The first printers that spread on the market used filament technology: through the extrusion of a thread of material (PLA, ABS, etc.) different levels were built up to the completion of the detail. This technology, suitable only for the realization of prototypes, because of the length of the manufacturing process, allows only the creation of fragile pieces, with low mechanical properties and with a mediocre surface finish.
Subsequently, different types of printers arrived on the market (laser sintering, polyjet, etc.), always usable only for the realization of prototypes and non-functional parts.