How Much Infill Do You Actually Need?

Infill is the setting customers ask us to raise most often, and it's usually the wrong lever. Understanding it will save you money on almost every order.

Answer three questions first

1. Does the part carry weight, or just sit there?
2. Does it need to survive being dropped or knocked?
3. Does weight matter? Drones, RC parts and anything handheld are sensitive to this.

These land you in a band, not on a number.

What infill actually is

Printed parts aren't solid. Inside the outer shell is a lattice, a honeycomb or wave pattern that supports the top surface and adds stiffness. Infill density is how tightly packed that lattice is. At 20%, roughly a fifth of the interior is plastic and the rest is air.

That air is doing more work than it looks like it is.

The three bands

10-15%: display and fit-check. Models, prototypes, decorative pieces, anything checking that a shape is right.

20-25%: general purpose. The default for most parts. Organizers, enclosures, mounts, brackets under light load. Unless something specific pushes us off it, this is where we start.

40-50%: load-bearing. Parts taking real force, absorbing impact, or holding a threaded insert. Above this, returns fall off sharply.

Why more isn't better

Going from 20% to 50% roughly doubles material and machine time, so it roughly doubles what you pay, while adding maybe a third more strength. Two extra wall passes cost a fraction of that and often do more, because the shell carries most of the load.

That's the trade nobody sees on a quote. Infill is the expensive way to buy strength. Walls are the cheap way.

Solid is almost never the answer

100% infill is slower, heavier, more expensive and more likely to warp than a well-designed part at 40%. The pressure that builds inside a fully packed part works against you. We'll do it if you need the mass, but we'll ask why first.

When high infill is a symptom

If a part seems to need more than 50% to survive, the problem is usually somewhere else. Wrong material. A sharp internal corner starting a crack. Load running across the layers instead of along them. Cranking infill treats the symptom and bills you for it. Five minutes on the geometry is cheaper.

What to tell us

You don't need to pick a number. Tell us what the part does and how it's held. If we can hit the same strength for less by adjusting the walls instead, that's what you'll be quoted.