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How robust are 3D printed parts made of plastics and metals?

Probably the most persistent prejudice against additive manufacturing is that 3D printing produces precise, but not very robust and hardly resilient components.

Conventional plastic components produced by machining or injection molding are much more reliable, can withstand higher forces and, above all, are much more durable than components from the 3D printer. But what is really true about these prejudices? Can the stability in 3D printing really not keep up with conventional processes - despite all the further developments in high-performance plastics, fiber-reinforced materials or the absolute design freedom in additive manufacturing? We took a closer look at the common prejudices.

Stability is always a question of the material used

SLS PA12 Bauteile direkt aus dem Druc

As early as eight years ago, a dissertation from the TU Darmstadt (external link, dissertation, pdf document) addressed the topic of "3D printing processes for compact and mechanically stable molded parts". As part of the highly interesting doctoral thesis, monomer inks and powders were scrutinized in terms of shape fidelity, volume balance and shrinkage behavior. The bottom line of the doctoral thesis is that in 3D printing, the stability of printed parts is directly dependent on the materials and printing process used.

Several years have passed since the doctoral thesis was written, during which the high-performance plastics used in particular have undergone a significant upgrade in terms of robustness and stability. The main drivers of innovation here are the aerospace, aviation and automotive industries. These sectors demand particularly stable components made of robust materials. Polyamide, carbon reinforced filaments or inserted continuous fibers make it possible to develop lightweight components that can absorb even the strongest forces.

From powder to highly stable components

In the field of additive manufacturing, the two processes of selective laser sintering (SLS) and selective laser melting (SLM) are primarily used for the production of robust components. Both processes work with the same material state: powder. While laser sintering generally uses polyamides, laser melting is suitable for 3D printing metals. The powdered starting materials are applied to the 3D printer's working platform by means of a roller or squeegee and heated point by point by a laser according to the desired geometry.

Once the desired shape has been achieved, the working platform is lowered by around 100 micrometers and the process is repeated. Layer by layer, the workpiece is thus built up from the bottom to the top of the powder bed. On the one hand, the layer-by-layer buildup with extremely thin layers achieves very high precision, and on the other hand, material densities of 99% are possible without any problems. This means that the density of the printed parts is almost identical to the density of other materials from conventional production. Or to put it another way: with the right printing process, 3D-printed parts are just as stable as conventionally manufactured components in the same material.

Can it be a little more robust and stable?

In conventional manufacturing, every material used has very specific properties. Tensile and breaking elongation, resistance to plastic deformation or separation, or the hardness of a material are predefined and can only be extended to the natural limits. The behavior of a sheet of aluminum or steel can be defined or controlled by the alloying constituents during production and the actual processing of the material. Properties can be further optimized by bonding or mechanical connections with other materials.

What is missing, however, are creative degrees of freedom in the design; the restrictions regarding the accessibility of tools or the demoldability from injection molds remain. This is precisely where the advantages of additive manufacturing come into play. On the one hand, laser melting makes it possible to print metallic workpieces whose density is up to 99.9% that of rolled or forged material. In addition, different materials can be combined in the 3D printer. By reinforcing with carbon fibers directly during production or inserting continuous fibers, plastics can be made even more stable, robust and, above all, precisely adapted to the respective application. And all this with absolute design freedom, which allows, for example, load-optimized internal rib structures, internal cavities, or flow channels.

 

Generative design: stability based on nature's example

Evolution is enormously good at implementing flow rates, thermal efficiency or vibration reduction - even better than human technology is capable of. With ever-increasing computing power and advances in artificial intelligence, it is now possible to come close to nature's models in the field of additive manufacturing. 3D printing allows the design of previously traditionally manufactured components to be adapted in such a way that not only can the components be produced much more efficiently and with much less waste, but performance, stability and robustness are also significantly increased.

Automated calculations in the CAD environment thus create near-natural, almost organic-looking shapes - a copy of nature, which is known to "engineer" to perfection. Generative design allows the production of parts that are once again significantly more stable than comparable workpieces produced using conventional 3D printing, while keeping weight to a maximum.

 

3D printing design with lattice structures

Lattice structures, for example, currently offer an excellent opportunity to completely redesign components that were previously manufactured in solid material. Less weight, lower costs and yet maximum stability: lightweight structural design is undoubtedly an area that offers many and completely new design possibilities thanks to modern additive manufacturing processes. Read more about it in our blog: Lattice Structures

 

Conclusion: prejudice debunked!

Parts from the 3D printer look good, but cannot compete with conventionally manufactured components in terms of stability and robustness: For years, this prejudice has run through the conversations that arise around the topic of 3D printing processes. In the early years of additive manufacturing, this prejudice may have been true - state-of-the-art 3D printing processes, however, are throwing the prejudice where it belongs: on the discard pile of outdated views.

In particular, 3D printed parts from the powder bed are completely comparable to conventional components in terms of both stability and robustness. Moreover, through the clever combination of materials and printing processes, all components can be adapted quite precisely to their intended use. With constantly expanding computing power and the use of artificial intelligence, generative design is also made possible - which is based directly on nature's perfect "constructions" and thus maximizes the stability-to-weight ratio.

Do you have any questions about the potential applications of additive manufacturing in combination with industrial plastics or metals, or would you like to discuss a specific project with us? Then the best thing to do is to get in touch with us right away!

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Markus Grimm
Chief Virtual Printfactory

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