Walls (perimeters): the outline of a 3D print

How they are made

The printer first goes around the outline of a layer, and that is the first wall. Further walls are added inwards. The interior is then filled with infill. The result is like a shell with a sparse foam inside. According to OrcaSlicer, more walls improve how the layers hold together, the strength and the appearance, but they lengthen the print and use more material.

One wall is about as wide as the nozzle, so with our 0.4 mm nozzle around 0.4 to 0.5 mm. Three walls give a shell about 1.2 to 1.5 mm thick.

Why walls decide strength

When a part bends or takes a knock, the surface is stressed most, not the middle. That is why strength depends more on the walls than on the infill density. A part with 4 walls and a sparse infill is often stronger than one with 2 walls and a dense infill. With thin parts the walls moreover fill the whole cross-section and there is no infill at all.

What to watch out for in the design

• A thin wall in the model should be a multiple of the line width, that is roughly 0.8 mm, 1.2 mm, 1.6 mm. In between, the slicer has to fill gaps or leaves them out.
• Walls thinner than about 0.8 mm can come out weak or not print at all, see also the entries on wall thickness.
• You do not have to draw the walls separately. The number of walls is a setting at print preparation, not part of the file, and the model only has to have walls that are thick enough.

How it works with us

You choose strength with three levels of infill (10%, 15%, 40%) and we add supports automatically. You do not set the number of walls in the calculator. If you need a part resistant to bending, choose the strong infill and design thicker walls right in the model, ideally with sufficient wall thickness.

Walls and the width of a printed line

A 0.4 mm nozzle does not print a line exactly 0.4 mm wide, but usually 0.42 to 0.5 mm. In practice walls are therefore as thick as a multiple of that value. If you design a 1 mm wall, the slicer adjusts it by combining two lines, and the gap may be filled or the wall may come out thinner. The safest is to design walls at 0.8, 1.2 or 1.6 mm.

Watch out for watertight boxes and containers. To avoid leaking they need at least two walls and a properly bonded first layer. We cannot guarantee watertightness, though, as it depends on the shape of the model.