Updated: Oct 18, 2021
What is Infill in 3D Printing:-
Infill is basically internal structure of the 3D print. 3D printing allows careful control of two mutually exclusive yet exhaustive aspects: exterior walls (or perimeters) and infill. The walls, however thick, form the outermost regions of the part, while the infill is whatever exists within them. Though one does have some control over the walls, the infill is far more dynamic and plays an enormous role during a part’s strength, weight, structure, buoyancy, and more. In 3D printing, you have the flexibility to define various parameters that govern the infill used for an element. These parameters are set during a slicer program (Like Cura, Prusa, etc) when a 3D model is translated into G-code instructions. The most important of those parameters fall into two fundamental aspects: infill density and infill pattern. We’ll re-examine the fundamentals of those aspects during this article as a number of the foremost common densities and patterns.
But first, let’s examine “infill” across a pair of various manufacturing methods to understand higher how it works in 3D printing.
Density of 3D Printing:-
The infill density defines the amount of plastic used on the inside of the print. A higher infill density means that there is more plastic on the inside of your print, leading to a stronger object. An infill density around 20% is used for models with a visual purpose, higher densities can be used for end-use parts.
Infill density is the “fullness” of the inside of a part. In slicers, this is usually defined as a percentage between 0 and 100, with 0% making a part hollow and 100%, completely solid. As you can imagine, this greatly impacts a part’s weight: The fuller the interior of a part, the heavier it is.
Besides weight, print time, material consumption, and buoyancy are also impacted by infill density. So, too, is strength, albeit in combination with many other elements such as material and layer height.
Some slicers also allow for different infill densities within the same part. This is known as variable infill density, and specific settings in the slicing program allow you to specify any density changes you want for different areas of your print. We’ll return to this topic a little later.
Types of Infill in 3D Printing:-
Rectilinear is one of the basic infill patterns. It creates a rectilinear grid by printing one layer in one direction, the next layer rotated by 90°, etc. This way, it saves filament and doesn’t accumulate material at crossings . It’s one of the fastest printed infills. This type of infill is the only one recommended for 100% infill printing.
This infill is formed by parallel lines drawn inside the model, which resemble the outside support structures. Similar to the previous type, this infill saves time, has average material consumption, plus it doesn’t accumulate material at crossings.
This is one of the simplest and fastest variants of infill. Unlike rectilinear, it’s printed in both directions (rotated by 90°) in each layer. This way, material accumulates in spots where the paths cross. The grid infill is more solid (and has better layer adhesion) than the rectilinear infil.
This infill works similarly to the grid infill – the paths cross in one layer, however, this time they are printed in three directions and form a triangle structure. Material and time consumption is almost identical to the grid.
The Stars infill is based on triangles but paths are shifted to make six-pointed stars. Again, this infill is created by lines that cross each other within a single layer. Material and time consumption is similar to the previous infill.
Again, this is an infill with paths that cross each other within one layer. However, unlike previously described infills, it creates cubes oriented with one corner facing down. This way it makes numerous air pockets that might serve as heat insulation, or cause the object to float on water (with waterproof filaments such as PETG).
The Line is one of the infills that don’t feature any crossing paths in one layer. Its paths are similar to the rectilinear infill but they are not parallel to each other. Instead, they are printed at an acute angle. Unsurprisingly, this infill is similar to rectilinear when it comes to printing time and material consumption.
The concentric infill traces the model perimeter lines and makes them smaller towards the center. In other words: if you print a cylinder, the concentric infill will create concentric circles inside that cylinder. This can be useful with transparent parts or flexible models
This infill prints a grid made of hexagons. Its main advantage is mechanical resistance and optimal paths without crossings. The main disadvantages are higher material consumption (approx. 25% more) compared to other infills, and print time that can take up to twice the time of previously described options.
3D honeycomb prints bigger and smaller squares and octagons to create columns of periodically increasing and decreasing thickness. Again, this infill doesn’t have crossing lines in one layer, however, due to the way it lays down the paths, it creates small gaps between layers. Material consumption and print time are slightly worse compared to the regular honeycomb pattern.
The Hilbert curve creates a rectangular labyrinth inside the model. The main advantage of this infill is its non-traditional look, plus it can be pretty easily filled with epoxy resin or another liquid
This spiral-twisted infill allows easier filling with liquid. This simple shape saves material and time (compared to the rectilinear infill). Similar to the concentric infill, the Archimedean chords help with model flexibility if you print it with flexible filament.