Out of Stealth Mode: Versatile Continuous Carbon Fiber 3D Printing
Michael Molitch-Hou posted on May 20, 2019 |

As we recently explored, the field of carbon fiber 3D printing is developing at only a slow pace. There are a few companies and research endeavors pursuing robust carbon fiber 3D printing technologies, but even fewer have actually come to market. That may still not change for a year or two, but when it does, the variety of systems might be quite exciting.

This will be in part to the commercialization of one of the earliest yet least known carbon fiber 3D printing platforms in the industry. Developed by Idaho-based Continuous Composites, Continuous Fiber 3D Printing (CF3D) combines carbon fiber reinforcement with thermoset polymers and industrial robotics to 3D print in ways yet seen by the additive manufacturing (AM) space.

To learn about the technology and the company, engineering.com spoke to CEO Tyler Alvarado.

What Is Continuous Fiber 3D Printing?

To understand how CF3D works, we have to understand how carbon fiber reinforced polymers (CFRPs) are created. Dry carbon fibers are typically run through a resin bath to the point of saturation. This pre-impregnated material (prepreg) is then spooled and sent to a customer. From initial storage to shipment to storage at the point of end use, the prepreg must be kept in frozen conditions until it’s ready to be thawed, unrolled, sliced and applied to the object it’s meant to reinforce. This prepreg process significantly increase the cost of the raw materials used in traditional composite manufacturing techniques.

Alternatively, CF3D begins with a roll of dry fiber, which is fed into a printhead mounted onto a seven-axis industrial robot. Within the printhead, the fiber is impregnated with a rapid curing resin before it is pulled through the end effector and cured instantly, using a high-intensity energy source at the point of deposition, to create a 3D object. 

The robotic arm on the left includes the printhead, which pre-impregnates the reinforcement fiber with rapid-cure thermoset plastic that is instantly hardened as it is deposited on the print platform hosted by the robotic arm on the right. (Image courtesy of Continuous Composites.)
The robotic arm on the left includes the printhead, which pre-impregnates the reinforcement fiber with rapid-cure thermoset plastic that is instantly hardened as it is deposited on the print platform hosted by the robotic arm on the right. (Image courtesy of Continuous Composites.)

Already at this point in the description of the process, CF3D has demonstrated an important advantage over traditional CFRP manufacturing. Because the technology relies on dry fiber, there is no need for the costly maintenance of prepregs at cold temperatures, potentially reducing the end cost of fabrication.

Because carbon fiber is anisotropic, the orientation of the fibers determines the direction in which a CFRP will be strongest. Using Continuous Composites’ software, the robotic arm can deposit the material in a way that optimizes the orientation of the material for maximum structural strength.

This not only exploits one of the key features of carbon fiber, but also addresses a notorious problem in 3D printing, particularly with regard to fused deposition modeling (FDM). FDM is well known for its weakness in the Z-axis, due to the fact that layers are stacked and not perfectly bonded in the Z direction. Because CF3D features seven degrees of freedom (with more coming according to Alvarado), the printer can compensate for potential z-axis weakness by changing the orientation of the printhead.

“We’re not just limited to just stacking two-dimensional slices. We have the ability to print true three-dimensional objects using any anisotropic fiber,” Alvarado said.“We’re taking designs out of traditional CAD software; it comes into our workflow where we perform a unique structural finite element analysis [FEA] and then generate a sequential continuous fiber toolpath to print the object using continuous fiber.”

Other benefits over traditional CFRP manufacturing include a reduction in manual labor and material waste, since the CF3D is automated and fabricates objects at net shape. This further reduces the costs of what is otherwise an expensive process. Whereas the aerospace industry can afford the high costs associated with carbon fiber reinforcement, as every bit of weight reduction leads to savings in fuel costs, industries that are less prosperous can’t afford to use carbon fiber composites.

Like other existing and yet-to-be-released carbon fiber 3D printing technologies, CF3D is capable of fabricating with more than just carbon fiber. The reinforcement materials are being worked out with material suppliers. So far, they include: carbon, fiber glass, Kevlar, continuous copper wire, continuous fiber optics, nichrome wire and silicon carbide.

This part includes copper wire for embedded circuitry, nichrome wire for heating, and fiber optics for embedded sensing. (Image courtesy of Continuous Composites.)
This part includes copper wire for embedded circuitry, nichrome wire for heating, and fiber optics for embedded sensing. (Image courtesy of Continuous Composites.)

These last fibers have important implications for producing functional parts right out of the printhead. Using copper wire, electronics can be powered as a part of a printed composite structure. Fiber optics allow the part to sense and collect data about itself in real time, for health monitoring or performance optimization. Nichrome can be used to generate heat for anti-ice applications. Silicon carbide is useful for high heat applications.

To print a complex object with multiple types of reinforcement or functional fiber, CF3D currently relies on automated tool changing, with different printheads loaded with different fibers or resins. The company is also developing solutions for adding and dropping fibers in situ.

The resins themselves are being developed in conjunction with potential customers based on the needs of specific applications. For instance, for a structural component for a vehicle, the company has developed a tough, UV-resistant plastic with a high glass transition temperature. For a part that will be installed on the interior of an aircraft, Continuous Composites has developed a resin that meets the smoke, fire and toxicity requirements of the Federal Aviation Administration.

Where Did Continuous Composites Come from?

Though the company has been in existence since 2015 and the technology’s inventor, Ken Tyler, filed its first patents in 2012, Continuous Composites only recently came out of stealth mode. Tyler had experience in the composite manufacturing industry, specifically for marine applications, and understood the manufacturing constraints. He also had experience with stereolithography and understood the size and material limitations of the technology.

“In 2012, he was working in the boat industry and stabbed himself on a strand of cured fiber glass sticking out of a boat hull and had this ah-ha moment,” Alvarado relayed.“[Tyler thought], ‘Wow, these materials are so strong and lightweight. Why are we not using these in the 3D printing industry?’”

According to Alvarado, the firm’s foundational patents cover 3D printing with at least one continuous fiber and one liquid resin, regardless of the type of fiber or plastic. So far, it has received 16 granted patents on the tech, with 250 concepts covered provisionally and 97 non-provisional patent applications in the works. Continuous Composites has also filed patents internationally, as well.

The company is currently involved in partnerships related to three separate components of the business: hardware, software and materials. In addition to the materials partnerships mentioned earlier, the firm’s software is being developed in conjunction with Spatial, owned by Dassault Systèmes. For the hardware, “in addition to our internal resources, we have several strategic collaborators involved in developing our motion platform, controls and printhead. This is all being developed for our customers who are leaders in aerospace, defense, marine, energy, motorsports, construction and sporting goods” Alvarado said.

“They are engaged on a level where they’re providing funding to ensure we focus our R&D efforts to develop the technology for their specific applications,” Alvarado said. “The plan is to get the tech to a stage where we’re ready to sell it to them. We will be selling the machine, both the motion platform and the end effector, selling our software as a service to control the machines, and setting up a good, reliable supply chain for the materials.” 

So far, most of the firm’s funding has been garnered through private investment, in part through a sister company owned by Sandoval. However, strategic partners, customers, angel investors and venture capital firms will be participating in a funding round that will take place in the coming month.

Products will be available both via standard offerings and solutions tailored specifically to given customers. Alvarado believes that the technology will be available to the public in 18 to 36 months.

As news comes out about these investments and product releases, engineering.com will stay on top of the announcements. To learn more about Continuous Composites, visit the company website.

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