3D Printing Wall Thickness Guide

Wall thickness is one of the first numbers you choose on a printed part and one of the easiest to get wrong. A wall that's too thin prints with gaps, flexes, or snaps the first time someone uses the part. A wall that's thicker than it needs to be costs print time and material and can warp. The right number depends on your printer, your material and what the wall has to do.

This guide gives starting points for the common processes, explains why the answer on an FDM printer is really about whole extrusion widths, and ends with a small test print that finds the number for your own machine.

The ranges below are general starting points from common design guidance, not specifications. Printers, materials, resins and slicer settings all change the result, so confirm them with a test print, check your service provider's design guide if you're ordering parts, and have anything safety-critical or load-bearing reviewed by an engineer who knows the application.

Starting points by process

FDM with a 0.4 mm nozzle: about 1.2 mm (three perimeters) is a solid default for functional parts. Around 0.8 mm (two perimeters) works for light-duty and cosmetic walls. A single 0.4 mm perimeter prints, but it's fragile and best kept to decoration.
FDM, load-bearing or screwed-into walls: go to 2 mm or more, which is four or five perimeters on a 0.4 mm nozzle, and add ribs or fillets where the load enters.
Resin (SLA and similar): published minimums run roughly from 0.5 to 1 mm depending on the resin and whether the wall is supported at both ends. Tall, unsupported thin walls can warp or break when they're peeled off the build plate or cleaned.
Powder nylon (SLS or MJF): service bureaus commonly list minimums somewhere around 0.7 to 1 mm, with a bit more for walls that need to be stiff. Their design guide for the exact process and material you're ordering is the number to trust.

On FDM printers, think in whole line widths

A slicer builds a wall out of perimeters, which are lines of plastic roughly as wide as the nozzle. With a 0.4 mm nozzle those lines are often about 0.4 to 0.45 mm wide (check your slicer's setting). A wall that's a whole number of those widths prints as clean, solid perimeters. A wall that isn't leaves a sliver that the slicer either fills with a thin gap-fill line or leaves out.

That's why 1.2 mm is a better choice than 1.0 mm on a 0.4 mm nozzle: 1.2 mm is three perimeters exactly, where 1.0 mm is two perimeters and a leftover. Look at your slicer's preview before you print. If a wall you modeled shows fewer perimeters than you expected, or doesn't show up at all, change the thickness or the line width.

Strength comes from the perimeters

On an FDM print, the outer perimeters carry most of the load, and the infill mostly keeps them apart. For a part that has to be stiffer or stronger, adding a perimeter or two usually does more than raising the infill percentage, and it costs less print time. Infill matters more for flat tops and for keeping the walls from buckling inward under pressure.

Strength also depends on direction. Layers are the weak plane of an FDM part, so a wall that's pulled across its layers fails far more easily than one that's pulled along them. If a thin wall has to carry a load, orient the part so the load runs along the layers.

Height changes the answer

Tall thin walls wobble. A wall that's fine at 10 mm tall can chatter during printing and flex in use at 60 mm. Thicken it, or tie it to the neighbouring wall with ribs.
Add ribs instead of thickness. A thin wall with ribs is stiffer than a slightly thicker plain one and uses less material. The DFM checklist for small enclosures has guidance on rib size.
Thicken at the base. A fillet where a wall meets the floor spreads the stress that would otherwise concentrate there.
Large flat walls warp. A broad thin panel curls as it cools. Curved edges, ribs or a slightly thicker wall help.

Walls around holes, threads and screws

Keep at least two perimeters around a hole. The wall beside a hole is where cracks start, and a hole close to an edge leaves too little plastic to hold a screw.
Screws and threaded inserts need material. Size the wall around a screw hole or an insert from the maker's chart rather than eyeballing it, and use more perimeters in that area.
Watch for liquid and pressure. Thin printed walls can leak through the gaps between layers. Anything that holds fluid or pressure needs solid walls, and often a coating or a different process. The adapter guide covers sealing printed parts.
Small details need depth. Embossed text and fine features that are thinner than a line width simply don't print on FDM; make them at least one line wide and a couple of layers tall.

Print a wall-thickness test

The quickest way to find your own numbers is a small stepped test piece, the same idea as the tolerance coupons in our 3D-printed adapter guide. Model a row of thin vertical walls about 15 to 20 mm tall, stepping from 0.4 mm up to 2.0 mm in 0.2 mm increments, joined to a common base. Print it in the material, orientation and settings you'll use for the real part. For clearances between parts, see 3D printing tolerances.

Look at the slicer preview first and note which walls show full perimeters and which show gaps.
After printing, check each wall for gaps and holes. Hold the test piece up to a light: thin spots show through.
Flex each wall with a fingernail or a pair of tweezers and note where it goes from fragile to solid.
Pick a wall thickness from the first step that feels solid, then round up to a whole number of line widths. Add a perimeter on any wall that carries load.

A quick checklist

Choose a thickness that's a whole number of line widths for your nozzle.
Use two perimeters as the floor for cosmetic walls and three or more for functional ones.
Add ribs and fillets before adding thickness on tall or broad walls.
Keep extra material around holes, screws and inserts.
Print a wall test in your real material before you commit to a long print, or an order.

If you're designing something that has to be printed in volume, or the walls have to meet a load or sealing requirement, the numbers above are a starting point. We design parts and enclosures for printing and for molding, and we'll tell you what your design needs. Tell us what you're building.