Nylon (aliphatic polyamides):

It is probably the first engineering thermoplastic. It has been used as fibers for clothing and carpets and later found applications in electronic, automotive, and industrial products. Nylon has outstanding wear resistance and low frictional properties. It has very good temperature, chemical, and impact properties. However, it has a propensity to absorb moisture and thus has poorer dimensional stability than other engineering plastics.

Traditionally extruded nylon has good mechanical properties, excellent bearing and wear characteristics. Its fatigue resistance, noise damping ability, corrosion resistance, and lightweight make nylon ideal for metal replacement applications, such as bearings, gears, sheaves, and sprockets in industrial machinery. 

Within the 3D printing community its applications mirror the more traditional technical and industrial uses to make durable parts such as bearings, gears, sheaves, and sprockets, or strong and somewhat flexible parts.

3D printing with Nylon:

Like most engineering thermoplastics, nylon will contract when cooled, therefore it will develop interlayer stress at the interface between a new hot layer 3D printed on top of a cold layer or bed surface. That can result in layer adhesion problems with the printing bed or in between 3D printed layers, and/or curling (upwards bending of the part corners and sides). This curling is more pronounced as the 3D printed object size is increased. This stress release behavior can be avoided by maintaining the entire 3D printed object at a temperature close to the glass transition temperature of the material and then cool it in its entirety after the 3D printing process is completed. Glass transition temperature is where the thermoplastic softens and becomes plastic (malleable, soft).

 3FXtrud Uno printers use a heated bed which provides consistent and uniform heating across the whole bed surface. 3FXtrud Duo series of 3D printers have a heated bed and a full enclosure around the 3D printed volume which provides a consistent, stable, uniform warm air environment around the printed objects, thus improving the whole 3D printing process by minimizing further the interlayer stress problem. 

Nylon is a generic name for a family of similar thermoplastic materials with a whole range of mechanical and thermal properties. While some Nylon will extrude at as low as 210 °C, it is more common that nylon used in 3D printers, which tend to warp less and extrude nicer, will 3D print between 230 °C to 260 °C (speed dependent). It is important to note that nylon layer adhesion is very dependent on the extruder temperature. For full strength, it is better to print at the higher end of the temperature range.

A reliable 3D printing head (or extruder) needs to withstand these temperatures for an indefinitely long time. 3FXtrud printers use a whole metal hot end design which works reliably and provides consistent 3D printing of Nylon and other engineering thermoplastics. 

3D printing requirements:

A heated bed that can operate at least 120 °C is required, along with an enclosure around the printed volume to prevent warping and a hot end that can sustain 260 °C continuously. Nylon is available in 1.75 mm and 3 mm.

Pyra 2 uses 3 mm filament, while the newer 3FXtrud 20 Uno, 3FXtrud 25 Uno, 3FXtrud 25 Duo, and 3FXtrud 30 Duo use 1.75 mm.