Print settings
Infill
How solid the inside of your part is. The outer walls stay the same either way, infill is the internal lattice hidden underneath. Lower saves money; higher adds strength and weight.
What infill is
Picture a solid cube in CAD. If we printed it 100% solid, every internal millimetre would be plastic, heavy, slow and expensive. Instead, FDM printers build a solid shell of outer walls, top and bottom layers, then fill the hollow interior with a lightweight lattice. That lattice is the infill. It's what holds the top surface up and gives the part its internal stiffness.
Infill is set as a percentage: 0% is fully hollow (with just the top and bottom layers spanning across), 100% is fully solid. Everything in between is a lattice of varying density.
How to choose a density
We accept any value from 10% to 100% in 5% steps. Below 10% the top layer often sags between the lattice cells; above about 60% you rarely gain useful strength, because the outer walls carry most of the load anyway.
| Density | Feels like | Weight | Cost | Use for |
|---|---|---|---|---|
| 10% | Very light, hollow-ish | Lightest | Cheapest | Display models, cosplay, non-load-bearing shapes |
| 15% | Light | Very light | Very cheap | Prototypes you don't intend to load |
| 20% | Solid enough (default) | Light | Baseline | Almost every part, the pre-selected default |
| 30% | Noticeably stiffer | Moderate | Slight bump | Brackets, jigs, mildly loaded parts |
| 50% | Stiff, dense | Heavy | +15–25% | Structural parts, threaded inserts, tools |
| 80% | Nearly solid | Very heavy | +30–45% | Fatigue-critical parts, or anything you plan to tap threads into |
| 100% | Fully solid | Solid plastic | +50–70% | Only when you need it, usually cheaper to redesign with ribs |
Cost figures are relative to a 20% baseline for a typical part. Small, wall-dominated parts see less difference.
Start at 20%, adjust if you have a reason
20% is the pre-selected default in our quote engine because it's genuinely the right answer for most parts. Bump it up when the part is loaded, fatigued, or needs to accept a threaded insert. Bump it down when the part is purely visual.
Infill vs walls, where the strength really comes from
A common mistake is cranking infill to 100% to make a part stronger. It's usually the wrong lever. The outer walls, the perimeters that trace your CAD surface, carry the vast majority of the load in a printed part. Going from 20% to 50% infill on a typical bracket adds maybe 10–15% real-world strength, but adds 25% to the print time.
You can't currently choose the wall count directly in the quote engine, it's set automatically based on the part and material. If a part specifically needs thicker walls, mention it in the checkout notes or contact us first and we'll set it manually.
For a stronger part, in order of value for money: add ribs in CAD, orient the part so layer lines don't cross the load path (see orientation & strength), then increase infill, then increase wall count.
Infill patterns
We use two patterns as standard, picked automatically per part based on the material, size and how the part is likely to be loaded:
- Rectilinear, straight parallel lines, alternating direction every layer. Fast to print, reliable on flat, chunky parts, and great when you need predictable behaviour under a single-direction load.
- Gyroid, a continuous, wavy 3D lattice. Roughly the same strength in all directions (isotropic), which makes it the right choice for functional parts, TPU, and anything that gets pushed and pulled from multiple angles.
You can't select the pattern in the quote engine, the shop picks whichever works best. If you specifically need a different pattern (honeycomb, cubic, concentric, or 100% single-direction), add a note at checkout or contact us directly and we'll set it manually before printing.
What it costs you
Every extra percent of infill is a little more plastic and a little more print time. The relationship isn't linear, going from 20% to 30% costs less than going from 80% to 90%, because the outer shell is already using most of the time. Our quote engine updates the price live as you drag the slider, so you can see exactly what each step costs on your part.
- 10–20%, cheapest tier, best for display and prototype work.
- 30–50%, modest uplift, big strength gain for functional parts.
- 60–100%, expensive fast. Consider a heat-set insert or a rib instead.
Common pitfalls
- Picking 100% to feel safe. Almost never worth it. If the part fails at 20%, it will usually fail at 100% too, the fix is orientation, walls, or a different material.
- Picking 10% on a threaded part. Threads and inserts need material to bite into. Use 30% minimum where a fastener enters the part.
- Picking 10% on a tall, thin part. The top layer can sag between sparse lattice cells. Either raise the infill or thicken the top layers (mention it in checkout notes).
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Last reviewed May 2026 · Rigid Prints engineering team