How metallic 3D printing could transform manufacturing

“Beam me up, Scotty!” Back in the 1960s, in the vast expanses of Star Trek, matter was already being “beamed” across the universe to and from the starship Enterprise and reassembled into its original state on reaching its destination. Even the protagonists of this space opera had themselves seemingly magically teleported from one place to another. Some viewers believe that the main reason why the producers of Star Trek invented "beaming" as a method of space travel is that over 50 years ago it would supposedly have been too expensive and troublesome to film scenes in which the Enterprise landed or took off from other planets.

But while scientists continue to debate whether such a teleportation system could ever be created, technologies already exist that might make a layperson think of Star Trek’s beams. One of these technologies is additive manufacturing, which long ago stopped being science fiction or a vision of the far future.

At Daimler, the future of 3D printing has a name: NextGenAM

This process transforms digital data into real-life, three-dimensional shapes. In a 3D printer, metal powder is applied one layer over the other, melted by a laser, and hardened within the blink of an eye. This technology is used to produce components for the aerospace industry and prototypes for the automotive sector. However, there are examples from other sectors as well. Among other things, it is used to manufacture stainless steel and ceramic prostheses for the medical technology sector as well as jewellery made of valuable materials like platinum, silver and gold.

None of this is really brand new, either. This type of 3D printing, which is referred to as selective laser melting (SLM), has already been used at an industrial level for over ten years. Nevertheless, it would be a whole new challenge to develop this method to maturity for the automated production of large component quantities in car manufacturing.

And this is precisely what Daimler is doing with the NextGenAM project. The project’s name stands for Next Generation of Additive Manufacturing, which Daimler and its partners, Premium AEROTEC  and EOS , have been developing since 2017. “We started with a blank sheet,” explains Michael Lahres, Head of Additive Processes at Daimler, as he describes the starting point of the pilot project. This project was not so much about developing brand new technologies but more about intelligently interconnecting the expertise of the three partners. The goal was to establish a digital production line with the available components (i.e. the machine equipment and the material), which would be able to produce aluminum parts for the automotive and aviation industries in a more profitable way than before.

The project has now been successfully completed. It reduced the 3D printing costs for a car shock absorber bracket as a sample part by around 50 percent while retaining the same quality. At the same time, the production process at Premium AEROTEC passed the audit in accordance with the stringent industry standards of the VDA 6.3, which was a prerequisite for its use for series production.

Growth by a hair’s width

“3D printing is, so to speak, a new forming process, which, alongside conventional processes like casting or sintering, offers us new ways to generate materials in their original state. Especially by using metals like aluminum or steel. This enables us to produce spare and serial parts without tools,” explains Michael Lahres. The entire technical fascination of additive manufacturing  becomes clear when he goes into detail. A prerequisite for additive manufacturing is a digital model of the component to be printed, which is then broken down into layers — each between 30 and 80 micrometers (µm) thick. By way of comparison, an average European’s hair measures 40 to 60 µm. This means that each new layer of powder that is applied, is roughly the thickness of a hair. It is precisely melted to the surface of the component by the laser and thus fixed to the layer below it. In this way, the component steadily grows in its powder bath. The strength, properties, and material quality of the component can be controlled through the use of different grain sizes in the powder, ranging from 5 to 60 µm. And through the mixing ratio and the distribution of the different grain sizes in the powder.

“If the metal alloy is comparable, the material properties of 3D printing generally exceed those of a cast part. Thanks to the heat input of the laser, the material hardens more consistently,” says Lahres. However, such a part would not yet be ready for use. The addition of the layers with radical heating and rapid cooling creates “frozen, metastable microstructure states in the material,” to use the technical terms. Lahres explains: “To prevent the component from becoming too brittle, we need to apply a subsequent heat treatment.” This makes the structure of the material more uniform and tailored to the requirements profile of its intended purpose.

Lahres describes this broad field as the company’s most fundamental knowledge. “Through our deep, fundamental understanding of the materials, we can perfectly process the component to get the best result for the specific application.” This shows that the future is not just determined by digitisation. Without the fundamental knowledge of material science that the experts at Daimler possess, NextGenAM would not have succeeded. But neither would it have done so without digitisation.

Fully automated production

“The secret is that we merge our competencies,” says Oliver Neufang from Corporate Research at Daimler. Neufang is an engineer on the Production Processes & Factory Integration team and with this expertise he played a leading role in the NextGenAM project. “During the definition of the new process, we had the chance to anchor the principle of Industry 4.0 firmly in the process. We first established this in the printing scene. As soon as the component has been converted into data, the system functions autonomously.”

All the process steps of the scalable production chain are interconnected and controlled via a central control station: preparing the data, supplying the powder, the AM laser process, shaking off unmolten powder, the heat treatment, quality assurance, and cutting the component off the carrier plate. Robots and a driverless transport system ensure the smooth progress of the components along the entire production line, which can produce an entire series or even a completely different component in the very next cycle. “If a faulty component is identified by the fully automated quality assurance at the end of production, the system can take the necessary measures to prevent further errors in subsequent parts. Thanks to the continuous 3D data chain at the beginning of production. That is Industry 4.0!”

With a shock absorber bracket for a car engine as the reference object, NextGenAM proved the technical and, above all, economic feasibility of 3D printing. This sample part had already been optimized for the new production method in terms of design and material more than three years ago. In the course of the project, it was employed many times over to assess the progress of the technological development and the costs. As stated previously, costs were, in the end, reduced by around 50 percent, while maintaining the same high quality. The properties of the classic aluminum alloy (AlSi10Mg) were also continuously improved, which enabled significant increases in the material strength value and surface quality. Like conventional cast parts, the blanks for 3D printing are transferred to post-processing when necessary. For example in order to optimize the surfaces for the respective application or to cut threads and bore holes.

3D printing creates parts on demand

The NextGenAM project laid the foundations for the future series production of printed components for Daimler. In the future, in addition to small series and parts for pre-development, it will also be possible to produce larger quantities via 3D printing. According to Oliver Neufang, an important element is that the knowledge was transferred from Corporate Research to the development project. “We incorporate many disciplines and are in constant exchange with our colleagues,” he says. “They benefit from our know-how in additive manufacturing: What is possible — and what is not? It is important to evaluate the influence of the individual components. For example, with this knowledge, an engineer can incorporate cavities in the design that would not be possible in a cast part. This would reduce the weight, for instance.” This means suitable components can be developed specifically with the possibilities of 3D printing in mind: with new, integrated functionalities, bionic shapes, and optimized weight — the latter is a particularly interesting possibility for electric vehicles.

3D printing is especially suitable for the spare parts segment. For one thing, in the event of a tool defect, seldom-required parts can often be reproduced much more inexpensively than if a new mold had to be manufactured first. To do so, the data for the tool simply needs to be prepared in 3D. However, Daimler has set its sights on even greater advantages in its vision of digital stock: the centralized provision of digital production data for the decentralized 3D printing of spare parts. This would allow parts to be printed on demand for a small stock, instead of storing them in larger quantities at high cost.

Open to technological progress

All of this shows that NextGenAM is a milestone on the path to digital production. For Michael Lahres and Oliver Neufang it’s especially important that the process isn’t chained to the current system status. But open to technological progress with regard to the components of the 3D printing system, greater assembly sizes, and more advanced materials. However, the two experts don’t claim that the technology might be a solution for every situation. On the contrary, “there are good technological reasons why components are cast, pressed, forged, shaped or molded with the established production methods,” says Lahres. “3D printing will not replace all other processes, but complement them where it makes sense. We want to identify all the components that could be produced more efficiently and economically by means of printing.”

Are printed cars on the way?

One question remains: Will entire cars be 3D printed one day? A lot could be done in theory, but the two experts don’t see it happening in practice. A vehicle is too complex. So even in the future, there remains room for some science fiction.