First-Layer Calibration

Theory

The first layer must be slightly compressed against the bed to achieve mechanical adhesion. The Z offset defines the nozzle height above bed zero. Too far: the layer is a round bead with poor adhesion. Too close: the nozzle scrapes the bed. The ideal gap is 50-80% of layer height, creating a slight squish visible as a flattened elliptical bead. Bed tramming ensures this gap is uniform across the full area.

Application

Use paper-thickness test (0.1 mm) for initial Z offset. Fine-tune with baby stepping during the first layer in real time. Print a large flat square to verify uniformity and adjust levelling screws or use mesh bed compensation. Always check Z offset after a nozzle change or crash.

Common mistakes

A Z offset 0.05 mm too high causes first-layer failure on small-footprint parts; 0.05 mm too low grinds nozzle on glass. Bed temperature changes the physical gap through thermal expansion: always set Z offset at target print temperature. ABL probe offsets must be recalibrated when changing nozzle diameter.

Related terms: Bed Adhesion, Warping, Elephant Foot