent are rarely needed. It also says strength is mostly defined by perimeters, not infill, though infill helps with resistance to crushing. So for a weak part, add walls first and raise density second.

At 100 percent: PrusaSlicer switches the pattern to rectilinear automatically, and Bambu Lab lists only a few patterns (Concentric, Rectilinear, Aligned Rectilinear, Hilbert Curve, Archimedean Chords and Octagram Spiral) as supporting 100 percent. UltiMaker recommends straight-line or non-overlapping patterns above 80 percent.

Densities are not directly comparable between patterns: OrcaSlicer notes that patterns do not all count density the same way, so the same percentage can use different amounts of plastic.

Patterns, by job

Pattern	What the makers say about it	Use it for
Rectilinear, Lines	One line direction per layer, alternating. Prusa: among the fastest, saves filament, no build-up at crossings. UltiMaker: weak, but good top-surface support.	Display parts, fast prints
Grid	Both directions in every layer. Prusa: more solid than rectilinear, but plastic builds up where lines cross, which can cause noise and occasionally a failed print. Bambu Lab warns of nozzle scraping at high speed.	General parts on slower printers
Triangles, Tri-hexagon	Bambu Lab: good shear resistance and even horizontal strength, but needs extra top layers and the crossings hinder flow at high density.	Parts loaded sideways
Cubic	Bambu Lab: fairly even strength in X, Y and Z. UltiMaker: reduced pillowing.	Functional parts
Gyroid	No crossings within a layer. Prusa: strong in all directions and saves material. Bambu Lab and UltiMaker: slower to slice and larger G-code files; Bambu Lab notes vibration at high density and speed.	Functional parts, parts loaded in several directions. UltiMaker notes it is not very stiff and lists it as good for flexible models.
Honeycomb	Prusa and Bambu Lab: strong, but about 25 percent more material, and Prusa says it can take up to twice as long.	When stiffness matters more than time
Adaptive cubic	Dense near walls, top and bottom, sparse in the middle. Prusa: about a quarter less material than rectilinear while keeping good top support.	Large hollow volumes
Lightning	Supports only the top surfaces. UltiMaker: saves a lot of material but adds no strength. Bambu Lab: for decorative models only.	Figures and display models
Concentric	Follows the walls inward. Prusa: useful for transparent or flexible parts, but slow. Bambu Lab: weak against sideways loads.	Flexible filament, clear prints

UltiMaker warns that self-crossing patterns (Triangles, Grid, Tri-Hexagon, and to a lesser degree Cubic and Octet) cause material build-up, nozzle collisions and vibration. If you hear the nozzle ticking across the infill on a fast printer, try a pattern without crossings before slowing everything down.

Time savers

• Combining infill layers. The slicer prints infill once every two or three layers at double or triple thickness while walls keep the fine layer height. Prusa's example: three 0.1 mm layers become one 0.3 mm infill layer, and the nozzle diameter caps it at about 80 percent of the nozzle, roughly 0.32 mm for a 0.4 mm nozzle Maker spec.
• Gradual or adaptive density. Cura's Gradual Infill Steps halves the density in steps lower in the part. UltiMaker says it weakens the part, so use it for visual models only.
• Lightning or Support cubic for parts that only need their top surfaces held up.

Infill and wall overlap

Infill has to bond to the innermost wall. More overlap bonds better, but UltiMaker notes the infill may then show through the outer wall. Starting point OrcaSlicer suggests around 10 to 15 percent to avoid over-extrusion and rough surfaces. Leave it at your profile's value unless you see gaps between infill and walls, or infill marks on the outside.

What to change first

1. Part breaks: add walls, then raise density. Change pattern last.
2. Top surface sags or shows gaps: add top layers first; raising density also helps.
3. Print too slow or too heavy: lower density, switch to adaptive cubic or lightning on display parts, or combine infill layers.
4. Nozzle ticks or scrapes on infill: switch from a crossing pattern (grid, triangles) to one without crossings.