What Is Infill in 3D Printing

Common Infill Patterns and Their Pros & Cons

Beyond just how much infill you use, the pattern or shape of the infill also matters. Slicer software offers many infill patterns (geometry of the internal lattice), and each pattern has advantages and disadvantages in terms of strength distribution, print speed, and stability. Here we compare five common infill patterns – Grid, Triangular, Honeycomb, Cubic, and Gyroid – highlighting their pros and cons for 3D printing:

Grid Infill

The Grid pattern consists of two sets of straight lines crossing at right angles, forming a square grid inside each layer. It’s one of the simplest and fastest infill patterns to print. Grid provides decent support in the vertical direction and good bonding between layers at the crossing points. Pros: Grid is easy to generate and prints relatively quickly; the intersecting lines each layer give it better in-plane stiffness than a single-line pattern, improving support for top surfaces. Cons: The strength is somewhat directional – grid infill is strong along the two grid axes, but it doesn’t reinforce diagonal or off-axis loads as well as more complex patterns. Also, because the paths cross each other in every layer, plastic tends to accumulate at the intersections; this can cause the printer nozzle to bump over the lumps, sometimes making noise or even leading to print defects if the nozzle catches. In summary, Grid infill is a good general-purpose choice for speed and simplicity, but it may not provide uniform strength in all directions and can introduce minor print artifacts at the cross points.

Triangular Infill (Triangles)

Triangular infill (sometimes just called Triangles) creates a network of interconnected triangles. In each layer, lines are laid in three directions (typically 0°, 60°, 120°), forming a triangular lattice. This pattern offers an excellent strength-to-weight ratio, as triangles are inherently rigid shapes. The triangular infill excels at withstanding compressive loads and shear forces from multiple directions. Pros: Very strong and rigid in-plane – the triangles resist deformation and provide robust support, making this pattern great for parts that need to endure heavy loads or direct pressure. The load is distributed through the triangular geometry, giving consistent strength across the layer. Cons: Triangular infill prints with a similar effort as grid (since lines still cross within each layer), so print time and material usage are about on par with a grid pattern. It doesn’t print quite as fast as simpler line infills, and like grid, the multi-directional crossings can lead to slight bumps at intersections (though triangles tend to distribute material more evenly). While triangles provide strength in-plane, they are still a 2D layer pattern – so purely vertical strength depends on layers bonding (unlike some 3D patterns). Overall, triangle infill is a go-to for strong, stiff parts, offering better multidirectional support than grid, at the cost of only modestly more print time.

Honeycomb Infill (Hexagonal)

Figure: A 3D print cross-section with honeycomb infill – a hexagonal cell pattern inspired by natural honeycombs. This infill provides excellent rigidity and evenly distributed strength.

The Honeycomb pattern uses hexagon-shaped cells tessellated throughout the infill. It’s visually recognizable as a bee’s honeycomb structure. Honeycomb infill is popular because it offers an excellent balance of strength and weight – hexagons are one of the most efficient shapes for filling space with minimal material while still providing strength. The pattern distributes load evenly in every direction within the plane, resulting in high mechanical stability and often a very solid feel to the part. Pros: Strong in all directions – the hexagonal grid has no weak axis, giving isotropic in-plane strength. It supports top layers uniformly and resists shear and compressive forces well. Honeycomb also has a great strength-to-weight ratio; it provides a lot of rigidity without completely filling the space, which is why it’s used in aerospace and automotive parts where weight reduction is critical. Cons: The efficiency in strength comes at a cost of complexity – honeycomb infill typically takes longer to print than simpler patterns, because the printer is constantly changing direction to form the hexagons. Studies have noted it can use about ~25% more material and nearly double the print time compared to a grid or rectilinear infill of equivalent density. In practice, honeycomb infill can also put more computational load on the slicer. For most hobbyist prints, these downsides just mean honeycomb is chosen when maximum strength is needed and a bit of extra print time/material is acceptable. It remains one of the strongest infill patterns available, ideal for functional parts that need durability in every direction, but it’s usually overkill for quick prints or simple models.

Cubic Infill

Cubic infill is a three-dimensional infill pattern, meaning its structure extends and aligns over multiple layers to form a 3D lattice of cubes (often oriented with a cube corner pointing downward within the print). In each layer, cubic infill typically appears as a set of lines crossing, similar to a triangle or grid pattern, but over several layers those lines shift to create a repeating cube-like cell internally. The result is a pattern that provides support in X, Y, and Z directions, not just within one layer. Pros: Cubic infill yields uniform strength in all directions (an isotropic internal grid) because the cubes spread loads in 3D. This makes it excellent for structural parts that experience forces from many angles. It also has a good strength-to-weight efficiency — by creating diagonal supports through the volume, it can support weight with less material than a 100% solid fill. In fact, the air pockets in cubic infill can have interesting side benefits: they can improve thermal insulation, and if a part is made watertight, the trapped air can even make it float (as noted with some PETG prints). Print time and filament usage for standard cubic infill are usually comparable to grid or triangle infill, so it’s quite efficient. Cons: Because cubic is a repeating 3D pattern, it can sometimes be less dense near the center of a print than at the perimeters (which is generally good for saving material, but means pure cubic infill might leave large internal gaps if used at low densities). Some slicers offer “adaptive cubic” infill that increases density near surfaces for this reason. For very small models, cubic infill’s 3D nature might not have space to fully develop the lattice structure, so simpler patterns could be more practical at small scale. Overall, cubic infill is a strong choice for large, functional prints where you want solidity in all dimensions without going fully solid – it provides excellent all-around support.

Gyroid Infill

Figure: Gyroid infill inside a print. The gyroid’s wavy, continuous surfaces form a unique 3D lattice that offers uniform support in every direction and a visually intriguing pattern.

The Gyroid infill pattern is a relatively newer and highly regarded infill type, known for its distinct wave-like, undulating surfaces. Unlike straight-line based infills, gyroid creates a continuous 3D labyrinthine structure – essentially a series of curving surfaces that weave through the interior. This complex geometry gives gyroid infill some exceptional properties. Pros: Gyroid infill provides near-isotropic strength, meaning the part has almost uniform strength in X, Y, and Z directions. There are no straight-line weak planes; its continuous nature resists shear and torsion very well. It also has an excellent strength-to-weight ratio, similar to honeycomb or better, because it efficiently uses material to support stress in every direction. Another big advantage is that the gyroid pattern is continuous and self-supporting: it doesn’t require the print head to stop and start lines frequently or make sharp corners. The smooth curves mean the printer can lay down infill in one continuous path per layer, which minimizes retractions and crossing points that could blob – this often allows gyroid to print fairly fast and cleanly. The resulting infill also looks stunning and can be beneficial if you plan to encapsulate the part with resin or need internal channels – gyroid’s interconnected channels can allow fluids or air to pass through (useful in certain applications like filters or lightweight structures). Cons: Gyroid infill’s complexity can be slightly more demanding to slice and visualize. However, from a printing standpoint it has few downsides – it does not have the problematic crossing lines in a layer, and it provides excellent support for top layers. One potential consideration is that for maximum stiffness in one axis (say pure vertical compression), a pattern like aligned rectilinear or triangles might pack more material directly under load, whereas gyroid spreads it out; in other words, gyroid is very balanced, though not always the absolute strongest in one specific direction compared to a pattern tailored for that direction. In practice, gyroid infill is an outstanding choice for functional parts that see forces from multiple angles (e.g. tooling jigs, structural brackets) and has become a favorite in the community for its balance of strength, weight, and print reliability.

Summary of Pattern Pros/Cons: To choose an infill pattern, consider what your part needs. If you want fast printing and simplicity, a Grid or Lines (rectilinear) pattern might suffice. For maximum planar strength, Triangles or Honeycomb give very stiff support. For balanced, all-direction strength, 3D patterns like Gyroid or Cubic shine. Keep in mind that more complex patterns (honeycomb, gyroid) can improve strength but may increase print time, whereas simpler patterns (grid, lines) are quicker but less optimized in strength distribution. It often helps to experiment with different patterns for your specific model and requirements.

Infill Density: Low vs High Fill Percentages

Infill density (expressed as a percentage from 0% to 100%) determines how much of the interior volume is filled with material. This has a huge impact on strength, weight, and print duration. Here are some general guidelines for different infill percentage ranges and when to use them:

• 0–15% (Very Low Density/Hollow): These infill levels produce very lightweight parts with minimal internal support. Use infill in this range for pure display models, decorative pieces, or quick prototypes where strength isn’t important. For example, a cosplay prop or an architectural model might only need 10% infill or less – just enough to support the top layers and keep the shape. The part will be light and print fast, but also relatively fragile. (At the extreme, 0% infill is completely hollow – this is rarely used except for vase mode prints or shapes that can structurally support themselves with just outer walls.)

• 15–50% (Medium Density): This covers the typical infill percentages for general-purpose prints and moderately functional parts. Around 20% infill is a common default for many slicer profiles because it provides a decent balance of added strength without too much weight or time. In the 30–40% range, parts become significantly stronger and more rigid – suitable for prototypes that will be handled or minor functional use. Use 15–50% infill for things like product prototypes, hobby gadgets, or parts that need to be sturdy but not max-strength. This middle range strikes a balance: it improves strength and support notably over very low infill, yet keeps print time and material usage reasonable.

• 50–100% (High Density/Solid): High infill percentages are reserved for functional parts that require maximum strength, stiffness, or weight. Infill above ~50% starts approaching a nearly solid object, dramatically increasing strength and load-bearing capability. For example, a mechanical part that will bear weight, a tool handle, or a piece that will be drilled or screwed into might use 60%, 80%, even up to 100% infill. The part will be much heavier and take longer to print with these settings, but it will have a solid internal structure to withstand stress. Use high infill when the part’s function demands it – e.g., an engineering prototype under load or a replacement part for a machine. Note: Going all the way to 100% (completely solid) usually yields only a small strength increase beyond, say, 80-90%, because the part may already behave almost solid. Often, you can get near the same strength with slightly less than 100% infill, especially if you also increase wall perimeters. Fully solid infill is uncommon unless you truly need no internal voids or maximum mass.

Keep in mind there are diminishing returns in strength as you approach very high densities. A part at 50% infill might be, for example, 80% as strong as a fully solid part in many cases, but will print much faster and use only half the material. Each jump in infill density above that gives smaller and smaller gains in strength while linearly increasing material and time. Therefore, it’s wise to use just enough infill for your needs: low for lightweight objects, medium for ordinary use, and high for critical-strength parts.

Also, consider that infill density isn’t the only factor – the number of perimeter walls and the infill pattern also affect strength. Sometimes using a stronger pattern (like triangles or gyroid) allows you to achieve the needed strength with a slightly lower infill percentage. Some slicers even allow variable infill (different densities in different regions of a part) or gradual infill that increases density near top layers for support. These advanced techniques can further optimize strength vs. material, though they are beyond the basics of infill percentage.

Recommendations Based on Part Function

Choosing the right infill settings comes down to the intended use of your print. Here are some recommendations aligning infill choices with the function of the part:

• Display Models & Visual Prototypes: For models that are meant to be decorative, visual, or not subject to stress (figurines, concept models, cosplay props), use low infill. Something in the 5–15% range is usually plenty to support the outer shell and top layers. You can even print many purely visual objects nearly hollow to save time. Use a simple, fast pattern like Lines (rectilinear) or Lightning infill if using Cura. The Lightning infill pattern in Ultimaker Cura, for example, is designed specifically to minimize material: it creates a sparse, branching internal support only where needed for the top surfaces. This can reduce print times significantly for aesthetic pieces. The trade-off is that the part will not withstand much force – but that’s okay for a display piece. In short, for non-functional models: sparse infill, fast pattern, fewer walls. You’ll get a quicker, cheaper print and lower weight, and the object will still look fine externally.

• Functional Parts & Mechanical Components: If the printed part needs to handle stress, support weight, or serve a practical purpose (for instance, a tool, a replacement machine part, a drone frame, etc.), lean toward higher infill and stronger patterns. Typically, at least 25-40% infill would be recommended for moderately functional parts, and 50% or more for parts that must be very strong or rigid. Use infill patterns known for strength: Triangular or Honeycomb infill for maximum rigidity, or Gyroid/Cubic for a more uniform strength distribution. These patterns will ensure the part doesn’t have a single weak axis. Also consider increasing the number of perimeter walls for critical parts, since shells contribute a lot to strength. For example, a small mechanical bracket might be printed with 4 perimeter walls and 50% gyroid infill to make it tough. The downside is increased print time and material, but functional prints often justify it. Aim for the highest infill that still gives you an acceptable print time. Many functional prints work well in the 30-60% infill range with the right pattern, only going to very dense infill if absolutely needed (like parts that will be drilled into or experience continuous heavy loads).

• Balanced Use (Prototypes or Semi-Functional): Many prints fall in between – they need to be somewhat strong but not carry maximum loads. In these cases, a mid-range infill (20–40%) with a balanced pattern is a good strategy. For example, printing a gadget enclosure or a toy: you want it to be sturdy enough to handle handling but you also want to print it in a reasonable time. Something like 20% grid or cubic infill might suffice. If a prototype will undergo testing, perhaps bump to ~30% infill and use triangles or gyroid to avoid weak points. This gives you confidence the part won’t fail in normal use, without the overhead of a near-solid print. You can always iterate and increase infill if a prototype proves too weak. Remember that you can also reinforce specific areas (with modifier settings in advanced slicers) rather than making the whole part solid.

Finally, always consider the design and material of your part. Very thin or small parts might not benefit from high infill since there’s little room for infill anyway (in such cases, adding walls or ribs in the model might be more effective). And different materials respond to infill differently – for instance, a flexible TPU part with 20% infill will be quite flexible, while the same part in PLA might be sufficiently stiff even at 20% due to material properties.

Slicer Settings and Terminology (Cura vs. PrusaSlicer and Others)

It’s worth noting that infill patterns and settings can go by different names in different slicer programs. The core concepts are the same, but if you use various slicing software, you’ll see some terminology differences:

• For example, what PrusaSlicer calls “Rectilinear” infill is essentially the same as the “Lines” pattern in Cura – a back-and-forth line infill printed in one direction per layer. Both create a similar linear grid by alternating direction each layer (or at set angles), providing fast and simple infill.

• The pattern we described as Honeycomb (hexagons) might be labeled as “Tri-Hexagon” in Ultimaker Cura. Cura’s Tri-hexagon infill is a hybrid of triangles and hexagons but in effect serves the same purpose: a strong infill with hexagonal structure for stability. It combines three-directional lines to form a repeating hexagon and triangle tessellation.

• Some slicers offer proprietary or special infill types. As mentioned, Lightning infill is unique to Cura (now also adopted in PrusaSlicer 2.6+ as a Lightning setting) and is geared for ultra-fast, low-density fills for supports and top layers. It’s not intended for strength, but great for speed when printing non-functional parts. Concentric infill is another pattern (available in many slicers) that prints infill following the contour of the part’s outline; it’s often used for flexible prints or to get smooth force distribution in deformable objects.

• Naming Differences: In PrusaSlicer (and SuperSlicer), Grid refers to a pattern where lines cross every layer (what we called grid here), while Rectilinear is the one-direction-per-layer pattern. In Cura, Lines is one-direction and Grid is two-direction per layer – so just be mindful that the same term can mean slightly different patterns depending on the slicer. Similarly, Cubic infill is available in both Cura and PrusaSlicer and generally means the 3D cube lattice pattern we described. Gyroid is now common to many slicers and is usually called “Gyroid” universally, given its mathematical name.

When switching slicers or following print advice, double-check these terminology differences to select the right infill type. Most slicers’ documentation or tooltips clarify what each pattern is. In any case, the fundamental considerations remain consistent: choose the infill pattern and density that best suit your part’s use-case, whether that’s maximizing strength in critical areas or minimizing material for a quick draft print.