A wide range of thermoplastic polymers can be processed with FDM technology, the most common of which are PLA, ABS, NYLON or PET. Materials such as TPU have elastomeric characteristics allowing flexible parts to be printed. On the highest performing machines it is also possible to print engineering grade polymers such as PEEK and PEI. Water-soluble support materials such as PVA can be used. There are some filaments in composite material, consisting of a polymer matrix and charged with fibers (Example: Nylon charged with carbon fiber or glass fiber). There are metal-filled filaments, which are molded as normal materials, requiring a post-sintering process in which the thermoplastic matrix evaporates leaving completely metallic parts.
The materials are commonly marketed in the form of spools of filaments (standard diameter 1.75mm or 2.85mm). Some machines, especially large-format ones, use polymers in the form of pellets, which are much cheaper and in some cases derive from recycled plastic.