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The Strongest Infill Patterns | All3DP

Excerpt

Slicers offer many infill pattern options, but not all of them yield strong 3D prints. Read on to learn about the strongest infill patterns!

To evaluate which infill pattern yields the strongest parts, there are a couple of important considerations we should discuss. The first is the directional strength of an infill pattern, and the second is the type of strength measured in testing.

Directional Strength

Not all patterns provide the same strength across all three axes (X, Y, Z), and many are more suited towards certain planes. For example, the grid pattern offers great strength along the Z-axis (perpendicular to layer lines) but is weaker throughout the XY-plane (parallel to layer lines). To get the most out of patterns that are strongest along certain axes, consider orienting your model so that the part of the print that needs to be strong is aligned with the axis along which the infill pattern is strongest.

There are also 3D patterns that provide strength more balanced across the three axes. As a tradeoff, the individual axis strength is reduced. For example, the gyroid infill pattern provides mostly balanced strength in all three directions, but it’s not the strongest pattern along the Z-axis.

Types of Strength

The second important consideration is the type of strength measured in testing an infill pattern. In this article, we’ll present the most common infill patterns and their performance in two strength tests: elongation and compression. The former involves applying force at the two ends of a sample to pull it apart, while the latter is the inward application of force on a sample, essentially squishing it until it breaks.

Both tests are valid ways of determining the strength of an infill pattern and are quantified in terms of the force a sample can take before it fails, but they inform us about different use cases. In the real world, parts are often subjected to a combination of tensile and compression stresses at the same time.

Consider holding a rod at each end and bending it to snap it in half. The outer face is in tension as the ends get pulled away from each other, forming cracks in the surface. Meanwhile, the inner half gets compressed, forcing material out of the newly developed crease.

Tensile

The elongation test gives us an estimate of tensile strength, which can inform us about a part’s resistance to stresses that try to stretch it. This type of strength is essential to know for applications like buckles and clips.

The standard tensile strength test is conducted using dogbone-shaped samples and places stress on only one axis. As we established, 3D printed samples are anisotropic, meaning their strength will not be the same in all directions. Pulling the Z direction requires enough force to cause layer delamination, which is much less force than what’s needed to break each filament layer when pulling in the XY direction. In these tests, pulling is done in the XY direction.

Compression

A compression test indicates how well a part resists inward force and should be considered for load-bearing applications, such as shelf brackets.

A standard compression strength test uses strip-shaped samples that are held vertically between two parallel plates and squished. Just like for tensile tests, the compression strength of 3D printed parts is anisotropic, but the degree to which is more heavily influenced by the infill pattern and how effective it is at distributing stresses internally. Testing should be done in both the XY and Z directions for a full picture of a pattern’s performance.