This article talks about the benefits of using 3D printing technology, where long fiber filaments are embedded in the filament and make the printed part stronger.
The range of materials available in 3D printing, even in molten deposition modeling, has grown exponentially in the past few years. Not only are there many reputable brands that carry a variety of thermoplastics such as ABS, PLA, Nylon, and PETG, but there are also compounds of all of these with different particles/filaments embedded in them, such as carbon fiber and fiberglass. There is another type of composite 3D printing that is becoming increasingly popular: continuous fiber.
Chopped vs. Continuous
In the standard fiber-filled process, strands of fiber are cut into very short pieces to create a printable material. The most obvious drawback of this method is that there is little overlap between fibers and almost no fibers passing through adjacent layers. As such, parts printed with fiber-filled materials are usually only marginally stronger or more rigid than traditional 3D printed parts.
Continuous fiber 3D printing is exactly what its name says. Instead of incorporating millions of half-millimeter strands of fiber into the warp during manufacturing, a spool of fiber is used to fit very long strands of fiber into the parts being printed. Continuous 3D printing of the fibers provides greater strength and rigidity because it better mimics the traditional carbon fiber part-making process, in which long strands of fiber are layered on top of resin.
traditional carbon fiber costs
Traditional carbon fiber parts are expensive not because of the cost of the raw materials but because of the cost of the equipment needed to transport and process that material. Pre-preg is a term applied to a composite of carbon fiber and resin that is still wet and ready to be molded. It has to be refrigerated and frozen from the moment it’s produced until it’s used, which means there’s a lot of logistical expense involved. To make carbon fiber parts, molds must be made first, which is of course not free. Handling finished parts requires autoclaves the size of the parts themselves, and given that carbon fiber is a popular choice for aircraft manufacturing, autoclaves would be much more expensive to build and operate, especially in this industry.
With continuous fiber 3D printing, nearly all of these costs are eliminated without compromising strength. There are many companies offering continuous fiber 3D printing, but here we are looking for three well-known brands.
Markforged has many machines which can draw continuous fiber. Their systems rely on a separate tool to insert the different materials: One extrudes a thermoplastic matrix just like a conventional 3D printer, while another inserts strands of fibers in specific areas to increase tensile strength. They can work with carbon fiber, fiberglass and Kevlar.
The Desktop Mineral Fiber System works very similar to the Markforged solution except Micro Automated Fiber Placement (μAFP) technology uses rolls of fiber tape instead of fiber spools. Carbon fibers can be embedded into nylon, PEEK and PEKK, and nylon can be combined with fiberglass. They claim their parts can be stronger than steel and lighter than aluminum.
Continuous Vehicles takes a different approach with their CF3D solution. Instead of using a thermoplastic for a solid material, it uses a photopolymer. The tool head coats the fiber strand with a photopolymer which is deposited and then immediately cured with strong UV light. This allows you to include each individual line with the fibers, rather than just defining areas. Continuous fiber 3D printing is exactly what its name says. Instead of incorporating millions of half-millimeter strands of fiber into the warp during manufacturing, a spool of fiber is used to fit very long strands of fiber into the parts being printed. Continuous 3D printing of the fibers creates greater strength and stiffness. This also means that it can bridge long gaps without the need for backing. The CF3D system is compatible with structural fibers such as carbon, glass, and aramid, as well as functional fibers such as optical and metallic fibers, and enables the use of a variety of interesting tricks such as sensors and integrated circuits.
While these systems are not as affordable as most desktop 3D printers, they are more accessible than most metal 3D printers. Carbon fiber fabrication equipment is common and easy to use. Overall, the selection of materials for this sector will continue to grow with the 3D printing materials sector. More polymers will be created for the matrix and more fibers will be introduced to match. I wouldn’t be surprised if there are now materials scientists developing fibers that expand or contract when heated or exposed to electricity, much to the delight of those working on soft robotics and embedded electronics.
As mentioned, 3D printed fiber reinforced plastics are a cost-effective way to 3D print strong, durable parts that look a lot like metal parts. In general, this process is much cheaper than 3D printing of metals, as selective laser sintering (SLS) or selective laser melting (SLM) is. The addition of fiber filaments adds resistance unprecedented to traditional printing methods.
Markforged, based in Massachusetts, is one of the most successful companies to date that has used such technology in 3D printers. Critics praised the printers of this company’s first and second models. Both printers 3D print hardware using iron, carbon fiber and other stiffeners in addition to plastic.
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