What is Infill in 3D Printing?

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What is Infill in 3D Printing?

Infill is one of the key parameters you can change when you’re slicing your CAD model to create a 3D print. It affects the strength, rigidity, weight, feel, appearance, and cost of your print.

So, it must be pretty important, right?! If you want to get the most from your 3D prints, it’s really worthwhile learning what infill is and how you can change it to get the best 3D prints.

Luckily, you’re in the right place as in this article, I’ll take you through a comprehensive guide on what infill is, the different types, and its benefits. 

What Is Infill?

One of the major benefits of 3D printed objects is that they don’t need to be completely solid. This means you are able to save on material usage and the time to print.

However, it’s most usually not possible for a 3D printed object to be completely hollow either as they would be too weak and likely to bend or break.

This is where infill comes in. Infill is the internal structure of a 3D printed object.

Infill literally ‘fills in’ the void inside your print.

Your 3D printing slicer software will have a default infill, and you can choose from other types depending on your needs.

Infill Density

The main parameter that you change on your infill is the density. The infill density refers to the quantity of filament printed inside a 3D object, which directly relates to its printing duration, weight, and strength.

You can choose the infill density to range from 0% to 100%, with the latter being an entirely solid object, whereas the former is a hollow object. 

As infill density increases, the printed object will become more robust but also heavier and take longer to print.

Benefits of Using an Infill 

If you don’t need an infill, then you shouldn’t use one. However, there are many benefits to using infill, such as…

Strengthening Your 3D Print 

If you are printing an object which requires additional strength such as a plinth or weight-bearing bracket, there is a good chance you’ll need to use an infill. Failure to use adequate infill may result in your prints breaking when subjected to their design load, and then you end up using more filament reprinting.

When printing parts that will be put to practical use, you should use a high infill percentage. This means that the infill percentage needs to be 20% or more to create a durable part that will withstand loading.  

Guarantee Quality of Your 3D Prints 

Some 3D objects need additional internal support even whilst they are printing. This is important because the infill ensures the print quality is not compromised.

For example, when designing a model with numerous interior overhangs which cannot be printed over by your 3D printer, infills are deemed necessary. This is because infill gives your model the support it needs while new layers are added on top.  

What Infill Parameters Can You Change? 

There are two parameters you should be concerned about when thinking of infills. These are percentages and patterns. Let me explain which each one does…

Infill Percentage 

The infill percentage determines the amount of filament to be used, the strength of the final product, and how long the printing will take. This value lies between 0 and 100. In most slicer software such as CURA, the default infill percentage is set between 18 and 20%. However, you can adjust these settings depending on the desired strength of the final 3D print. 

Infill Patterns 

The pattern you choose for an infill directly influences the cross-sectional appearance of the final print. Integrated into slicer software are pre-established infill patterns. Some designs are widespread; thus, they come pre-installed in every slicer software. 

Very popular infill patterns include the triangular, honeycomb, wiggle, and grid or rectangular pattern. These different patterns have a unique combination of flexibility, strength, and filament savings.   

What Are the Different Types of Infill? 

There are numerous types of infills you can choose from the best way for me to explain them to you is to give some examples of how you would use them.

Infill for Models and Miniature Figurines

3D prints intended to be used as either figurines or models do not need to be very robust, with the infill density ranging from 0% to 15%. The reason for this is that they usually are not placed under lots of pressure or subjected to a lot of heavy handling, and as they are relatively small, the strength of the walls is usually enough on its own. The most preferred infill patterns in this instance are the zig-zag or lines as they are faster to print. 

These two patterns generate a 2D grid, with each layer having a single axis. With the zig-zag infill pattern, you get one continuous line, whereas with the line infill pattern produces several lines for every layer. 

For 3D prints such as porotypes, figures, or models that do not get exposed to tremendous pressure, these simple infill patterns are ideal. 

Standard 3D Prints 

If you are planning to print 3D models with medium strength and more resistance to pressure, using a higher infill density of 15% to 50% is recommended. The higher the infill percentage, the longer it will take to print, so it’s a good idea to start low and experiment. The infill patterns under this category are; 

  • Triangles: This is also referred to as the diagonal infill and should be used when you want to strengthen the print walls. With this infill pattern, it is possible to achieve greater strength since the lines forming the pattern produce force at an angle of 45 degrees. 
  • Grid: Most FDM 3D printers come with this 2D pattern as the default infill pattern. It is a functional infill pattern because it generates strength in every direction, whereas it remains fast to print. 
  • Tri-hexagons: This infill pattern is also known as the honeycomb or hexagonal infill. As in nature, this is an efficient shape, with high strength compared to its volume. Like the rectangular infill, it also generates strength in every direction, but the printing takes longer to complete as the printhead as to change direction more often. Furthermore, this infill pattern has a more efficient shape, making it sturdier while still using less filament. 

Functional 3D Prints 

These infill patterns are ideal when designing practical 3D prints that need to have strength is several directions. This would include DIY projects, auto parts, brackets, bridges, etc. The infill density of these 3D prints is usually higher than 50%, and it includes patterns such as; 

  • Cubic: This pattern consists of tilted and stacked cubes and is a perfect choice for perfecting your 3D printing skills. 
  • Octet: It is a pattern that incorporates stacks of pyramid shapes and offers adequate strength in every direction. 
  • Cubic subdivision: This is a slight variation of the cubic 3D pattern as it features tiny cubes inside the 3D object. As a result, every direction gets provided with strength while still using less filament. 
  • Gyroid: This 3D pattern resembles waves and is an excellent choice for an object that will be stressed in numerous ways. It is also robust in numerous directions. 
  • Quarter cubic: This infill pattern slightly resembles the octet, and its only difference being its pyramid shapes are moved with regards to the other half. It is an excellent pattern as it provides strength throughout the whole 3D model. 

Flexible 3D Prints 

Infill on flexible prints is an interesting topic as it has a great effect on just how flexible your final print it. Infill in flexible materials allows you to fine-tune just how much and in what direction your print flexes.

The infill density of this infill pattern varies between 0% to 100%, and the selected percentage depends on how “spongy” the final 3D print needs to be. Some of the infill patterns for flexible materials include; 

  • Cross: This 2D pattern has spaces between the grids and crosses, which allow for twisting and bending. Furthermore, this infill pattern has grids that resemble imaginary crosses. 
  • Cross 3D: This infill pattern has a slight difference to the cross in that the lines start moving at inclines the more the print grows. As a result, it results in a 3D object that is more rigid and sturdier. 

Which is the Best CURA Infill? 

CURA is the most popular 3D printing slicer, and it comes with a number of built-in infill patterns. In fact, it has so many, it can be hard to decide which one you should use!

Whereas every type of infill has its advantages and disadvantages, the one CURA infill that stands out from the rest is the honeycomb or hexagon infill. The reason for this is that this infill ensures the efficient use of the filament while still guaranteeing a robust build quality. 

The honeycomb pattern is prevalent in nature and engineering, and bees instinctively know that this is the ideal combination that offers a perfect balance between material use and strength. It is for this reason too that 3D experts opt for this as the preferred infill. Furthermore, this pattern does not only save you time and the filament but also evenly distributes strength in every direction. 

Nevertheless, the honeycomb pattern requires the print head to make plenty of direction changes, a challenge you will have to deal with, especially when using bulky print heads. This can result in slower print speed and a messier print. Despite this downside, this infill pattern remains the go-to pattern among many 3D professionals. 


After reading this article, you now understand what an infill is and the vital role it plays in 3D printing. You also know of the different types of infill patterns to choose from, each providing you with a different combination of strength, filament savings, and flexibility. With this in mind, you will have an easier time choosing an infill that best meets your needs. 

I hope this article has answered all your questions about 3D printing infill, but if you have any more questions, don’t hesitate to drop me a comment below, and I’ll do my best to answer!

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