Additive Manufacturing is gradually gaining inertia throughout the different branches of industry. However, one of the mains obstacles is the endurance and performance the parts deliver – the need to strengthen 3D printed parts is paramount. Since the most commonly used material in 3D printers is a form of polymer or plastic, the limitations in the type of parts that can be manufactured through the process, and their durability, are there for all to see. Thankfully, there have been a number of recent developments and future possibilities when it comes to manufacturing stronger parts – able to rival and compete with steel and composite ones. The ability to strengthen 3D printed parts would add a whole new layer of value to the 3D printing process.
New processes in Additive Manufacturing:
The first efforts to strengthen 3D printed parts were focused on simply using high strength material, and therefore adapting the 3D printers to the requirements of such deposition. SLS (there are other processes as well) is one method used in additive manufacturing to provide high strength parts and build components with very solicited working conditions. These processes are commercially available throughout different companies and are known as SLM (Selective Laser Melting), EBM (Electron Beam Melting) and DMLS (Direct Metal Laser Sintering). They rely on a powder deposition method to spread powder layers and construct layers that are either bound or melted together.
These processes are however very expensive and demanding in terms of resources and energy consumption. Moreover, their use is still restricted to a few components given the complexity of inspecting the parts and the expensive if not unavailable analysis protocols for them (required for certification and testing purposes).
Since the composites’ surge, “everything is better with a handful of fibres thrown in” became a trend for some time. Therefore, throwing in short carbon fibres in the resin of the 3D printer was an understandable development. After all, the resin will act as a matrix and the fibres will provide the mechanical properties desired in a strong part. Needless to say, many learned to their expenses that no, throwing a handful of long, and even worse, short carbon/glass fibres in the cauldron won’t make your parts better. If anything, they can prove disastrous due to the negligence of the anisotropy of these components and the unawareness of the amount of calculations and study they require before including them in a composite and structuring them in a specific use. Research into the micromechanics of the layers and the fluid dynamics of the reinforced resin is ongoing to check the predictability of the fibres’ orientation and their properties within the FDM process.
There is a more informed way to include fibres in a 3D printed part: either through some brands of 3D printers that allow the user to choose the fibre routing and hence orientation while building the layers, or through manual composition by filling a 3D printed shell of the desired part. Both of these methods are used extensively by hobbyists. While these methods can give satisfactory results, they require extensive post-treatment, and aren’t used on large scale parts, let alone ones for industrial purposes.
Adaption of parts:
On occasion a complete revision of the parts’ model will be required when it is submitted to a slicer. From reconsidering the shapes to scaling the geometry and modifying certain features, there are several tricks to 3D printing. To ensure a part is strong on its own, it will either be assembled using supports, or treated with heat and a special coating. These processes are the most common currently used and imply there is still work required to encourage widespread use of AM.
Even though research is ongoing through the viscoelastic aspect of mould flow, short fibre orientation and the degree of control we can have on it, there have been some promising results. Very soon we may be able to automatize the whole process and come to a situation where dumping a handful of short carbon fibres in the machine will result in adequate orientation within a 3D printed part. While there is much work still to do there is no doubt that the process required to strengthen 3D printed parts is moving in the right direction.