Beginner Guide

What Is Infill in 3D Printing?

Infill controls the inside of your print: strength, weight, material use, and how long the job takes.

Cutaway 3D printed part showing internal infill patterns for strength weight and print time

Quick Answer

Infill is the internal structure printed inside a 3D model. A 0% infill part is mostly hollow, while 100% infill is solid plastic. Most beginner FDM prints work well at 10–20% infill, while functional parts often need stronger walls, better orientation, and sometimes 25–40% infill.

Infill is one of the easiest slicer settings to change, but it is also one of the most misunderstood. More infill can help, but it is not a magic strength button.

What Infill Percentage Means

Infill percentage tells the slicer how much internal structure to print. A 15% infill part has sparse internal supports. A 50% infill part has a much denser interior, uses more filament, and takes longer to print.

Best Infill Settings for Beginners

Decorative prints: 5–10%
General prints: 10–20%
Functional parts: 20–40%
Flexible TPU: adjust based on squish and part feel
Maximum strength: improve design, orientation, and walls before jumping to 100%

Best Infill Patterns

Grid is simple and common. Gyroid is strong in multiple directions and often prints smoothly. Lines are fast. Cubic can be useful for stronger functional parts.

Walls Often Matter More Than Infill

For many FDM parts, adding another wall/perimeter improves strength more efficiently than raising infill. If a bracket breaks at the edge or layer lines, more infill may not solve the real problem.

Rule of thumb: Try 3–4 walls and 15–25% gyroid infill for practical everyday parts.

Related PrintPilotLab Guides

For stronger parts, read how to design strong FDM parts and review slicer settings that actually matter.

FAQ

Is 20% infill strong enough?

For many everyday prints, yes. Functional parts may need more walls, better material, and improved print orientation.

Is 100% infill worth it?

Rarely for beginners. It uses much more filament and can create stress, warping, and long print times.

What infill is best for PLA?

For general PLA prints, 10–20% grid or gyroid is a good starting point.

Print better with fewer surprises

Use this guide with PrintPilotLab’s beginner setup, slicer settings, and troubleshooting resources to make smarter printing decisions.

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