Which print quality issue is directly related to improper cooling in FDM printing?

In Fused Deposition Modelling (FDM) printing, warpage is directly related to improper cooling. This issue occurs when printed layers do not cool evenly or at the correct rate, which can lead to distortion or contraction of the material as it solidifies. Warpage typically manifests as curling or lifting of the edges of a part, particularly in larger prints or those with significant height. It arises when the outside layers cool faster than the inner layers, creating stress within the material. This differential cooling can cause parts to lift off the build plate or warp in shape, negatively affecting print quality and accuracy.

The other options may result from different factors: stringing is often due to excessive nozzle temperature or retraction settings; weak layer adhesion can arise from insufficient extrusion or inadequate bonding between layers; and surface roughness usually relates to nozzle wear, print speed, or the print head's flow rate. Each of these issues is distinct and not primarily caused by improper cooling as warpage is.