Steel parts from the printer

The entrance to the laboratory is at the back of the building. Inside are two computers, a few machines and an initially inconspicuous cabinet about three meters high. Small black glass elements are built into its doors. If you step closer and look through the glass, you immediately understand their function: these little windows are small protective goggles. Inside the cabinet, a fully automated welding head races over a panel, building up a structure layer by layer.

Christoph Dietenberger stands next to the machine. He completed his Master's degree in Product Development in Mechanical Engineering at RWU in 2023. And he built this machine. Or rather, he was the idea generator and driving force in the team that developed this metal 3D printer at RWU, project name: WIRED3D.

"Around ten years ago, the patents expired and the hype surrounding 3D printing began," says Christoph Dietenberger. He was working in this field at the time. "And I immediately thought, this has to be in metal and it has to be big." He started working in his garage at home. However, it was his Master's degree and his work at RWU that provided the right conditions for completing the machine. If you were to print out the prototypical Swabian inventor, he would probably not be so dissimilar to Christoph Dietenberger.

The machine prints two and a half kilos of steel per hour

The machine weighs around one ton. The floor in the new laboratory has been specially aligned so that nothing wobbles. Components up to a height of 1.5 meters can be printed. The base area can be up to 50 by 50 centimeters. The machine prints two and a half kilos of steel per hour. The welding head melts the supplied wire at 1,500 degrees and uses it to build up the digitally designed component, layer by layer in a previously defined pattern.

"We call these patterns print routines. They are very important for the subsequent material properties," explains Lukas Eichhorn, who is mainly responsible for the control and programming. When the machine was finished and the first parts came out, the engineers were initially faced with a problem. It makes a big difference whether the print head moves in a circle or zigzags. Each component requires a different strategy. In the meantime, the young team has printed many different strategies, documented all the process data and tested the results in the materials testing laboratory. "We now know pretty much exactly how we have to proceed in order to achieve the specified properties," says Christoph Dietenberger.

Jonas Leible is the third member of the team. He is also a graduate of RWU and developed the new print head in his final thesis, with welding torch, cooling, integrated extraction and the entire sensor system and camera monitoring. The machine uses a camera to detect the height of the layers and makes adjustments on its own. "But it wasn't just the three of us who built the machine. Support came from the entire faculty," says Christoph Dietenberger, "Lars Franke, for example, is a research assistant in the field of fluid mechanics, but he is also an absolute expert in industrial automation. Even in the initial phase of the project, he made sure that we used the right components for the control system."

The advantages are obvious

"What this team has created is fantastic," says the proud Dean of the Faculty of Mechanical Engineering, Professor Dr. Thomas Glogowski. And Professor Dr. Theresa Breckle, who is responsible for additive manufacturing in the faculty, adds: "We all benefit from this, especially our students." For example, the material tests are carried out in the laboratories on site and the resulting parts are characterized in terms of their properties.

Material properties are the point at which Christoph Dietenberger repeatedly has to answer critical questions. "There are centuries of tradition in casting and the material is precisely specified. What we do, on the other hand, is to a large extent pure empiricism; we test and gather experience," says the 36-year-old. Every time a process parameter is changed, the material properties change. How does the component lie on the carrier plate? What pattern is printed? At what speed? Different materials can also be combined. For example, the outer surface of a gear wheel can be made of a harder steel than the inside.

Even if printed steel is still often met with skepticism, there are a number of obvious advantages: there is significantly less waste than when a component is made from a block. Production is also tool-free, meaning that no molds need to be made for casting or the press.

Small quantities for prototypes and the procurement of spare parts

When the part comes out of the printer, however, it is not yet finished. The surface is still raw, consisting of an accumulation of weld seams. In the computer-controlled milling machine, the part is shaped to a hundredth of a millimeter. Finally, a metal band saw separates the shiny steel from the carrier plate on which the print was built up. Dietenberger, Eichhorn and Leible also built this saw themselves.

"We printed five components of the saw ourselves. Otherwise we would have had to have them cast," says Lukas Eichhorn. And Christoph Dietenberger adds: "We need around two days for smaller components, one for printing and one for post-processing. For larger parts, it can take up to a week. But we are currently waiting 30 weeks for a cast part."

The new machine is already being used in teaching. However, the three engineers are also looking for partners beyond the campus. Whether in prototype construction or in the procurement of spare parts, the three are certain that they are more flexible, faster and - for small quantities - also cheaper than conventional processes. "We are looking for partners that we can help with our metal 3D printing," says Christoph Dietenberger. "We gain experience with every part we produce and can therefore make more precise statements about its properties."

When you leave the small laboratory again through the back door, you have a very unspectacular view of pastures and forest. But you leave with the impression that something extraordinary is happening behind this door, that a handful of inventors have come together who will not rest as long as there is still an open question. Or, as Thomas Glogowski says: "Once again, you can see that good people find each other."

Text/photo: Christoph Oldenkotte
Video: Alec Weber