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

CFF operates in this way. The printer uses two print nozzles. 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. This continuous strands of composite fibers inside 3D printed parts adds strength to the built object that is comparable to parts made of metal.

In addition to using composite materials for strong parts, the strategy used to lay down layers can affect part strength. Markforged recommends two strategies: Isotropic Fiber fill or Concentric Fiber fill.

With the Isotropic Fiber fill pattern, layers are unidirectional, similar to what you would find in a traditional laminated composite. The pattern deposits layers in a single angular orientation with 180-degree turns at the edges of the part. This pattern enables printed objects to resist bending in the XY plane. A drawback is that this pattern is fiber and time intensive.

In the Concentric Fill pattern, the print nozzle traces a specific number of shells within the walls of a part. These shells reinforce the walls, enabling the part to resist bending around the Z axis.

With Concentric Fill, users can reinforce:

–the Outer Shell only. This reinforcement only adds concentric rings to reinforce the outer perimeter of the part. This gives the part strength by reinforcing the walls with parallel strands of fiber.

–the Inner Holes only. This reinforcement adds concentric rings around all internal features of the part, which can be used to reinforce holes, cavities, and any other internal features.

–all walls. This setting adds the specified number of concentric rings to both the perimeter of the part and all internal features. This default setting combines the reinforcement strength of both Outer Shell and Inner Hole Reinforcement.

Reinforcing 3D printed parts is an excellent tool to add strength to parts.