Types of Nylon Used in FDM 3D Printing

Nylon, also known as polyamide (PA), is a family of thermoplastic polymers valued in FDM 3D printing for their strength, flexibility, and wear resistance. Despite their appealing mechanical properties, nylon filaments are among the most challenging materials to print due to their high printing temperatures, tendency to warp, and strong affinity for moisture. Several nylon types are formulated for FDM printing, each with distinct characteristics that influence print quality, mechanical performance, and ease of use.

PA6 (Nylon 6)

PA6 is one of the most common nylons used in FDM printing. It is a tough material with high tensile strength and excellent impact resistance, making it suitable for functional parts and mechanical components. However, PA6 absorbs moisture quickly from the air, which can lead to bubbles and poor layer adhesion if not properly dried. It also has a strong tendency to warp unless printed with a heated bed and enclosed chamber. Typical extrusion temperatures range from 250°C to 270°C. After annealing, PA6 parts gain improved dimensional stability and heat resistance due to increased crystallization.

PA66 (Nylon 66)

PA66 is similar to PA6 in composition but has a slightly higher melting point, around 260°C. This gives it superior stiffness, wear resistance, and heat resistance compared to PA6. It exhibits low creep under load and performs well for precision mechanical parts. Like PA6, PA66 is highly hygroscopic and prone to warping during printing, so it requires dry filament storage, a heated bed (around 80°C–100°C), and an enclosure. The material hardens considerably after annealing. However, when exposed to humidity afterward, it becomes more ductile and impact resistant.

PA12 (Nylon 12)

PA12 is a common engineering-grade filament that differs from PA6 and PA66 through its longer molecular chain and lower moisture absorption. This makes it more dimensionally stable and easier to print with fewer warping issues. Its typical extrusion temperature ranges between 240°C and 260°C. PA12 provides high impact resistance, very good chemical resistance, and greater flexibility than other nylons. Its lower water absorption also means it retains dimensional accuracy longer in humid environments. PA12 is heat resistant to around 180°C and responds well to annealing for further crystallization and toughness.

PA612 (Nylon 612)

PA612 combines characteristics of PA6 and PA12. It offers lower moisture absorption than PA6, while maintaining greater stiffness than PA12. The result is a material well-suited for applications requiring balanced mechanical strength and stability. It is easier to print than PA6 or PA66 and less prone to warping. PA612 parts have smooth surfaces and are less brittle, making them versatile for both aesthetic and functional components. Heat resistance is moderate, generally below PA66 but above PA12.

Other Nylon Blends and Composites

Some nylon formulations blend multiple polyamide types or include additives to target specific goals. Fiber-reinforced nylons are especially popular: carbon fiber and glass fiber reinforcements enhance stiffness, strength, and dimensional stability while reducing shrinkage and warping. These additives also improve surface finish by limiting thermal deformation during printing. However, fiber-filled filaments are more abrasive, requiring hardened nozzles.

Printability Challenges

Printing nylon successfully requires high extrusion temperatures (typically 240°C–280°C), a heated print bed, and controlled ambient temperatures (so long as not printing with Polymaker nylons). Nylon’s natural hygroscopicity causes moisture absorption, which can create steam pockets during extrusion, leading to surface pitting and weak layer adhesion. Filament should always be kept dry, ideally in a sealed container or a filament dryer. Warping is another major difficulty, as nylon contracts strongly during cooling.

To address warping, Polymaker has developed Warp Free Technology, which optimizes the material formulation to relieve internal stress during cooling. This allows larger nylon parts to be printed on open-frame printers with reduced risk of curling or layer separation.

Effects of Annealing and Moisture

Annealing nylon parts enhances their crystallization, increasing structural strength, stiffness, and heat resistance. Fully crystallized parts perform better under load and at elevated temperatures. Over time, however, when parts absorb moisture, the polymer chains become more mobile, resulting in higher ductility and impact resistance but less rigidity. This tradeoff makes nylon applications adaptable for parts requiring toughness and slight flexibility.

Summary

Each nylon type brings a different balance between ease of printing, mechanical performance, and environmental stability. PA6 and PA66 provide high rigidity and heat performance at the cost of more challenging print behavior, while PA12 and PA612 are more forgiving and moisture-resistant. Reinforced nylons further address warping and mechanical limits. With proper drying, temperature management, and the use of advanced formulations like Warp Free Technology, nylon remains one of the most capable materials for producing durable, functional parts in FDM 3D printing.