When you want a strong 3D print, it’s natural to think:
“Why not just set infill to 100%?”
While it sounds logical, 100% infill is rarely necessary—and often causes more problems than benefits.
In this guide, you’ll learn why 100% infill usually isn’t the best choice, the downsides you might not expect, and better alternatives for achieving strength, weight savings, and efficient printing.
What Is Infill in 3D Printing?
Infill refers to the internal structure printed inside the outer walls (shell) of a 3D print.
It provides internal support for walls, tops, and functional strength without using as much material as a fully solid part.
| Typical Infill Range | Usage |
|---|---|
| 10–20% | Cosmetic parts, light models |
| 30–50% | Functional prototypes, moderate strength |
| 60–80% | High-stress parts, mechanical components |
| 100% | Only for very specific engineering cases |
Why You Should Avoid 100% Infill (for Most Prints)
1. 100% Infill Wastes Filament and Time
- Print time skyrockets — solid prints can take 2–3× longer.
- Massive material usage — you’ll burn through spools unnecessarily.
- Energy consumption increases, raising costs for long prints.
📌 Unless absolutely needed, the extra cost and time aren’t justified.
2. Risk of Warping and Cracking
- Fully solid parts shrink more during cooling, leading to warping or internal cracks.
- Larger solid objects trap heat, then shrink unevenly as they cool.
Materials like ABS, ASA, and Nylon are particularly vulnerable to splitting when printed at 100% infill.
3. Prints May Become Too Heavy
- A 100% infill part can be significantly heavier than necessary.
- If you’re building parts for drones, robots, wearables, or portable tools, excess weight is a major problem.
4. Minimal Strength Gains Beyond 60–80%
Most 3D prints achieve 95–98% of their maximum strength around 60–80% infill.
Adding 20–40% more material rarely makes parts much stronger—it just makes them heavier and harder to print.
📌 Studies have shown that strength improvements flatten out sharply beyond 60–80% infill.
When 100% Infill Does Make Sense
- Small parts (less than 2×2×2 cm) that need to be very tough
- Tooling fixtures that require extreme stiffness
- Molds for silicone casting where smooth, non-porous interiors matter
- Threads and taps (printed directly into a part)
Even then, it’s usually smarter to reinforce only critical zones, not the entire model.
What to Do Instead of Using 100% Infill
1. Increase Wall (Perimeter) Count
Walls contribute far more strength than infill does.
| Part of Print | Contribution to Strength |
|---|---|
| Outer Walls | 60–80% |
| Infill | 20–40% |
Recommended Wall Settings:
- 3–5 walls for strong parts
- 5+ walls for mechanical, load-bearing parts
📌 Adding walls boosts impact resistance and flexural strength much more efficiently than infill.
2. Use Strong Infill Patterns
Some infill geometries provide strength without needing high density:
| Infill Pattern | Strength | Notes |
|---|---|---|
| Gyroid | High | 3D strength in all directions, fast to print |
| Cubic | High | Good for large, structural parts |
| Triangular | High | Great for flat load-bearing prints |
Choose a strong 3D pattern rather than bumping infill to 100%.
3. Use Higher Infill Percentage Strategically
- Use 40–60% infill for most mechanical parts.
- Go to 70–80% if you need near-solid parts.
- Combine with adaptive infill (higher density near critical areas) if your slicer supports it.
Tip:
Some slicers like PrusaSlicer, SuperSlicer, or Cura allow variable infill density—denser inside shells, lighter toward the center.
4. Choose Stronger Materials
Instead of overcompensating with 100% infill:
- Switch to PETG, ABS, Nylon, or Carbon Fiber Reinforced filaments.
- These materials offer inherently higher strength even at lower infill percentages.
5. Optimize Part Orientation
Print orientation has a huge impact on strength.
- Layers are weakest between themselves (Z-axis).
- Design parts so that load runs along the layer lines where possible.
Sometimes better design beats overbuilding with infill.
Real-World Example: Strength Without 100% Infill
| Setup | Infill | Walls | Result |
|---|---|---|---|
| Test #1 | 100% infill | 2 walls | Cracked near center under load |
| Test #2 | 60% gyroid infill | 5 walls | Survived greater load without cracking |
📌 Strong outer walls + smart infill pattern > 100% solid block every time.
FAQs
Q1: Does 100% infill make parts completely solid?
Not always. Even 100% infill still leaves micro gaps between extrusion lines unless printed perfectly.
Q2: Should I ever use 100% infill for hobby prints?
Rarely. 40–60% infill with 3–4 walls is more than enough for most models, miniatures, and props.
Q3: Will 100% infill improve part waterproofness?
Yes, it can, but so can extra walls and proper wall overlap settings. You don’t need full infill to achieve waterproof parts.
Q4: How much heavier is a 100% infill print?
Up to 2–3× heavier than a 20–30% infill print of the same size.
Conclusion
While it’s tempting to crank infill to 100% for strength, it’s usually unnecessary, wasteful, and even risky for your prints.
Instead, focus on higher wall counts, smart infill patterns, strong materials, and optimized design.
By balancing infill and walls intelligently, you’ll achieve stronger, lighter, and faster prints—without wasting filament, time, or risking warping.