Infill Guide

Infill in 3D Printing

Definition of Infill

  • Infill: The internal structure inside a 3D printed part that influences various attributes of the final product, such as:

    • Strength: Affects how much load the part can withstand.

    • Weight: Heavier infill contributes to increased weight of the part.

    • Print Time: More infill requires more time to print.

    • Durability: Affects the overall robustness of the part.

Choosing Infill in Slicer Software

  • Infill settings are typically selected in slicer applications (e.g., Cura, PrusaSlicer).

Description of Infill

  • What Is Infill?: It is the pattern that is printed inside a part between the outer walls. The percentage of infill can drastically change the characteristics of the printed part:

    • 0% Infill: Hollow part.

    • 100% Infill: Solid part.

    • 15–40% Infill: Commonly used for FTC (FIRST Tech Challenge) parts.

Impact of Infill Density

  • More Infill: Results in stronger parts but also increases weight and print time.

Common Infill Patterns

1. Grid Pattern

  • Description: A square grid pattern stacked layer by layer.

  • Attributes:

    • Simplicity: Easy to implement.

    • Strength: Offers decent strength.

    • Print Speed: Fast printing.

    • General Use: Good for a variety of non-critical parts.

  • Weakness: Not optimal under multi-directional stress.

  • Use Cases:

    • Basic brackets

    • Light-load parts

2. Lines Pattern

  • Description: Composed of straight parallel lines with alternating directions for each layer.

  • Attributes:

    • Speed: Very quick to print.

    • Strength: Low overall strength.

    • Weight: Lightweight construction.

  • Use Cases:

    • Cosmetic parts

    • Covers

    • Low-stress components

3. Triangles Pattern

  • Description: Features interlocking triangles.

  • Attributes:

    • Strength: Stronger than grid patterns due to effective load distribution.

    • Speed: Maintains reasonable print speed.

  • Use Cases:

    • Moderate load brackets

    • Structural components

  • Note: Triangles resist deformation effectively.

4. Honeycomb Pattern

  • Description: Comprises hexagonal cells.

  • Attributes:

    • Strength-to-Weight Ratio: Extremely favorable.

    • Impact Resistance: Good under shock loads.

    • Print Speed: Slower to print compared to other patterns.

  • Use Cases:

    • High-stress parts

    • FTC mounts that operate under load

5. Gyroid Pattern (Very Popular)

  • Description: Curved, wave-like 3D structure.

  • Attributes:

    • Strength: Excellent in multi-directional strength.

    • Stress Distribution: Smooth distribution of stress throughout

    • Design: No sharp corners inside, aiding in durability.

    • Efficiency: Strong yet material-efficient.

  • Use Cases:

    • Load-bearing brackets

    • Arm components

    • Motor mounts

  • Recommendation: Gyroid is usually the strongest choice for FTC applications.

6. Cubic Pattern

  • Description: Consists of a 3D cube lattice structure.

  • Attributes:

    • Strength: Strong in multiple directions, providing robustness.

    • Material Usage: Higher than grid pattern.

  • Use Cases:

    • Strong structural parts.

7. Concentric Pattern

  • Description: Constructed with rings that align with the outer walls.

  • Attributes:

    • Strength: Not structurally strong but offers flexibility.

  • Use Cases:

    • Cosmetic or cylindrical parts.

Infill Percentage

  • Pattern types are important, but the percentage of infill is even more critical.

  • Typical FTC Infill Settings:

    • 15–20%: Suitable for lightweight brackets.

    • 30–40%: Appropriate for structural components.

    • 50% or more: Used for high-load applications but often wasteful at 100%.

  • Alternative Adjustments:

    • Instead of excessively increasing infill, consider increasing:

    • Wall thickness

    • Top and bottom layer counts

    • Note: Walls contribute significantly more strength than infill itself.

Factors Affecting Strength of 3D Printed Parts

  • Answering What Makes a 3D Printed Part Strong:

    • Infill pattern

    • Infill percentage

    • Wall thickness

    • Layer adhesion

    • Print orientation

  • Importance of Print Orientation: It plays a crucial role in strength, as parts are typically weakest between layers.

FTC-Specific Advice for Robotics

  • Recommended Defaults:

    • Infill Pattern: Gyroid

    • Infill Percentage: 25–35%

    • Wall Count: 3–4 walls

    • Print Orientation: Proper alignment is essential.

  • Avoidances:

    • Long unsupported thin prints.

    • Over-reliance on 3D printed parts for applications demanding high torque.

  • Comparison: While printed parts have their strengths, they are generally inferior to aluminum in terms of structural integrity.