3D Printing Material Spotlight: Stratasys FDM Nylon 12CF

Stratasys recently released a new offering in it’s FDM Nylon material family. This new material is a carbon-filled thermoplastic called Nylon 12CF. To showcase some of the features of this great product, we have put together Nylon 12CF FAQ, features, usage tips and best practices information. Continue reading to learn more about this exciting new material.

What is a Nylon 12CF and why did Stratasys create it?

Nylon 12CF is a thermoplastic material that has added fibers to improve or alter its material properties. These fibers are used to improve the strength, stiffness and thermal properties of injection molded parts. Glass and carbon fiber are most typically used, but many other materials can be used to improve other properties such as stability and wear resistance.

Stratasys carbon-filled Nylon 12CF is filled with chopped carbon fiber at a loading of 35% by weight. This makes it much stiffer than regular Nylon and closer, in terms of strength and stiffness, to ULTEM. The combination of carbon fiber and Nylon 12 provides material with a very high strength-to-weight ratio, which is ideal for applications where strength and optimized (reduced) weight is important. Often, materials such as aluminum or other metal alloys are used over thermoplastics due to the costs of injection molding when, from a material property perspective, a thermoplastic is acceptable. Using Nylon 12CF we can now achieve the required strength and achieve a part with significantly less weight.

As shown in Figure 1 below, the fibers in the filament are oriented in the direction of extrusion, which means the material properties are well defined and consistent throughout the material – and as such, this material is considered a composite. It is important to note that the carbon fibers exist within the layer and do not cross between layers so the additional strength is only in the XY plane (or within layers) and not in the Z direction (or between layers). This creates a material with anisotropic properties, which means that it has different material properties in different directions. Due to this material characteristic, you will note going forward there are two values for material properties, such as tensile strength and flexural strength, one for directions in the XY plane and one for directions in the Z axis. All FDM printed materials should be considered anisotropic due to the layers which also create different strengths for directions in Z versus the XY plane, but for Nylon 12CF the difference is much greater.

Figure 1: Top down view of the filament cross section showing the fiber alignment in the direction of extrusion.

How does it compare to other materials?

As a key characteristic for the development of Nylon 12CF is its high strength-to-weight ratio, we will look at flexural (or bend) strength and tensile strength. Flexural strength a good measure of the stiffness of the material and is defined as ‘its ability to resist deformation under a bending load’ and tensile strength is defined as ‘its ability to resist being pulled apart’, together they are a good measure of a materials stiffness and strength. These properties are tested as shown in Figure 2 and, as mentioned earlier, due to the anisotropic nature of this composite it is required to be characterized in the XY plane as well as the Z direction. We will also look at the specific gravity as this is a measure of the density of the material and ultimately its weight.

Figure 2: Flexural and tensile testing performed in Z direction and XY direction.

Looking at Table 1 below we can see that the XY flexural strength (stiffness) and tensile strength for Nylon 12CF is now ~2X greater than unfilled Nylon 12 and approximately the same as ULTEM. When comparing the strength and stiffness of Nylon 12CF between the XY plane and Z axis, the anisotropic influence of the carbon fiber can be seen as the material has double the strength and stiffness in the XY directions as it does in the Z direction.

Table 1: material property comparison

We can see that both the stiffness and the strength of Nylon 12 and Nylon 12CF are essentially the same in the Z direction as the fibers do not link across layers but only through the layers.

We can also see the anisotropic nature of FDM material shown in the difference between the XY stiffness (21000 PSI) and Z stiffness (11100 PSI) for ULTEM. This anisotropic behaviour is a result of the layers produced during printing and shows the difference in strength within layers (the strength of the plastic) versus the strength between layers (adhesion strength). For additional material property information reference the following documents:

• Nylon 12 data sheet
• Nylon 12CF data sheet
• ULTEM data sheet

Why not just use ULTEM?                            

Nylon 12CF is about as strong and stiff as ULTEM and doesn’t have the improved temperature and chemical resistance capabilities so why wouldn’t I just use ULTEM? It comes down to strength-to-weight ratio. If you are building parts for manufacturing jigs/fixtures or for any automotive or aerospace application, weight is a critical factor.

We can see that the SG for Nylon 12CF is 1.15 vs 1.27 for ULTEM, this means that for the same part printed out of Nylon 12CF will result in a 10% decrease in weight compared to an ULTEM part. This is a significant reduction in weight for a part with approximately the same strength.

How can I get it?

Nylon 12CF is available for the Fortus 450mc FDM 3D Printer and requires a service person to install the upgrade kit. This is approximately a four-hour installation. The upgrade comes with two material drive blocks, a material y block and a new head. The new components are made with titanium. The head needs to be changed when going between Nylon 12CF and any other material so there is a docking station that comes with the kit to store the unused head when it is not in use (see Figure 3 below).

SR-110 (Fortus Plus) is used for support material. Note that this is a soluble support so a wash station is required to soak the parts in to dissolve the support material away. The wash stations contain a sodium hydroxide solution that is heated and agitated to dissolve the support material quickly. Refer to the linked document in the build considerations section below for specific instructions on removing support material. Contact Javelin for Nylon 12CF upgrade kit pricing.

Figure 3: Docking station to store unused head

What are the key build considerations?

Like most engineering grade FDM thermoplastics, there are specific processing and build requirements to ensure the best surface quality, strength and build reliability. There are recommendations regarding build orientation, slice height, support style, infill styles, use of sacrificial towers, build mode and toolpath parameters that should be followed. Reference this document to get specific information on these parameters.

The most important thing to remember is that the material is anisotropic so a good understanding of the applied loads and bending applied to the part is necessary to properly orient the part to ensure the strength is in the required direction. Another good rule of thumb is to try to orient your part to achieve the most surface area between layers.

As always, it is critical to ensure that a good XYZ offset calibration was completed after switching material to Nylon 12CF. Take the time to get XY into specification (+/- 0.002”) before doing the Z calibration. When doing Z make sure to use calipers and try to get it within +/- 0.001”.

What are the applications?

• Robotic end effectors (end-of-arm-tooling) – End of arm of tooling is very specific to the part that is being molded and so the requirements change often. They are also typically required in low volume, so it’s an ideal application for 3D printing. Traditionally this tooling is machined out of aluminum, but with Nylon 12CF a much lighter tooling can be made resulting in the ability to use a smaller-class, lower-cost robot. As can be seen in Figure 4 below the freedom of design offered by 3D printing also allows the design of a much simpler tool, resulting in significant weight and complexity reduction.

Figure 4: Traditional EAOT versus simplified FDM component using design for additive manufacturing methodologies.

• Metal Forming – Metal forms have been successfully 3D printed and used in the sheet metal industry for a while now. 3D Printing allows anybody to manufacture these tools and is much quicker and cheaper than traditional CNC machining out of metals. Because Nylon 12CF has such improved wear resistance due to the carbon fiber it is expected that these forms will last even longer.

• Jigs/Fixtures/Drill Guides – The high stiffness and light weight of Nylon 12CF make it ideal for jigs and fixtures. This rigidity also makes it a good choice for drill guides – resulting in better accuracy of drilled holes. Also, the stiffness allows the fixture to be a conformal surface when the part has inherent flexibility, eg., light-gauge sheet metal. See Figure 6 for an example of drill jig with metal inserts.

Figure 6: Drill guide with metal inserts printed out of Nylon 12CF

• Bracketry – Lightweight, stiff FDM Nylon 12CF brackets can replace metal brackets in an industrial setting and is especially beneficial for brackets of moderate to high complexity that would require multiple components or difficult machine setups due to part geometry.

Figure 7: Custom tooling brackets by ORBITAL ATK designed for flexibility and rapid response to project requirements. FDM Nylon 12CF provides the necessary strength and stiffness.

If you are interested in upgrading your Fortus 450mc 3D Printer to take advantage of this amazing material, or would like a benchmark printed, please contact the 3D Printing experts at Javelin and we would be happy to help!