3D Printing Infill: Patterns & Densities for Stronger Prints

3D printing has revolutionized how parts are designed, prototyped, and produced. One key aspect of 3D printing that plays a significant role in determining a printed object’s strength, weight, and structure is the 3D printing infill.

In this article, we will discuss what infill is and highlight its important features.

What is 3D Printing Infill?

3D printing infill refers to the internal structure of your 3D printed part.

You’ll rarely print a solid 3D model. Instead, most 3D prints are printed mostly hollow with an interior structure called infill.

3D printing infill is used to provide structure to your printed part. Infill provides support to internal overhangs and gives 3D-printed parts enhanced tensile strength and durability.

Printing a 100% solid part would use a lot of material, resulting in high costs and printing times. Infill allows parts to maintain strength while reducing their material usage, price, and print time.

There are two primary components to 3D printing infill: density and pattern.

Infill density refers to the amount of plastic inside a print. An infill density of 100% is a solid object, whereas 0% is a hollow object.

Infill pattern refers to the internal structure of the 3D printed part. Different shapes provide different strength characteristics to printed objects.

You’ll notice that different designs offer different advantages as you experiment with different infill patterns and densities. For example, a honeycomb pattern provides excellent tensile strength using less material, whereas a rectilinear design is quicker to print.

When working on a 3D printing project, consider the purpose of your model and the desired mechanical properties. Mechanical components subject to a reasonable degree of wear and tear require higher infill densities and stronger types of infill patterns.

Decorative items aren’t subject to the same load requirements. You can use lower infill densities and faster printing patterns when producing decor items.

Infill Density

Infill density refers to the amount of plastic inside a 3D-printed model. A value of 100% means the model is completely filled with no gaps, while 0% creates a hollow model.

As you start 3D printing, selecting the correct infill percentage is vital for achieving your model’s desired functionality and appearance. I find a medium strength infill pattern of 10% and 30% is optimal for most printing applications.

This range of infill density offers a balance between strength, filament consumption, and printing time.

Here are some suggested infill percentages for various applications:

• Decorative prints (0-15%): Ideal for lightweight miniatures, display models, and objects that don’t need much structural integrity.
• Standard prints (15-30%): A good choice for objects requiring more strength but not needing to be solid or too heavy.
• Durable prints (30-50%): Suitable for functional parts that undergo moderate repeated stress, where tensile strength and durability are important factors.
• Functional prints (50-100%): Best for solid functional items and components that must withstand significant forces. Remember that a 100% infill might reduce flexibility in certain models.

Infill Patterns

The infill pattern of a 3D-printed part refers to its internal structure. Infill patterns use different shapes, offering various strength, weight, flexibility, and print speed characteristics.

Different slicing software offers different 3D printing infill patterns.

Lines

Lines consist of parallel lines printed along either the X-axis or Y-axis. Lines are one of the fastest infill patterns to print, are lightweight, and don’t use much filament.

The biggest drawback is that line patterns only provide strength in two dimensions. They’re best used for non-structural and non-functional prints for decorative applications.

Grid

The grid pattern consists of simple crisscrossing lines, creating a series of small squares within the interior of your print. The grid pattern balances print speed and strength, making it suitable for a wide range of applications.

Grid patterns provide two-dimensional strength but are far more durable than line patterns.

I use the grid pattern for cosmetic models that don’t need to be strong. Grid infill patterns provide enough support to my models, print relatively quickly, and don’t use much filament.

Honeycomb

As the name suggests, the honeycomb pattern resembles the structure of a beehive. The honeycomb infill pattern consists of hexagonal cells. This pattern provides an excellent combination of strength, rigidity, and weight savings.

Due to the nature of hexagonal shapes, stress is evenly distributed, resulting in better mechanical properties overall.

The pattern is also visually appealing to watch as your printer creates layer upon layer.

If you plan to use the hexagon infill pattern, orient your model so that the loading would occur in the X and Y direction and not the Z direction, as the design only provides two-dimensional support.

Triangular

The triangular infill pattern consists of equilateral triangles arranged tightly together. Like the honeycomb pattern, triangular infill provides isotropic mechanical properties, as stress is distributed uniformly throughout the print.

This pattern is ideal for parts requiring flexibility and strength. However, triangular infill shapes take longer to print and use more filament than simpler patterns like grids or lines.

Again, like the honeycomb pattern, I choose to make sure that the loading is always directed in the X and Y section of the part because it is stronger in X and Y and not very strong in the Z-axis.

Cubic

Cubic infill involves a three-dimensional lattice of cubes inside your print. The cubes are printed at a 45-degree angle and appear more like triangles than the grid pattern.

The Cub pattern’s unique advantage is its isotropic mechanical properties, rendering your print strong in all three directions.

The increased complexity of the Cubic infill means that print times are longer.

Cubic Subdivision

Cubic Subdivision infill patterns are a smarter version of the previous cubic pattern. The cubic subdivision infill uses less material, resulting in faster print times without sacrificing strength.

The pattern achieves lower filament usage by creating internal cubes of different sizes. The largest cube is in the center of the print, and they get smaller towards the interior walls of the model.

Because of the complexity of generating the support structures, the cubic subdivision infill has longer slicing times. However, we think it’s worth it in exchange for faster printing speeds.

Quarter Cubic

The Quarter Cubic infill pattern uses tetrahedrons to produce a strong infill that can withstand heavy loads.

I recommend using a quarter cubic infill for small parts that require strength characteristics. But avoid using this infill pattern on cosmetic pieces, as the bridging distance can affect the surface quality of the printed part.

Zig Zag

Zig-zag infill is similar to lines, except the infill runs in a zig-zag pattern. Like lines, zig-zag infill is quick to print, but it’s not very strong, only providing strength in two dimensions.

You should only use zig-zag infill on decorative pieces.

Lightning

Unlike the other3Dd printing infill patterns on this list, a lightning infill is specifically designed to provide support to internal structures that require extra support during printing. The infill resembles lightning bolts or something closer to Cura’s tree supports.

Lightning infill doesn’t provide much strength to parts, but it is one of the fastest internal support structures to print because it only provides infill support where required.

Cross

The cross pattern uses a series of crosses to create a more flexible support structure. However, the orientation of crosses facing along the Z-axis makes this infill more flexible along the X- and Y-directions.

Cross 3D

The cross 3D pattern improves upon the previous pattern by providing flexibility in all directions. However, due to the pattern’s complexity, it takes longer to slice models. 

Gyroid

The gyroid pattern is a complex, three-dimensional wave-like structure with one of the strongest 3D printing infill patterns, optimizing print speed and filament usage. Unlike many other 3D printing infill patterns, the Gyroid pattern offers isotropic mechanical properties, meaning you can expect the part to behave the same regardless of the direction of the load.

With isotropic strength and flexibility, the gyroid pattern is ideal for parts requiring even stress distribution and structural integrity. However, due to its intricate nature, printing with a gyroid infill takes longer than using simpler patterns.

I always use a gyroid infill when printing a part exposed to repeated inconsistent loads and stresses. I find that the Gyroid Infill offers the best strength-to-weight ratio of all the infill structures.

Octet

Cura’s Octet infill pattern comprises tetrahedrons and cubes, creating a kaleidoscope-like appearance. Octet is a strong infill best used for mechanical parts, as it can impact the surface quality of a print.

Concentric

The concentric infill pattern consists of concentric loops that follow the shape of your print’s outer walls. This pattern provides a visually appealing finish, particularly in transparent or translucent materials.

The concentric pattern isn’t ideal for mechanical parts requiring high strength or rigidity. However, concentric infill is a great option when appearance is your primary concern because it has a low impact on the surface finish of your printed object.

Which Infill Pattern is Best?

To achieve the best results for your 3D printing projects, we suggest following these infill settings when using Cura:

Start by selecting an infill pattern that best suits your project’s needs.

• Standard prints: Grid, Triangles, or Honeycomb.
• Functional prints: Cubic, Gyroid, or Cubic Subdivision.
• Decorative prints: Lines, Lightning, or Grid.
• Flexible prints: Cross 3D, Cross, or Concentric

Remember to consider your infill pattern in conjunction with your infill density.

Infill Overlap

Lastly, adjust the Infill Overlap Percentage to ensure proper bonding between the infill and outer walls. An infill overlap of 10-15% is sufficient for most prints.

The Infill Overlap Percentage is the percent of the inner wall contour in direct contact with the infill material. Finding the right balance of overlap is essential.

Too much contact, and you may see some over-extrusion errors and surface imperfections. Too little overlap, and your infill won’t provide the required strength.

Frequently Asked Questions