Infil

Infill refers to the internal lattice structure within 3D-printed parts, balancing strength, material efficiency, and print time. Unlike solid parts, infill reduces weight and filament usage while maintaining structural integrity. Key considerations include geometry, mechanical requirements, and material properties.

Infill Density and Application

Density Guidelines

• Decorative/Prototype Parts: 8–15% – Minimizes material use while maintaining basic shape.

• Functional/Mechanical Parts: 20–40% – Provides structural support for moving components or load-bearing surfaces.

• High-Strength Parts: ~50% – Suitable for tools, connectors, or parts subjected to repeated stress.

• Special Cases:

  • 0%: Viable for thin-walled objects (e.g., enclosures) if shells provide sufficient rigidity.

  • 99%: Reserved for niche applications like firearm frames, prioritizing density over efficiency.

Diminishing Returns: Infill above 50% rarely improves strength significantly but increases print time and material usage.

Geometry Considerations

• Thin-Walled Parts: Infill has minimal impact; prioritize shell thickness (e.g., 3–4 walls).

• Large/Thick Models: Higher infill (20–50%) prevents sagging and ensures layer adhesion.

Infill Patterns and Performance

Common Patterns

• Grid: Fast printing with moderate strength; prone to nozzle clogging on overlapping lines.

• Triangles: Balances speed and directional strength; ideal for general-purpose prints.

• Gyroid: Isotropic strength and vibration resistance; slower to print but avoids directional weaknesses.

• Cubic Subdivision: 3D grid structure for uniform load distribution; suitable for complex stress points.

• Lightning: Ultra-low density (5–10%) with strategic supports; prioritizes speed over durability.

Pattern Selection:

• Speed: Grid, Triangles, Lightning.

• Strength: Gyroid, Cubic, Octet.

• Aesthetics: Concentric (visible in translucent prints).

Advanced Infill Parameters

Infill Overlap

• Range: 8–12% overlap with shell walls ensures bonding without visible lines.

• Trade-offs: Higher overlap (>15%) risks surface artifacts; lower values (<5%) weaken shell-infill adhesion.

Layer Thickness

• Default: Matches overall layer height (e.g., 0.2mm).

• Optimization: Increase infill layer thickness (e.g., 0.3mm) for large models to reduce print time.

Print Order

• Infill Before Walls: Reduces "veiny" surface textures but may compromise dimensional accuracy.

• Infill After Walls: Default setting prioritizes surface quality.

Troubleshooting Infill Issues

• Pitted Top Surfaces: Increase infill density (≥20%) or add top layers (4–6 layers).

Print with too little top layers or too low of infill causing a "pitted" look

• Visible Infill: Reduce overlap, increase shell walls (≥3), or use translucent-friendly patterns (e.g., Gyroid).

• Weak Layer Bonding: Adjust infill pattern (e.g., Gyroid for isotropic strength) or raise nozzle temperature.

Practical Workflow for Infill Optimization

1. Assess Part Requirements:

   • Determine load direction (e.g., vertical vs. lateral).

   • Identify critical surfaces (top/bottom vs. sides).

2. Calibrate Settings:

   • Start with 15% infill for prototypes; adjust based on stress tests.

   • Use temperature towers and infill density tests for material-specific tuning.

3. Post-Processing:

   • Sand or coat translucent parts to mask infill visibility.

   • Reinforce high-stress areas with localized infill density (slicer-dependent).