A Look Into Continuous Fiber Manufacturing (CFM)March 27, 2021 by Sara McCaslin
CFM, or continuous fiber manufacturing, is a patented form of additive manufacturing that adds continuous fiber reinforcement to components as they are built up.
The CFM method allows for high levels of weight and strength optimization that cannot be achieved with traditional 3D printing methods.
Figure 1. +LAB building a bike frame using CFM. Video used courtesy of +LAB
This article will introduce CFM, how it’s different from traditional 3D printing, as well as its benefits, materials, and applications.
What is Continuous Fiber Manufacturing (CFM)?
CFM combines high-performance and customized load paths (possible with composite materials) with additive manufacturing to generate highly complex geometric components using CAM (computer-aided manufacturing) technology.
More specifically, CFM refers to a method patented in 2015 by moi composites located in Milan, Italy. The company is a spin-off of a collaborative 3D printing called +LAB, located at Politecnico di Milano.
Figure 2. Multidimensional CFM layup of a BMX bike frame using glass fiber and UV cure resin epoxy. Image used courtesy of +LAB
CFM is achieved by using a six-axis robot arm (such as KUKA and Comau robots) outfitted with the necessary tooling to lay continuous fiber, deposit and cure the matrix material, as well as to apply pressure and cut the fibers.
How is Continuous Fiber Manufacturing Different From 3D Printing?
CFM prints both fiber reinforcement and polymer matrix material to create composite parts through the automated layup of reinforcing fibers and the matrix material in a deposition process similar to 3D printing.
There is, however, a key difference: Unlike 3D printing, where the components are built up layer by layer, CFM uses a six-axis robot. The robot additively manufactures the components in multiple dimensions to lay the continuous fibers along non-linear axes.
Benefits of Continuous Fiber Manufacturing
One of CFM’s key benefits lies in its ability to optimize both the weight and structure of a component. An excellent example of this lies in the bike frame shown in figure 3, which achieved a 40% reduction in weight while still maintaining the necessary strength and stiffness to effectively serve as a BMX bike frame. Strength and stiffness are obtained through the layup of the continuous glass fibers embedded in the UV curable resin epoxy.
Figure 3. This BMX bike frame was manufactured using CFM technology, where the combination of directional fibers and UV cured epoxy reduced the weight without compromising strength and stiffness. Image used courtesy of Autodesk
CFM could also work well for one-of-a-kind products, such as a medical prosthesis designed for a specific user’s needs. With CFM, there are no expensive molds or tooling that need to be changed from product to product.
CFM is not used solely for working prototypes but also for fully operational final products.
Materials Currently Utilized in Continuous Fiber Manufacturing
Because CFM creates fiber-reinforced composite materials, there are two types of media present in the components: reinforcing fibers and polymer matrix. Currently, the polymer matrix materials in use are thermosets, including UV cure resin, acrylic, and vinyl ester.
Using a thermoset enables the CFM components to have higher operating temperatures than parts made from thermoplastic materials manufactured using processes such as injection molding or compression molding.
Figure 4. Different layouts of the fibers correspond to different elastic behaviors of the structure. The central part is more elastic while the connections with trucks are reinforced. Image used courtesy of Autodesk
As of right now, the primary reinforcing materials used are continuous glass fiber, basalt fiber, and carbon fiber (which also serves as an electrically conductive fiber).
Applications for Continuous Fiber Manufacturing
Moi has demonstrated various applications for the CFM process, including a BMX bike frame, lower leg prosthesis explicitly engineered for running, the “world’s first” 3D-printed fiberglass boat, and skateboard decks. Their first major CFM project, however, was a fiberglass (glass-epoxy) propeller blade. By nature, propeller blades involve a complex, high-precision geometric design that poses challenges.
Many different markets can benefit from the CFM process, including marine, aerospace, automotive, biomedical, robotics, oil and gas, automation, and manufacturing. CFM is fit for manufacturers that need to develop one-of-a-kind or highly customized parts with greater strength, operating temperatures, and/or control over structural properties than possible with more traditional additive manufacturing methods.
In addition, in a manufacturing setting, CFM can also be used for applications requiring high-performance, unique components (including specialized tools or jigs). It is a manufacturing method for parts that need to be extremely strong and/or stiff, but also weight-optimized, which can be essential in industrial automation.
CFM is a fascinating additive manufacturing method from moi composites that goes beyond both automated composite layup and 3D printing. While it shares much with 3D printing, it is a distinct method that provides greater control over and optimizes material properties while supporting the manufacture of highly complex geometries.