Infill is the internal lattice a slicer generates inside a 3D-printed part, set as a density percentage from hollow to solid to balance strength, weight, material use, and print time.
Infill is the repeating internal structure that fills the hollow interior of a 📝3D Printing model, distinct from the solid outer walls and the top and bottom layers. It is controlled in the slicer as a density percentage, ranging from 0% (a hollow shell) to 100% (a fully solid part), and directly governs a part's strength, weight, material consumption, and print duration.
Higher infill density generally increases stiffness and load-bearing capacity, but the relationship is non-linear: gains taper sharply above roughly 50%, where additional material adds substantial weight and time for negligible strength. Most functional prints use densities between 20% and 40%, which yield a favorable strength-to-weight ratio without excessive filament use or long print times.
The infill pattern — the geometry of the internal lattice — is chosen independently of density. Grid and rectilinear patterns intersect straight lines for fast, general-purpose fills, while gyroid and honeycomb patterns distribute material more evenly across multiple directions, favoring isotropic strength or flexibility. Pattern and density together determine how a part responds to compression, impact, and directional load.