Infill: Techniques for making more efficient FDM parts

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3D printed mold making process

Understanding Infill in FDM Printing

Printing strong, lightweight FDM parts in half the time.  

In this post, we'll delve into a critical aspect of FDM printing - infill. Understanding infill and choosing the right strategy is key to enhancing the quality and performance of your 3D prints.

3D printed master pattern

Closeup of a rectilinear (grid) infill pattern

What is Infill?

Infill refers to the internal structure of a 3D printed object. When designing a 3D model, it's not always necessary to print it with a solid interior. Instead, the interior can be partially filled with a repeating pattern, such as a honeycomb or grid-like structure. This technique maintains the object's strength and stability while reducing the overall material usage.

Fully self supporting pyramid

The range of infill densities

Why Infill Matters

When you 3D print an object, you have the option to choose its infill percentage, which determines the amount of material used to fill the interior. A solid, dense interior isn't always necessary, especially for large or non-functional prints. Printing a completely solid object would consume a significant amount of material and time, leading to increased costs and longer print durations.

This is where infill comes into play. By incorporating infill patterns, you can reduce material consumption while maintaining the structural integrity and strength of the printed object. The right infill strategy strikes a balance between different factors:


1. Strength and Durability


FDM printed objects with the right infill percentage exhibit improved strength and durability. This is particularly important for functional prototypes, mechanical parts, and load-bearing components. By providing internal support through infill, the printed parts can withstand the stresses and forces they may encounter during their intended use.


2. Weight Optimization


In certain applications, reducing the weight of the 3D printed object is crucial. Lighter objects can have advantages in areas such as aviation, automotive, and robotics, where weight directly impacts performance. By carefully choosing the infill percentage and pattern, you can remove excess material from non-critical areas, resulting in lighter and more efficient designs.


3. Material Efficiency


Effective infill strategies significantly reduce material consumption, which is particularly valuable when using expensive or specialty filaments. By printing with lower infill percentages or infill patterns optimized for material distribution, you can save costs and minimize material waste, making your 3D printing endeavors more environmentally friendly and economical.

Fully self supporting pyramid

Rendering of various infill types

Balancing Strength and Material Usage

The infill percentage determines the amount of material used to fill the interior of a 3D printed object. A higher infill percentage results in greater structural strength, while a lower percentage reduces material usage and creates lighter prints.


The choice of infill percentage depends on the object's purpose. For functional prototypes and parts requiring significant load-bearing capabilities, a higher infill percentage is recommended. On the other hand, decorative or display items can have lower infill percentages to reduce material consumption without compromising visual appearance.

SLA mold

Solid vs infill mechanical performance. 

Common Infill Patterns

FDM slicer software offers various infill patterns to achieve different mechanical properties. Let's explore some common infill patterns and their characteristics:


1. Rectilinear Infill (Grid Infill)


One of the simplest and most commonly used infill patterns. It consists of straight lines laid out in a grid formation, providing good structural support and versatility.


2. Triangular Infill


Composed of interconnected triangles, this pattern offers an excellent strength-to-weight ratio, making it ideal for parts that require high rigidity.


3. Honeycomb Infill


A repeating hexagonal pattern that strikes a balance between strength and material usage. It provides decent structural support while optimizing material distribution.


4. Gyroid Infill


A more complex pattern based on a mathematical algorithm, offering impressive strength and weight characteristics for lightweight, sturdy objects.

SLA mold

There are a huge variety of potential infill styles

Optimizing Infill for Your Projects

To achieve the best results for your 3D prints, optimizing the infill settings is essential. Here are some considerations to keep in mind:


1. Object Purpose and Design


Consider the function of your 3D printed object. If it is a functional prototype or a part meant to bear mechanical stress, higher infill percentages (e.g., 30% to 50%) are generally recommended. On the other hand, objects with low mechanical requirements or those designed for display purposes can have lower infill percentages (e.g., 10% to 20%).


2. Layer Height and Nozzle Size


The layer height and nozzle size used during printing influence how infill patterns are deposited. Finer layer heights and smaller nozzle sizes can accommodate more intricate infill patterns and result in smoother internal surfaces.


3. Slicer Software Capabilities


Different slicer software packages offer various infill patterns and the ability to customize infill density across different sections of the print. Explore these features to tailor infill settings to specific parts of your 3D models.


4. Balance Between Strength and Material Usage


Achieving the ideal balance between strength and material usage is a crucial aspect of infill optimization. Evaluate your project's requirements and aim for the highest infill percentage that meets the desired mechanical properties without excessive material consumption.

We'll handle it

At Forge Labs, we recognize that every 3D printing project is unique. Our experienced technicians work closely with you to understand the specific requirements of your parts. By leveraging our expertise in infill optimization, we can choose the most suitable infill strategy that aligns with your project goals and delivers exceptional results. From prototypes to end-use parts, we ensure that your 3D prints achieve the right balance between strength, weight, and material efficiency.


By embracing the significance of infill in FDM printing, you can elevate your 3D printing projects to new heights of quality and performance. Trust in Forge Labs' personalized approach to 3D printing, and let us help you turn your ideas into reality.