What Is Infill Density (Percentage) in 3D Printing? (Detailed)

Learning the terminology is one of the most vital steps to master the 3D printing process, especially with many terms that sound similar but mean entirely different things.

As it’s easy to confuse some of the terms, getting a good grip of the terminology allows you to feel comfortable during the research and the printing process, making it easy to adjust the parameters that will take your print quality to the next level.

Today, we will be taking a deep dive into one of the most imperative terms in 3D printing, infill density, which impacts many vital factors such as print time, the amount of filament used, how strong the printed model is, and many more.

So, what is infill density (percentage) in 3D printing?

Infill density is a percentage value that determines the amount of plastic that fills the model you print.

As the infill density value gets bigger, the model becomes heavier and stronger due to the increased amount of plastic in it.

While infill density is one of the more straightforward terms to understand in the 3D printing world, taking a more detailed look at it will allow us to see how it really affects the printing process and the end product.

What Is Infill Density (Percentage) in 3D Printing?

At its core, infill density does not require more than a single sentence to explain.

In a nutshell, infill density refers to the amount of plastic inside a 3D printed model, where a value of 100% would mean that the model is full of plastic with no gaps inside, and 0% would mean that the model is entirely hollow.

By this logic, we can say that a higher infill density value means more plastic goes into the model, meaning the model becomes stronger and heavier as the infill density value increases.

On the other hand, the increased amount of plastic means that the printer requires more time and more filament to complete the printing process.

While not the only one, infill density is one of the primary parameters that determine how strong a 3D printed object will become, making it one of the most significant points of consideration before starting the printing process.

How Does Infill Density (Percentage) Affect the Strength of a Model?

Perhaps the most vital part about infill density is how it affects the strength of the 3D printed model, as it’s essentially the reason for choosing an optimized infill density value.

It is no secret that a higher infill density value increases the model’s strength, as an identical object with more substance in it will always be stronger than one with less.

On the other hand, as you may predict, the story doesn’t end here since there are a few nuances to be aware of about the relationship between infill density and strength.

Infill Density Does Not Increase Strength Linearly

The first thing to consider about infill density is that it doesn’t increase the model’s strength linearly.

For instance, a model with an infill density of 50% is nowhere near being twice as strong as a model with an infill density of 25% despite having twice as much plastic.

As a result, it’s often not favorable to use a too high infill density value due to the large amount of weight it adds to the model.

Infill Pattern Impacts the Strength of the Model

Infill density is not the only thing that affects the model’s strength, with the infill pattern also playing a significant role.

For instance, let’s compare a high strength pattern such as gyroid against low strength patterns such as lines and zig-zag.

As the structure of the gyroid pattern is much more durable, it can easily outperform patterns like lines and zig-zag in terms of strength even with lower amounts of infill density.

While the more complex (higher strength) patterns also increase the print time, they allow you to create more durable objects with less plastic.

Infill Gradient Impacts the Strength of the Model

Similar to the infill pattern, the infill gradient is another factor to keep in mind for the model’s strength.

In a nutshell, the infill gradient refers to the distribution of the infill within the model.

While this distribution is uniform by default, it’s possible to use a custom gradient to add a higher level of infill to the parts of the model that will experience stress.

By using a carefully created infill gradient, it’s possible to make an object more durable with a lower level of infill density, which shows us that a higher infill density doesn’t necessarily mean a higher level of strength unless both objects are identical.

What Is a Good Infill Density Value?

Finding a good infill density value isn’t always an easy task as it can show significant amounts of difference between different models, depending on their purpose.

Models, Figurines, Decorative Objects (Low Strength)

As models, figurines, and decorative objects are purely cosmetic – they are the group that requires the smallest amount of infill density and the least strong infill pattern.

We recommend using an infill density value between 0% and 20% for models, figurines, and decorative objects.

As for the infill pattern, a low-strength option such as lines, zig-zag, or rectilinear will give you the quickest print time.

As a 3D printed model with such a low infill density and weak infill pattern will be very prone to breakage, you need to be very careful with such models.

General Usage (Medium Strength)

The next category is general usage, which includes models you can expose to some degree of stress.

An item such as a key holder would fall into this category, where it would sustain a certain level of load, but not enough to consider it a functionally printed model.

For general usage 3D printed models, we recommend an infill density between 20% and 50%, depending on its exact use case.

Infill patterns such as grid, triangles, tri-hexagon, and honeycomb are suitable options, offering a balance between strength, print time, and filament usage.

While the models you print using this formula can tolerate a certain level of stress, carrying a load should not be the only purpose of the object in this case.

Functional Prints (High Strength)

Last but not least, let’s talk about functional prints, where the main attribute of the object is robustness.

We recommend an infill density between 50% and 100% for functional prints, once again depending on the exact use case.

High-strength infill patterns such as gyroid, octet, cubic, and cubic subdivision are the best options in this case, where print time and the amount of filament used will be the highest.

The primary purpose of a model you print with this formula should be to sustain loads, as such high infill density values for a model that won’t experience stress is overkill.

How to Set Infill Density in Cura?

Setting the infill density in Cura is a simple task which you can easily perform by following the steps we have outlined below:

  1. Click the Prepare tab on the top of the Cura window.
  2. Click the rightmost pane to bring up the Print Settings.
  3. Type “infill” into the search box to bring up all infill-related settings.
  4. Type the desired infill density value into the corresponding input.

Wrapping Up

Since the infill density value can easily make or break a 3D printed model, it’s an essential concept that every 3D printing enthusiast should fully understand.

To quickly recap, the infill density value determines the amount of plastic that goes into the model, directly impacting the amount of filament you use, the time you spend printing, and how heavy and resistant your model becomes.

While a simple concept at its core, correctly tuning the infill density value requires a decent amount of experience and knowledge, especially considering its relationship with the infill pattern setting.