A short overview of composite 3D printing
Generally speaking, “composites” defines a material composed of two (or more) different immiscible components but which properties complete one another. (A composite material is a combination of two materials that, when combined, create a material to leverage benefits of both of its constituents.)
For instance, wood (lignin/cellulose), bone (collagen/hydroxyapatite) and other well known artificially created materials such as fiberglass, carbon fiber or reinforced concrete qualify as composites.
When it comes to 3D printing, composites usually are a blend between either a plastic or nylon material reinforced with fibers of various compositions. Composite 3D printing allows for the manufacturing of lightweight yet robust parts thanks to the fibers mechanical properties.
Chopped Fiber or Continuous Fiber?
Chopped fibers, less than a millimeter long, are usually mixed with a nylon thermoplastic creating a filament material that can be printed using standard FDM (Fused Deposition Modeling) printing. The fibers increase the material’s stiffness without having any impact on its strength but may impact the overall part’s surface finish.
The true improvement of a material’s performances comes from the presence of continuous fibers running uninterrupted through the part thus distributing loads along the part. Needless to say that continuous fibers have a significant impact on a part’s strength and stiffness.
The most common fiber used is carbon fiber bearing the highest strength-to-weight ratio.
Continuous Filament Fabrication
Continuous Filament Fabrication (CFF) is Markforged’s flagship 3D printing process. The printers relying on such a process use two sequentially functioning extruders : one for the thermoplastic matrix and the other to lay the fiber. As the fiber is laid down, a thermoplastic layer is added around and above it in order to make it stick to the matrix.
With Markforged’s 3D printers, you have access to a variety of combinations between plastics and fibers. Each of these has a specific set of combined properties allowing the users to find the optimal combination for their particular needs. For instance, an Onyx FR / Carbon Fiber combination is perfect for particularly strong and flame repellent parts. Some combinations were even proven to be stronger yet lighter than some of their metal counterparts.
Not to say that composites will replace metals, each and every manufacturing process has its spot in the industry. Furthermore, composite and metal 3D printing can even work hand in hand to improve cost effectiveness and reliability in manufacturing.
Where to use Continuous Fibers 3D printing?
Each step of the design and manufacturing process can benefit from the use of highly resisting parts emanating from continuous fiber additive manufacturing.
Prototyping & Testing
3D printing allows shorter iteration cycles between initial prototypes. Continuous fibers allow for stronger and more functional parts which is rather helpful in the determination of their behaviour in a pre-production phase.
Tooling & Production
3D printing of composites materials can be used to design robust, complex and bespoke tools. The continuous fibers’ strength allows for these parts to be readily available and durable on the manufacturing line.
Assembly & Inspection
Supplement your assembly operations with strong 3D printed parts optimised for your production environment and processes. Build your inspection equipment without sacrificing stiffness nor durability.
Finished product and replacement parts
Implement 3D printing in the low volume production of functional parts used in finished products assemblies or to print on-demand replacement parts directly on your production line.
Composites 3D printing materials
Markforged uses high grade composites materials in order to print robust enough parts integrable in any step of the production process.
Markforged uses a base thermoplastic named Onyx, stronger than ABS- or Nylon-based materials used by other printers.
Onyx is a mix of Nylon and chopped carbon fibers thus creating a thermoplastic with outstanding properties: it is highly heat- and chemical-resistant and offers high quality finish. Used alone, it is 1.4 times stronger and stiffer than regular ABS. It can also be combined with continuous fiber material to improve some of its properties.
The Onyx FR composite shares similar properties with the standard Onyx whilst being a Blue Card UL94 V-0 certified material. It is ideal for applications requiring flame repellent, high strength and lightweight properties.
Nylon W is a tough material with smooth surface texture perfectly suitable for applications involving repeated skin contact or workholding when handling highly polished surfaces. It’s semi-glossy white surface finish also allows it to be painted or dyed.
Reinforcement Fiber Materials
Using the Continuous Filament Fabrication printing method to combine one of the matrix materials mentioned above with one of the fibers offered by markforged provides a whole set of different properties and advantages.
Fiberglass offers high strength for an affordable price. Eleven times more rigid than ABS, it is perfect for jigs, equipment, functional prototypes and certain finished products.
High Strength High Temperature (HSHT) Fiberglass is twice as strong as classic fiberglass. It has a much higher impact resistance and is able to withstand much higher temperatures whilst still offering high elasticity.
Carbon fiber has the highest strength-to-weight ratio of all the fibers offered by Markforged. It is sufficient enough to replace aluminium milled parts for half their weight.
Kevlar fibers are robust, lightweight, can handle heavy impacts and can be bent for than any other fiber. With a low density for high durability, it is the ideal material for applications involving movement or interactions with production parts.
Markforged’s composite printers line is split between desktop and industrial models. Most of them rely on Continuous Fiber Fabrication (CFF) as a printing method in order to produce particularly robust and versatile parts.
Markforged’s desktop series combines industrial quality with affordability integrated in an aluminium frame.
Markforged Mark Two
The MarkTwo industrial desktop 3D printer is small but able to produce high performance parts. On another level than the Onyx pro, this machine introduces additional support materials for an even broader versatility.
Tips to Be Successful with Continuous Filament Fabrication
The key to success in using continuous fibers relies on great understanding of 3D printing mechanics and in a good identification of the zones requiring fiber deposition. We will present you some good behaviours and practices to adopt in order to attain an optimal result.
How to identify where to position your fibers ?
- Identify the load case: Review your model and identify the areas subject to the higher loads.
- Define your part’s orientation: Make sure that your part is oriented so that the path of the main loads is parallel to the printing bed.
- Identify the support areas: determine the areas requiring the highest strength depending on the load case.
- Balance fiber walls: Make sure that your part is properly balanced to avoid warping effects.
- Confirm fiber path: Check that the fibers adjust and circulate along the part areas that require it.
- Shell: suitable for most load cases.
- Surface striping: used to increase the overall bending strength and to balance reinforcements.
- Ribs & fiber angles: orientates the fibers alongs a certain load path.