Z-offset: fine-tuning the first layer

What Z-offset sets

After bed leveling the printer knows where the surface of the bed is, but the exact nozzle distance still has to be fine-tuned. A shift on the Z (vertical) axis of 0.02 to 0.05 mm is already visible on the first layer.

A correct Z-offset means the plastic is gently pressed onto the plate and the neighbouring lines merge into a smooth surface. The value is therefore found between two extremes: the nozzle must not be too high, and it must not squash the plastic out sideways either.

Signs of a wrong Z-offset

• Too high. The first-layer lines are round and not joined, with gaps between them. The part holds badly and may come loose (adhesion).
• Too low. Plastic is squeezed out sideways, the underside is glossy and wavy and the edges are puffed up, giving elephant foot. In an extreme case the nozzle scrapes the plate.
• Just right. The underside is flat, the lines blend together, the colour is even and the part can be released without effort.

What you see of it on the finished part

Z-offset is set for the build plate and the material, not for an individual order. You do not set anything, but the quality of your part's underside comes directly from a correct Z-offset. If the underside looks rough to you or has sloping edges, rotate the model or write to us.

When designing, bear in mind that the bottom 0.2 to 0.4 mm or so may be a little wider than the rest (tolerances). If a part has to fit exactly into an opening, give the bottom edge a bevel (chamfer).

Z-offset and different materials

Each material behaves a little differently. Softer PETG spreads more under pressure than PLA, and so needs a slightly larger distance. It also varies with different plate surfaces. For that reason Z-offset is set for the combination of material and plate.

The values do not change with every print, but they are checked when a plate is replaced, after maintenance and when an obvious first-layer fault appears.