What is a common limitation associated with FDM's surface finish?

In Fused Deposition Modelling (FDM), surface finish is significantly influenced by layer thickness. When using thicker layers, the printing process is faster, which can lead to a lower overall surface quality. This is primarily because thicker layers result in more pronounced visible layer lines and irregularities, making the surface rougher.

Choosing thinner layers can improve the surface finish, as they allow for a more refined detail and smoother transitions between each layer. However, while thinner layers improve quality, they also require more time to print. Thus, there is a trade-off between print speed and surface quality that is characteristic of FDM. This understanding emphasizes why thicker layer heights typically degrade surface finish, supporting the correct answer regarding the common limitations of FDM in achieving smooth surfaces.