Additive manufacturing, particularly fused filament fabrication (FFF), has developed from a prototyping technique into a versatile technology that supports design, production, and maintenance across multiple industries. This chapter reviews the fundamental principles of FFF, including extrusion-based deposition of thermoplastic filaments, the influence of process parameters, and the role of material selection in determining part quality. The advantages of FFF include low equipment and material costs, ease of operation, and wide availability of compatible polymers and composites. Limitations such as anisotropic mechanical properties, restricted dimensional accuracy, and layered surface finish are also discussed. Applications are presented in aerospace, automotive, biomedical, construction, consumer products, education, and creative industries. In aerospace, FFF enables rapid prototyping of aerodynamic models, lightweight noncritical components, and specialized tooling. In the automotive sector, it supports design verification, custom jigs and fixtures, and functional parts in low-volume or specialized vehicles. Emerging developments such as multimaterial printing, composite filaments, process monitoring, and AI-assisted optimization are expanding the scope of FFF. Sustainability and recycling of thermoplastics remain important challenges. The chapter emphasizes the integration of FFF into broader digital manufacturing strategies and highlights its role in distributed and on-demand production. FFF is positioned as an accessible and adaptable technology that connects digital design with physical realization and offers significant potential for decentralized and customized manufacturing in the future.
