Continuous Fiber Fabrication (CFF) is a term coined by Markforged for the material and 3D printing process it developed.

In CFF a printer uses two print nozzles to deposit printing material. One nozzle operates like a typical extrusion process; it lays down a plastic filament that forms the outer shell and the internal matrix of the part. The second nozzle deposits a continuous strand of composite fiber (made with carbon, fiberglass, or Kevlar) on every layer. The continuous strands of composite fibers inside 3D printed parts add a strength level to the built object that is comparable with parts made of metal.

The inlaid fibers laid down help deliver such properties as high stiffness, toughness, strength, and heat deflection. Let’s take a look at three of these properties:

Metal strength
The strength of a fiber-reinforced part comes from the combined strength of the plastic and the continuous fiber strands woven throughout the part. This can make parts comparable to aluminum in strength and stiffness.

Durability
Reinforcing fibers can increase the lifetime of a part. These fibers strengthen the part to hold up better over extended periods of time. These parts usually show a longer life than standard plastic parts.

Optimized properties
Designers can select which areas of a part to reinforce, in effect tailoring the part’s strength to the application.

(some of this information is from a white paper from Markforged on working with composite materials.)