How to Define Infill in 3D Printing

Infill is an essential concept in FDM 3D printing that directly impacts the strength, appearance, and structural integrity of a part. If you are new to 3D printing or looking to refine your designs, understanding and optimizing infill can make a significant difference in the quality of your prints. In this post, we will define infill, explain its importance, and share insights specifically related to FDM 3D printing technology based on our professional experience.

What is Infill in 3D Printing

Infill refers to the internal structure of a 3D-printed part, which is created as the printer builds layers inside the outer shell. It is not visible from the outside but plays a critical role in determining the part's strength, weight, and material usage. The percentage of infill describes how dense the internal structure is, ranging from hollow (0 percent infill) to completely solid (100 percent infill). Infill can be customized with various patterns, such as grid, honeycomb, or triangular, depending on the desired characteristics of the final part.

How Infill Affects Strength and Appearance

The primary function of infill is to provide strength and support to a printed part, but it also influences other factors, such as material shrinkage and surface quality resulting from it. These effects should be carefully considered when designing a 3D model or setting up a print. For functional FDM parts, optimizing infill settings is crucial to balancing strength, material usage, and overall performance.

1. Impact on Strength

   
   

   A higher infill percentage results in stronger parts that can withstand greater loads and forces. For example, 100 percent infill is sometimes chosen for functional parts that need maximum durability, such as mechanical components, despite the fact that other factors like material shrinkage and surface quality may have a significant influence on the result.

   
   

2. Effect on Surface Quality

   
   

   Infill settings can also affect the appearance of a part. Higher infill percentages can exacerbate material shrinkage during cooling, leading to surface imperfections or visible distortions. This is especially noticeable with large parts or geometrically complex designs where uneven cooling can result in warping, gaps, or layer separation.

   
   

3. Balance Between Strength and Appearance

   
   

   Achieving the right balance between strength and surface quality often requires experimentation. If the goal is to create a visually appealing part, a lower infill percentage, such as 15 percent, is typically sufficient. For applications where both strength and appearance are important, a moderate percentage like 20 to 50 percent can be a good starting point.

   
   

When 100 Percent Infill Is Actually Used

Although a completely solid infill might seem like the best way to ensure maximum strength, it is rarely the default choice. Using 100 percent infill leads to higher material consumption and longer printing times. Additionally, it can introduce issues with material shrinkage, resulting in uneven surfaces or geometric distortions.

In some cases, customers specifically request 100 percent infill for durability, if it aligns with the part's purpose. We may remind customers about potential compromises in the final surface quality due to the density of the material.

For most applications, reducing the infill percentage while maintaining adequate strength provides a more efficient solution without sacrificing the overall functionality or quality of the part.

Factors That Influence the Right Infill Percentage

Selecting the right infill percentage depends on the part's purpose, size, material, and design complexity. Here are a few key factors to consider:

1. Part Functionality

   
   

   Functional parts that will bear weight or endure stress, such as brackets or mechanical components, typically require higher infill percentages. However, for decorative or aesthetic parts, a lower percentage is usually sufficient.

   
   

2. Geometry and Size

   
   

   Large parts or designs with complex geometries are more prone to warping or cracking if infill is too high. Uneven cooling can create internal stresses that lead to imperfections. For these cases, balancing infill density can help minimize shrinkage and improve stability.

   
   

3. Material Properties

   
   

   The type of material being used plays a significant role in infill selection. Some materials, like PLA, are less prone to shrinkage, while others, such as ABS, require careful handling to prevent warping. For more guidance on optimizing your designs, check out our guide on how to create 3D models for printing.

   
   

4. Aesthetic Requirements

   
   

   If the surface finish is a priority, such as in display models or prototypes, lower infill percentages help minimize visible distortions. Experimenting with percentages around 15 to 20 percent can achieve an optimal balance between appearance and structural integrity.

   
   

Optimizing Infill for Batch Production

When producing parts in larger quantities, consistency is key. Small variations in infill settings can affect the quality of the final products, making experimentation and testing even more important. By refining infill settings during prototyping, you can ensure that every part in the batch meets the required standards for strength, appearance, and material efficiency.

How to choose the right percentage of infill

Infill plays an important role in the success of FDM 3D-printed parts. From its impact on strength and surface quality to the importance of finding the right percentage for specific applications, it is a parameter that demands attention and expertise. Whether you are designing prototypes, functional parts, or aesthetic models, understanding what infill means and how to define infill will help you achieve better results. If you need assistance with your custom 3d printed parts, we are here to guide you through the process and ensure your designs are optimized for success.