When 3D printing objects, one of the most important settings to configure is the infill pattern. Infill refers to the structure inside the walls of a 3D printed object. It serves to provide internal support and affects the strength, weight, print time, and material usage of the finished part.
Choosing the optimal infill pattern for an application is crucial to get the right balance of properties. The strongest infill patterns result in 3D prints that can withstand high amounts of force without breaking or deforming. This makes them ideal for functional parts that need to handle stress, as well as decorative items that require sturdiness.
In this comprehensive guide, we’ll compare the most common infill patterns and analyze testing data to determine which options provide maximum layer adhesion and withstand force the best.
How Infill Pattern Affects 3D Print Strength
Infill creates a framework inside the outer shell of a 3D print. It functions as an internal support structure, preventing the walls from drooping or collapsing under pressure.
The pattern of the infill significantly influences strength. Some patterns align the filament in straight vertical and horizontal lines, providing even distribution of weight. Others utilize diagonal cross-hatching for extra reinforcement across multiple axes.
Infill that interlocks and bonds between layers creates a cohesive internal structure. Patterns with gaps or spacing between filament lines produce weaker infill. The shape and layout of the pattern impacts:
- Interlocking between layers – Infill that connects between layers resists pull and shear stress better.
- Filament alignment – Straight vertical patterns withstand force pushing down best. Horizontal patterns are stronger against lateral stress. Diagonals resist torsion well.
- Gaps in infill – Spacing between infill lines produces weak points in the print. Solid patterns are stronger.
- Adhesion between walls – Infill that bonds firmly to the outer shell transfers force efficiently.
Testing infill patterns under controlled loads reveals how well they perform for different types of stresses.
3D Print Strongest Infill Patterns
These are the top infill patterns for maximizing 3D printed part strength:
1. Gyroid
Gyroid infill is one of the strongest options for FDM/FFF 3D printing. It produces a wavy, sinusoidal pattern that runs diagonally across layers, interlocking smoothly between levels.
The gyroid pattern creates a cohesive, gapless internal structure with no weak points. It links strongly side-to-side, as well as between layers. This even distribution of infill provides excellent shear and torsional strength. Parts withstand loads well from all angles.
Gyroid infill requires some processing power to generate. But it 3D prints reliably on most slicers and suits all filament types. Its wavy texture also saves slightly on material use versus a straight grid.
2. Triangles
Triangle infill generates a staggered triangular pattern, interlocking tightly between layers. The triangles alternate direction, creating a strong crisscross effect.
This interlaced geometry provides great shear and tensile strength. The triangular segments bond together firmly, resisting forces from multiple angles.
Triangle infill works well for sturdy functional prints like tool handles and bearing loads. It also suits decorative prints, giving a faceted appearance.
Most slicers like Cura include triangle infill. It prints reliably with good performance on FDM/FFF machines.
3. Cubic
Cubic infill fills space with interconnecting cube structures in a checkerboard-like grid. The cubes lock firmly between layers, distributing stress evenly across all axes.
The cubes alternate direction slightly between layers. This adds extra bonding for shear strength. Cubic infill does contain some gaps between the cubes but remains one of the strongest grid options.
It excels at resisting bending forces without cracking. Cubic infill works great for prints such as fixtures, mounts, and parts that attach to other components.
Cubic infill generally prints well on FFF/FDM machines. The pattern fits nicely within the outer walls and adheres well. It may require some slower printing on tricky geometries to span gaps cleanly.
4. Octet
Octet infill forms staggered octagonal segments in a tightly meshed pattern. The octets interlock firmly in horizontal, vertical, and diagonal directions.
This geometry gives great adhesion between layers, providing all-around strength. The interlaced octagons distribute stresses evenly throughout prints, preventing cracking or tearing.
Octet infill resists shear forces well. It works nicely for decorative prints, adding visual interest to the inside of objects. Functional prints like tools and fixtures also benefit from the strong crisscross structure.
Most slicers have octet infill built-in. It generates reliably and works with all filament types. The high density grid does use slightly more material than other patterns.
5. Cross 3D
Cross 3D infill generates three overlapping perpendicular lattice grids. The result is an extremely solid, gapless structure.
The interlaced grids provide exceptional top-down and lateral strength. Cross 3D infill prints appear almost completely solid inside. This makes it one of the toughest infill patterns.
Functional parts subject to high loads benefit greatly from Cross 3D infill. It prevents compression and deformation under pressure. The high density grid also suits decorative prints needing rigid support.
Cross 3D infill requires some processing power to generate due to the triple overlapping grids. Print times also increase slightly. But the outstanding strength gains often make it the best choice for max strength prints.
Weakest 3D Print Infill Patterns
Here are some infill patterns that test poorly for strength. Their geometry tends to produce weak points and layer separation:
- Lines – Straight horizontal infill lines leave gaps between filaments. The lack of cross-linking creates weak points vulnerable to shear forces and delamination.
- Grid – Basic grids print quickly but provide only mediocre strength. The orthogonal structure doesn’t distribute diagonal forces well. Large rectangular gaps also create vulnerabilities.
- Cubic Subdivision – This cubed pattern has improved strength over basic grid. However, gaps between sections still allow delamination, limiting max strength.
- Zigzag – Zigzagging infill allows filaments to separate side-to-side. The pattern also risks delamination errors during printing across small sections.
- Concentric – Concentric infill prints fast but provides poor strength. Its concentric rings separate easily when stressed. Large voids between rings also create weakness.
While these options work well for non-stress applications, choose interlocking patterns for optimal strength. Profiles like gyroid, cubic, triangle, and cross 3D infill provide superior layer bonding and load distribution.
How to Choose the Strongest Infill Settings
Beyond just the pattern shape, other infill settings also affect strength:
Infill Percentage
A higher infill percentage naturally makes stronger prints, by reducing voids and adding more internal structure. For maximum strength, choose 100% infill to create a completely solid part.
Most functional prints only require 20-40% infill. Going above 60% often provides rapidly diminishing returns on strength versus print time and material use.
Layer Height
Using thinner layers produces stronger infill between layers. Finer 0.12mm or 0.16mm layers allow patterns to bond together better vertically. The tradeoff is increased print time.
For tall prints needing max strength, a 0.20mm layer height provides a good balance. Larger 0.28mm+ layers speed up printing but can compromise inter-layer adhesion.
Print Temperature
Getting the optimal extrusion temperature dialed in improves infill bonding. Filament cools and hardens rapidly after exiting the nozzle.
Too low temp causes weak bonds. But too high overheats filament, causing oozing issues. Print temperature towers to find the ideal middle ground for your filament.
Print Speed
Faster printing often weakens infill bonding. High speeds reduce adhesion between lines. Slowing down allows filament more time to bond as it cools and solidifies.
Try 40-60mm/s for general prints. Drop to 30-40mm/s for maximum infill strength, allowing the best inter-filament bonding during deposition.
Real-World Infill Strength Testing
Controlled lab tests help characterize the performance of different infill patterns under standardized loads. But examining real print tests also provides practical insight.
YouTuber Make Anything compared strength between several common infill patterns by 3D printing beam samples and flex testing them until failure. Here were the results:
- Gyroid – Withstood over 150 lbs of force before bending, the strongest pattern overall.
- Cubic – Reached nearly 130 lbs before breaking, demonstrating excellent rigidity.
- Triangle – Handled over 110 lbs but showed some early inner cracking around the screw holes.
- Lines – One of the weakest patterns, failing under 60 lbs of force.
- Grid – Performed better than Lines but still fractured before 100 lbs.
These tangible tests confirm gyroid and cubic as ideal choices for high-strength applications. Triangle infill printed acceptably while line patterns should be avoided.
Optimizing Infill for Different Print Directions
The orientation of a print relative to the loading forces also impacts strength. Parts should be aligned to direct stress along the strongest print directions:
- Vertical compression – Prints strongest with vertical walls and horizontal infill lines.
- Lateral force – Outer walls parallel to force optimizes strength. Cubic infill resists well.
- Bending – Diagonal infill like gyroid performs best under flexing loads.
- Torque – Angled infill lines (45° to 65°) stand up best to twisting forces.
Considering both print orientation and infill pattern ensures prints resist breakage along their weakest axes.
Balancing Strength vs Print Time, Material Use, and Weight
While ultra-strong infill patterns like 100% gyroid or Cross 3D produce rugged prints, they also require significant print time, filament use, and extra weight.
Most prints don’t need max infill strength. For decorative prints and non-critical components, faster patterns like grid, cubic, or 20% honeycomb often work sufficiently well.
60% gyroid infill makes an excellent general-use setting, providing high strength at moderate filament and time cost. Dial back to 40% gyroid for larger prints to save material.
Always design functional parts with strength far above the expected stresses. But optimize infill to balance strength, weight, cost, and print duration for your specific application.
Key Takeaways on Maximizing 3D Print Strength Through Infill
- Interlocking infill patterns like gyroid and cubic provide excellent bonding between layers for strength.
- Triangles and octet infill also perform well, distributing stresses in all directions.
- Line, grid, and concentric patterns score lower, producing voids and weak points.
- Higher infill % naturally increases strength but also uses more material and print time.
- Smaller layer heights around 0.16mm improve vertical bonding between layers.
- Slow down print speeds to 30-40mm/s for optimal infill adhesion.
- Orient prints to direct forces along strongest axes based on infill pattern and geometry.
With the right infill choices dialed in, FDM/FFF 3D printing can produce incredibly strong parts able to withstand high loads. Use these tips to turn 3D prints into durable, long-lasting products.
