Composite 3D Printing: An Emerging Technology with a Bright Future 

Composite 3D printing is a young technology, but one with huge, largely untapped, potential.
 
According to a SmarTech Analysis report, composite 3D printing will grow into a nearly $10 billion business within the next decade – a significant growth opportunity, to say the least.
 
In today’s article, we’ll dive into what benefits composite 3D printing provides, key technologies available on the market, and applications – to find out what drives the growth of this exciting industry. 
 

What is a composite? 

 
Composites typically comprise a core polymer material and a reinforcing material, like chopped or continuous fibre. The composite material offers higher strength and stiffness compared to non-reinforced polymers. In some cases, it can even replace metals like aluminium.
 
These enhanced material properties make composites sought-after materials for tooling and end-use applications in a range of industries, like aerospace, automotive, industrial goods plus oil and gas.
 

What are the benefits of composite 3D printing?  

 
The ability to streamline and cut the cost of traditional composite manufacturing is one of the key factors driving the growth of composite 3D printing.
 
There are numerous methods for fabricating composite components, in addition to 3D printing. However, most of them have a range of drawbacks: the need for the manual layup of the layers of a composite and the use of expensive curing equipment and tooling, like moulds. 
 
This makes the process of traditional composite manufacturing very labour, resource and capital intensive, which means that it can be difficult to scale it to large volumes.
 
3D printing, on the other hand, enables the manufacturing process to be automated, since the entire process is driven by software and requires manual input only at the post-processing stage. 
 

Continuous vs Chopped fibres 

 
In 3D printing, it’s possible to print with two reinforcement types of fibre, chopped and continuous. In the case of chopped fibre, small strands, less than a millimetre in length, are integrated into the polymer material. The percentage of fibre used, and the base thermoplastic determine how strong the final part is.
 
In the case of continuous fibre, long strands of fibre are mixed with a thermoplastic, like PLA, ABS, Nylon, PETG and PEEK during the printing process. Parts 3D-printed with continuous fibre are extremely lightweight, yet as strong as metal.
 
In terms of types of fibres used, carbon fibre is one of the most popular, followed by fibreglass and Kevlar. 
 

Composite 3D printing technologies on the market 

 
In 2020, the market for composite 3D printing remains young, with only a handful of companies offering composite 3D printing solutions. Most 3D printers capable of processing composite materials are based on the polymer-extrusion process, known as Fused Filament Fabrication (FFF). 
 
In FFF, a nozzle is moving above the build platform, extruding a melted thread of plastic, called a filament, and creating an object layer-by-layer. 
 
3D printing of filaments containing chopped fibres is straightforward, only requiring a hardened steel nozzle to resist abrasive fibre strands. However, when it comes to continuous fibre printing, the FFF process will require a second nozzle to separately deposit a single, uninterrupted strand of fibre. 
 

Markforged: a composite 3D printing pioneer 

 
The continuous fibre 3D printing method was first introduced by Markforged in 2014, when the company launched the Mark One. 
 

 
While the Mark One has been replaced by a new generation of 3D printers, the technology remains the same: the printer is equipped with two nozzles, one to lay down plastic filament and the other to simultaneously lay down carbon fibre strands. 
 
Now, in 2020, Markforged offers a range of desktop and industrial composite 3D printers, with main applications in functional prototyping and manufacturing of end-use parts and tooling. 
 

Desktop Metal’s Micro Automated Fiber Placement technology 

 
Desktop Metal is another company that innovated FFF technology to print composites. In a move, quite surprising for a company previously focused solely on metal 3D printing, Desktop Metal launched the Fiber 3D printer in November 2019. 
 
A new polymer desktop system combines a traditional Automated Fibre Placement (AFP) technology with FFF to 3D print parts enhanced by continuous fibre. 
 

 
AFP technology is an automated composite manufacturing process. It involves heating and compacting fibre reinforcements on typically complex tooling moulds to produce continuous fibre composite materials. Desktop Metal scaled this process down to a desktop format, calling its new technology Micro Automated Fibre Placement (μAFP). 
 
The μAFP works like Markforged’s technology, but instead of using spools of fibre, it uses rolls of fibre tape. It can embed carbon fibre into nylon, PEEK and PEKK, and nylon can also be integrated with fibreglass.
 
To create small composite parts, manufacturers still rely primarily on hand layup. Such labour-intensive processes require technicians, expensive tooling and a lot of time, all of which increase the overall cost of manufacturing a part.
 
By combining μAFP with FFF in its new Fiber systems, Desktop Metal aims to make smaller composite parts easier and less expensive to produce. 
 
The Fiber can be used to produce jigs and fixtures, various end-use parts, as well as any components where lightweighting is a priority, such as racing equipment.
 

Anisoprint’s Composite Fiber Coextrusion technology

 
In a similar vein, Anisoprint, the Russian and Luxembourg start-up, has developed an extrusion-based process that the company calls Composite Fiber Coextrusion (CFC). 
 

 
Unlike Markforged’s and Desktop Metal’s technologies, CFC technology enables the reinforcement of plastic with continuous composite fibres directly during the printing process, not at the pre-printing stage. This approach allows users to use any plastic they want (PETG, ABS, PC, PLA, Nylon, etc.) and change composite infill density.
 
Anisoprint’s first machine has been a desktop-format Composer 3D printer. Recently, the company also unveiled the Anisoprint ProM IS 500, the industrial machine designed to print high-temperature thermoplastics with continuous fibre reinforcement. The Anisoprint ProM IS 500 will have up to four changeable print heads for printing composites and pure plastic. With these, it will be possible to reinforce different zones of the part with different composites (e.g. carbon/basalt), depending on the user’s goal. 
 
When the system officially launches at the end of 2020, it will mark yet another step forward, both for composite 3D printing and advanced polymer manufacturing. 
 

Composite 3D printing and robotics 

 
In addition to FFF 3D printing, a few companies have developed an approach which combines composite 3D printing with robotics. Such a combination provides greater flexibility in terms of geometry, since the robotic arm can move along multiple axes, and the possibility of printing larger parts.
 
Arevo is one such company that has developed a laser-based method for 3D printing with carbon fibre. The process involves the deposition of layers of pre-impregnated continuous carbon fibre filament, that is simultaneously heated with a laser, before a roller compresses it onto the build surface. The process resembles the Direct Energy Deposition method, which is typically used with metal. 
 

 
In Arevo’s process, the deposition head is mounted onto a multi-axis robotic arm, making it possible to 3D print in any orientation that best suits the design of the part. 
 
‘When you look across 3D printing, most of 3D printing is layer-based, and the layers are deposited in the X and Y planes. When you look at the properties of parts made with that process, they tend to suffer in the Z direction’, says Wiener Mondesir, CTO at Arevo. 
 
Thanks to using a robotic arm, Arevo has ‘eliminated the Z strength issue that plagues other layer-based technologies because [they] are able to lay down [material] in the Z direction’.
 
Furthermore, ‘robots provide infinite build envelope capability because we can put our robots on the gantry to make aerospace parts. At the same time, the same robot can make a bike’.
 
Arevo has demonstrated the latter point by developing the world’s first 3D-printed composite bike frame. More on this case below. 
 

Continuous Composites 

 
Another company combining composite 3D printing and industrial robots is US-based Continuous Composites. Its method, called Continuous Fiber 3D Printing (CF3D), feeds a roll of dry carbon fibre into a printhead, mounted on a seven-axis industrial robot. Inside of the printhead, the fibre is impregnated with a rapid curing photopolymer resin and then extracted through the end effector and instantly cured with a powerful energy source.
 
Like Arevo, the seven-axis arm allows the fibre to be oriented in any way to create a part that is strong in all directions. Interestingly, since the curing of the resin takes place simultaneously with the extrusion, it allows the CF3D process to print in mid-air, without supports. 
 

Fortify: Combining composite 3D printing with Digital Light Processing 

 
As discussed above, parts 3D printed with chopped carbon fibre are weaker than those made with continuous carbon fibre. However, Boston-based start-up, Fortify, has developed its Digital Composite Manufacturing (DCM) technology, which proves that it’s not always the case.
 
DCM is a novel take on Digital Light Processing (DLP), in which a projector is used to cure a photosensitive resin in a liquid state. In the case of DCM, the liquified resin is mixed with reinforcing additives, such as chopped carbon fibre, that are aligned using a magnetic field during the printing process.
 
‘We have developed a technique that allows us to magnetically orient fibres within a fluid medium. The parts we are printing are essentially the highest resolution composites produced to date. With the magnetic assembly, we’re able to control multiple properties like strength, stiffness, thermal conductivity in three dimensions within each voxel’, explains Fortify’s CEO, Dr Joshua Martin, speaking in an interview with AMFG. 
 
One area Fortify is currently focused on is the development of composite tooling with its technology.
 

 
‘We’re driving heavily into the [injection moulding] market because our tools are able to handle significantly more shots and cycles than competitive solutions.’
 
Last year, Fortify raised $10 million in a Series A funding and struck partnerships with two chemical giants, Royal DSM and Henkel. Considering these milestones, Fortify is in a good position to drive its technology to commercialisation, which is slated for next year. 
 

Impossible Objects 

 
Impossible Objects is another company innovating the field of composite 3D printing. Instead of using extrusion or robotics, the company has developed an entirely unique approach.
 
In the process, called Composite-Based Additive Manufacturing (CBAM), sheets of fibre reinforcement material, such as carbon fibre, are passed beneath an inkjet printhead, which deposits a liquid solution onto the sheet, in that layer’s shape. 
 

 
Then, a layer of polymer powder is deposited onto the sheet. The powder sticks to the areas where the liquid was deposited. The excess powder is blown or vacuumed off. This is repeated layer-by-layer until the object is complete as a stack of sheets.
 
This stack is then compressed and placed into an oven, which fuses the thermoplastic powder, resulting in a fibre-reinforced thermoplastic composite.
 
Because of using inkjet printing, the CBAM method is much faster than extrusion processes, and there’s also the possibility to print large parts. Impossible Object’s latest 3D printer, the CBAM-2 launched in 2019, can 3D print parts using sheets of 12 in x 12 in (around 30 cm x 30 cm) in size.
 
The CBAM-2 can currently work with PEEK and Nylon 12 thermoplastics and long fibres made from carbon or fibreglass. More materials, including Nylon 6 and elastomers, are underway. 
 

Composite 3D printing applications 

 
Applications for composite 3D printing are running the gamut, from prototyping to tooling and end-use part manufacturing.
 

Using composite 3D printing for large blade tooling

 
In the aerospace industry, producing tooling can be a long and expensive process. Looking to overcome these challenges, American aerospace manufacturer, Bell Helicopters, turned to Thermwood to produce large moulds for helicopter blades.   
 

 
Thermwood is a US-based manufacturer that has developed Large Scale Additive Manufacturing (LSAM) technology capable of printing large composite tooling. One of the unique features of Thermwood’s LSAM 3D printer is its hybrid approach to producing parts, combining additive and subtractive technologies.
 
Coming back to Bell, the company required a large composite tooling with good surface finish, tight tolerances and the ability to withstand autoclave processing — a technique which helps to strengthen composite parts that will be exposed to elevated pressure and temperature.
 
LSAM was ideal for such an application for two main reasons. First, it allowed the 6 m long tool to be manufactured from a high-performance carbon-reinforced PESU material, which can withstand high pressures and temperatures. Second, since LSAM is a hybrid technology, a part can be 3D printed and finished without the need for a second machine — helping to further speed up the production process.  
 
These benefits enabled Thermwood to manufacture the tool in just a few days, as opposed to the months it would take with traditional processes.
 
This achievement points to the new possibilities that large-scale composite 3D printing unlocks for large and technically complex aerospace components.
 

Wärtsilä 3D prints composite lifting tool

 
Wärtsilä, a company which specialises in marine and energy markets, applied a composite X7 3D printer from Markforged to manufacture a lifting tool. The tool is a custom piece of hardware that allows the team to move immensely heavy engine parts, such as pistons. 
 
The company used to machine such tools out of solid steel but found the process too expensive and opted for 3D printing a polymer lifting tool reinforced with carbon fibre. The resulting tool was 75 per cent lighter while capable of lifting 960 kg. Wärtsilä believes that it saved €100,000 in tooling alone by switching to composite 3D printing. 
 
This example also illustrates the possibility of replacing heavy metals used to manufacture a part, with lighter, but equally strong, composite materials. 
 

Composite bike frames

 
Bike frames are one of the most successful applications of composite 3D printing in end-use part manufacturing. Bike frames made of carbon fibre are becoming increasingly popular, as the material’s properties are well-suited to frame construction. The material is strong, durable and lightweight, which makes it a highly sought-after alternative to metal bike frames.
 

 
However, carbon fibre frames have two major drawbacks: the material is extremely expensive, and the manufacturing process is notoriously labour-intensive.
 
Arevo is overcoming these challenges head-on, using its robotic 3D printing process. The company’s approach creates a frame uniformly strong in all three dimensions. This feature differentiates Arevo’s technology from traditional filament 3D printing, where 3D-printed parts tend to be anisotropic when first printed, meaning they are not equally strong in all directions.
 
Thanks to this technology, Arevo says it can produce carbon fibre bikes at a competitive cost of $300, compared to similar traditionally manufactured bikes, which have an average price range of between $1000 to $2000.
 
The start-up is already partnering with a few bike companies, including Franco Bicycles and Pilot. 
 
With composite bike 3D printing gaining traction, Arevo’s technology is adding a new dimension to the bike manufacturing sector.
 

Composite 3D printing: Pushing the limits of composite manufacturing 

 
Despite being a young technology, composite 3D printing is gaining a stronger foothold within the manufacturing industry. It offers a faster and more automated approach to producing composite parts, which for a long time have been handmade. 
 
Composite 3D printing helps in rethinking the material choice for certain applications, allowing manufacturers to replace metal with durable, cheaper plastic. Finally, it helps to make the process of manufacturing composite parts less expensive. 
 
Combined, these benefits suggest that composite 3D printing will only be growing and maturing to become a standard method in the composite manufacturer’s toolbox.