Materials for 3D printing – Nylon (PA6, PA12)

The trend of taking over materials by 3D printing technologies, so far associated only with industry, continues. Thanks to it, new, industrial 3D printers adapted to work at high – and, importantly, constant temperatures – appear on the market. One of the materials that has been gaining more and more popularity in recent years is Nylon – previously used only as a material for production in powder technologies, now it also functions in the form of filaments more and more often.

Let’s start with the nomenclature. Nylon is a trade name for polyamides by the chemical company DuPont. Another name you may come across is the name PA. Usually, it is written with numbers – the most common types of polyamides found in 3D printing are PA 6 and PA 12 and it comes from a chemical compound from which nylon is synthesized. These materials differ from each other.

What attracts the attention of representatives of the 3D printing world to nylon materials are their great material properties. Nylon is characterized by high mechanical, thermal and fatigue strength (low coefficient of friction), which makes it suitable for technical applications. Resistant to less aggressive chemicals.

This material can be used to create highly loaded structural elements such as tools, hinges, clamps, gears, functional prototypes or mechanical parts. It is also used in specialized applications for the automotive, aviation and military industries.

Nylon-based materials are characterized by a high melting point, therefore the production of 3D models from them should be carried out at a constant, elevated temperature. The material is also highly hygroscopic, meaning it easily absorbs water from the environment. On the one hand, it allows easy coloring of elements made of this material – on the other hand, it can make 3D printing from nylon troublesome.

Polyamide materials are used to produce 3D prints in various technologies – SLS, MJF and FDM.

SLS

In SLS 3D printing, nylon is in the form of a powder, which is selectively sintered with a laser beam. The most commonly used material is polyamide PA12 powder, which allows for the production of functional elements, and PA11, which is characterized by higher tensile strength.

Powder technologies are the most appropriate 3D printing method with PA12 and PA11, because they allow for a constant, high operating temperature, which is especially important in the case of nylon-based materials. The SLS technology allows for the production of durable elements with a slightly rough surface, cost-effective in low-volume production.

MJF

The Multi Jet Fusion HP technology currently allows 3D printing from three types of polyamide-based materials:

• PA11 – the most often used material for industrial applications. Thanks to its properties, it is suitable for the production of functional elements.
• PA12 – the most popular material for 3D printing in MJF technology. Used for 3D printing of functional and consumer parts. Produced elements are strong and durable, and at the same time show sufficient flexibility to be resistant to cracking. The material from HP is biocompatible and meets the RoHS directive standards.
• PA12GB – material enriched with glass balls (40%), thanks to which it exhibits higher stiffness than PA12. Its properties position it as a material for making durable elements resistant to friction and wear over time.

FDM

The growing range of PA6-based materials for 3D printing in FDM technology encourages making your own prints. When working with nylon-based materials, it is particularly important to store the material and handle it in the pre-3D printing stage.

The high hygroscopicity of the material does not facilitate the 3D printing process. In practice, the material on the spool can absorb water up to 10% of its own weight. Due to this fact, always store the spool of material in an airtight container with silica gel to absorb moisture.

But how does one know if the material has absorbed water? The first determinant is of course its increased weight. The second – the noise it makes while heating up in the head. When the material absorbs moisture, it begins to click characteristically with raising its temperature to the melting point. Then, instead of smooth, 3D printed layers, we get a jagged surface, which disqualifies the print both in terms of aesthetics and its mechanical properties.

Then, the filament should be subjected to high temperatures, using a special dryer or … your own oven. However, it takes time (4-6 hours), and due to our own safety, we recommend heating the filament in dedicated devices.

The most problematic issues with nylon 3D printing are material lifting from the printing bed and deformation due to shrinkage. To prevent it, ensure a constant temperature in the working chamber of the 3D printer and avoid sources of cold air (e.g. air conditioning).

How much does a nylon-based filament cost?

Estimated prices for various types of polyamide-based materials:

Manufacturers offer nylon materials enriched with carbon fiber or glass beads to provide improved mechanical properties of 3D prints. This is usually associated with an increased price.