The layer height of a 3D print is also known as the resolution, the smaller the layer height, the finer the resolution and less noticeble the layers become.

Despite the nozzle on your 3D printer having a fixed diameter, it is possible to change the layer height by configuring the amount of plastic the extruder pushes through the hot end.

In Slic3r, select “Print Settings”, “Layers and perimeters” and tweak the layer height. Easy Peasy. Well almost.

A screenshot of the slic3r application

If you try going too large, you will run into an error “–layer-height can’t be greater than –nozzle-diameter”. Well that kind of makes sense, you can’t make a layer taller than the nozzle is wide. In order to build thicker layers, you need a larger nozzle diameter.

There is also a lower bound, as the layer height gets smaller and smaller it becomes increasingly difficult for your 3D printer to accurately push smaller and smaller amounts of plastic out the nozzle.

So what is the sweet spot, where the layer height is just right? Well it is a combination of both layer height and extrusion width. The extruded plastic needs to form a nice oval shape (see diagram below), rather than a circular shape. This creates a nice surface area for layers in the print to bond together. So a layer height less than the nozzle diameter is ideal, but how much less?

A sketch showing the ideal amount of squish between 3D printed layers

Slic3r defaults to a layer height that is 80% of the nozzle diameter, which is right in line with the awesome calibration guide by Triffid Hunter. There is also the kick-arse calculator by Josef Prusa, where you can punch in the nozzle diameter of your printer and it will make a recommendation on layer height (about 60% of the nozzle diameter).

And if you are ready to get really experimental with slic3r, you can start to play around with the extrusion width which you will find under “Advanced” in print settings.


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