What happens if the extrusion multiplier is set incorrectly?

When the extrusion multiplier is set incorrectly, it primarily affects the volume of filament that is extruded through the nozzle. An incorrect setting can lead to over-extrusion or under-extrusion, which directly impacts the print quality. Over-extrusion occurs when too much filament is extruded, resulting in blobs, stringing, or a messy appearance to the print. Conversely, under-extrusion happens when there isn't enough filament being laid down, leading to gaps in the layers, weak structures, or even print failures where parts do not adhere properly.

Therefore, adjusting the extrusion multiplier is crucial for achieving accurate layer thickness and overall print fidelity. Proper calibration ensures that the correct amount of material is used, which is vital for successful prints. The other options do not adequately address the specific consequences of an incorrect extrusion multiplier setting on the print results and quality, making the focus on over-extrusion and under-extrusion the most relevant outcome.