Compared to most other manufacturing techniques, 3D printing must control the precision of two structures of the part: the outer wall and the filling. The outer wall, refers to the outermost area of the part, while the filler is whatever exists inside the part. Usually, the printer will have some level of control over the foreign currency, but the infill is more dynamic and plays a huge role in the strength, weight, structure, buoyancy, etc. of the part. In 3D printing, the user can define a number of parameters to control the type of infill used for the part.
Of all these parameters, two are the most important: infill density and infill pattern. Below, I'll walk you through "infill" through a few different fabrication methods to better understand how it works in 3D printing.
3D printing and traditional manufacturing
Infill 3D printing differs from other, more traditional manufacturing methods. Let's take injection molding and subtractive manufacturing as examples. Injection molding involves inserting material into a mold to form a part, and due to the very nature of the technology, controlling the internal structure is simply not possible. Therefore, injection molded parts are either solid or hollow (with gas injection molding), with nothing in between. Subtractive manufacturing, like CNC machining, requires cutting material. Similar to injection molding, the filling cannot be adjusted, so the interior is completely solid. But 3D printing can design any mass and make it layer by layer by extruding material.
Fill density can significantly affect material consumption
Fill density is the "fullness" inside the part. In the slicer, it is expressed as a percentage from 0 % to 100%, where 0% means partially hollow and 100% means completely solid. Fill density can greatly affect the weight of a part: the fuller the interior of a part, the heavier it will be. Besides weight, print time, material consumption, and buoyancy are also affected by infill density. The same is true for strength, although of course it is also related to many other factors such as material and floor height.
Some slicers also allow for different fill densities within the same part. This is called variable infill density, and a specific setting in the slicing program allows the user to specify any density variation desired for different areas of the print. So, what percentage of infill density should be used in actual printing?
●15-50% infill density is recommended for most "standard" prints that do not require extra strength. This density percentage reduces print time, saves material, and provides good strength.
●Functional prints need to be strong. Therefore, a higher infill is recommended: more than 50%. This setup takes longer to print and consumes more filament but results in a stronger part.
●For figurine models used for display purposes only, 0-15% infill density is recommended. This increases print speed and doesn't consume a lot of filament at all. Models printed in this density range will be very light, but not very strong.
Recommended settings
1. Standard printing: 15-50%
2. Functional printing: 50-100%
3. Figurines and model prints: 0-15%
4. Flexible printing: 1-100%
Fill pattern
A hatch pattern is the structure and shape of the material inside a part. From simple lines to more complex geometries, hatch patterns can affect a part's strength, weight, print time, and even flexibility. In different slicer programs, there are many different fill modes.
Like infill density, different infill patterns have different properties such as complexity, material efficiency, and the number of connection strength planes (2D or 3D). For example, a spiral pattern connects the outer walls in three dimensions, providing more overall strength. Therefore, this pattern takes up more material than patterns such as lines. So which fill pattern should you choose?
● Line: A line fill pattern consists of lines printed in one direction (along the X or Y axis) in every other layer. This infill pattern provides strength in only two dimensions, which is good for fast printing. Line patterns don't use much material and are light in weight.
●Honeycomb: As the name suggests, this pattern produces a honeycomb structure, creating an appealing visual effect. This infill pattern is suitable for semi-fast prints that require moderate strength and don't consume too much material.
Grid: A grid fill pattern is similar in appearance to lines, but instead of unidirectional lines every other layer, each layer contains two-dimensional lines with twice the space between the lines. This mode provides two-dimensional power but is still somewhat powerful. Grid patterns consume an average amount of material and take a medium amount of time to complete.
●Triangle: A triangular pattern looks like overlapping triangular lines that extend in three directions in the XY plane. This fill pattern only provides strength in two dimensions but is still suitable for prints that require strength.
● Three-way hexagon: A three-hexagon fill pattern consists of various lines extending in three directions in the XY plane, forming a hexagonal pattern with a triangle in the middle. This fill pattern provides two-dimensional strength, perfect for intense prints.
●Cubes: This mode produces stacked cubes, but because they are tilted 45 degrees around the X and Y axes, they look more like triangles at any moment. This pattern provides excellent strength in three dimensions but requires more material and time than other patterns.
● Octet: An octet fill pattern is similar to a cube pattern, but instead of adding slanted triangles, the pattern is materialized as a square. This fill pattern is a three-dimensional pattern that not only looks great but is also useful for parts that require strength.
●Spiral: Spiral fill patterns might look the coolest, but they're also arguably the weirdest fill patterns. It consists of a concave irregular curvature that ends up traversing the path. It is designed to achieve the best balance between strength, material, and printing time.
●Concentric: A concentric hatch pattern is an internal structure made up of concentric lines that match the outline of a part (ie its perimeter). This pattern can be printed quickly, is suitable for flexible parts, and consumes much less material than most patterns.
Recommended settings
1. Standard prints: grid or triangle
2. Functional printing: cube, helix, or octet
3. Figurines and Model Prints: Lines
4. Flexible printing: concentric
Summarize
In addition to patterns and densities, there are two other noteworthy categories of fill settings: variable settings and artistic patterns. Both allow you to be more creative with fill settings. Variable settings enable you to adjust infill density as the part progresses through layers. For example, if you want the bottom of a part to have 10% infill up to layer 30, then switch to 50% infill, the variable settings allow you to do this. What can be realized in software such as Simplify3D, PrusaSlicer, and Cura? Infill for art is a way to turn different fill patterns into works of art. This process looks great on earrings, pendants, and other jewelry and artwork.