SIEMENS

At first glance, the machine looks like an outsized refrigerator with an observation window. But inside, it’s anything but cold. On the other side of the window is a mold bed. Inside it is a fine, smoothly distributed layer of gray powder from which glittering motes shoot out as if from a sparkler. A hexagonal pattern of light moves across the powder’s surface. After a while, you can start to make out a regular structure, like something being written into the gray powder by an invisible pen.

“Our ‘pen’ is a laser beam; it is guided straight downward onto the bed of powder by a deflection mirror in the upper part of the process chamber,” says Dr. Olaf Rehme of Siemens Corporate Technology (CT) in Berlin. “At the point where the laser hits the stainless steel powder, the temperature rises to the powder’s melting point, which is higher than 1,500 degrees Celsius. That’s when the particles fuse together.”
The deflection of the laser – its writing movement, in other words – is controlled by a computer, which holds the electronic blueprint for a complex stainless steel workpiece. After the laser has fully traced the regular pattern, the powder platform descends by an almost imperceptible amount. A slider mechanism spreads a new, approximately 50-micrometer-thick layer of powder, and the blazing pen goes into action once more. “This is how we create three-dimensional structures made of stainless steel, layer by layer,” says Rehme.

The machine is located in one of the many laboratories in the Siemensstadt district of Berlin. Here, Siemens is conducting long-term studies for customers and partners in order to determine which of their products and product components can be manufactured by means of laser melting. “The term ‘3D printing’ is often used as a synonym for all processes of this sort,” says Dr. Ursus Krüger, head of the research group. “But in professional circles, the term ‘additive manufacturing’ is usually used to refer to these techniques as a class. These processes don’t have much in common with ‘3D printers’ anymore.”

The first 3D printers were developed as early as the 1980s. They mostly used plastics that harden quickly. These were sprayed on layer for layer and eventually resulted in a three-dimensional object. Machines of this type were especially useful for rapid prototyping, a process designed to create inexpensive prototypes and design studies in short order. “Today, plastic printers of this sort are available for home use at affordable prices, starting at about 1,000 euros,” says Krüger. “Such machines are popular among model-makers and amateur craftsmen.”
And even 30 years after their invention, 3D printers are still making headlines. The media routinely carry reports of the use of such printers, often for demonstration purposes or as part of a PR campaign. In 2011, for example, British engineers of the EADS Group “printed” a complete bicycle out of nylon powder. A small number of individual parts from the printer were assembled and then equipped with a chain and tires – the “print bike” is stable and light, but it’s a bit wobbly to ride.

Suitable for Ceramics. But apart from spectacular examples, it’s clear that 3D printing technology has long since outgrown its prototyping roots. Today, laser-based processes such as laser melting can process not only plastics but also ceramics and many metals, including stainless steel, aluminum, and titanium, for instance. “That means the technology has reached the point where it’s useful for industrial applications,” says Krüger. But you can’t call this printing any longer, because almost all of these processes harden or fuse a liquid or powdery matrix at specific points to produce an object.

Some companies have already specialized in the production of hip joints, hearing aids, spare parts for cars, or dentures. For example, BEGO Medical GmbH in Bremen, Germany, produces metal frameworks for dental crowns and bridges by means of additive manufacturing. Components are already being produced this way for Formula One racing and in the aviation industry, and German companies such as EOS and Concept Laser are leaders in the world of additive manufacturing machines.
“But these companies have plenty of competition,” says Krüger. “In the summer of 2012, for example, U.S President Barack Obama announced the formation of an American research institute that will concentrate on developing innovations in the field of additive manufacturing.”

The participants in the planned National Network for Manufacturing Innovation – NNMI – will include government agencies like NASA, the National Science Foundation, and the Department of Defense, as well as universities and companies such as Boeing and IBM. The primary objective is to make up ground with respect to competitors – those of today from Europe, and those of tomorrow from China, Japan and Korea.

Are such investments worthwhile? Is there really a revolutionary future in the offing? Will there be a time when any small company will be able to manufacture any conceivable part by itself? “It’s still too early to tell,” says Krüger. “But the advantages are already obvious. With additive manufacturing, you can make highly complex workpieces with concave parts and intricate bracings inside, the sorts of parts that would otherwise have to be handcrafted or made in multiple individual parts; but now they can be produced in a single, computer-controlled step.”

On the other hand, the weaknesses of technologies such as laser melting are also evident. “Workpieces are created from a bed of very fine particles, resulting in a characteristic structure and surface. In mechanical engineering, especially, where certain parts have to withstand extreme physical stresses, conventionally manufactured forgings still have an advantage with regard to sturdiness,” says Krüger. Furthermore, producing a part by means of laser melting is a very protracted process – more than a hundred production hours are sometimes needed for large workpieces. “But the overall throughput time of a workpiece can be greatly reduced with laser melting,” adds Krüger. “Because in contrast to conventionally produced parts, which often have to be reworked several times, these workpieces are made in the process chamber of the laser melting machine.” Surface quality is the only thing that might have to be improved, meaning, for instance, a final polishing step.

“The strength of the technology is that it can be used to produce complex individual pieces or parts that are needed in small quantities,” says Krüger. “A classic example from our own product development is a new duct system, known as a ‘transition duct’, for gas flows in gas turbines,” says Martin Schäfer, who has been working with this technology at Siemens CT since the late 1990s. “This curved, thin-walled part has very small channels, and it’s extremely difficult to make it with conventional technologies such as casting and milling. But with additive manufacturing, these metal parts can be produced right from a computer in just a few days, instead of weeks,” says Schäfer.

This example illustrates how additive manufacturing can be used to reduce production times and easily implement new design concepts. “The parts melted here have passed all the tests, and now what we have to do is get the technology ready for the transition to production,” explains Schäfer.

To that end, various projects are underway with several Siemens groups. There are also external collaborations such as the DMRC (Direct Manufacturing Research Center) in Paderborn, Germany, in which CT is studying how processes and materials can be improved, on behalf of Siemens Energy. Boeing and key companies at the vanguard of this technology, including EOS, SLM Solutions, and Stratasys are also participating in DMRC activities. “Engineers have to completely revise their thinking,” says Krüger. “With additive manufacturing, all conceivable shapes can, in principle, be manufactured in just one step. So in the future, the shapes that are possible will be limited only by whether the design created on the computer is physically viable; but not by the characteristics of milling or stamping machines.”

Larger, Faster Machines. How far might additive manufacturing take us? “There are limits imposed by physics with regard to the lasers and, above all, the required cooling times. But despite that, we’re working on going as far as this technology can take us,” says Krüger. “The machines will get larger, and they’ll be able to use multiple lasers at once. That will speed up the whole process considerably, making it more economical to produce very large parts. There are already examples of this trend toward larger machines. At the Euromold trade show, which took place in late November 2012 in Frankfurt am Main, for instance, some of the machines being shown had build chambers capable of handling edge lengths of up to 600 by 400 millimeters.”

In Krüger’s view, the best opportunities for putting additive manufacturing into action are in the service field. For large industrial plants, for instance, each minute of downtime costs a lot of money. So if something breaks down, spare parts have to be shipped to the site as quickly as possible.

“But suppose, instead, that one of our gas turbine customers could simply order a spare part from the nearest Siemens service outlet,” says Krüger. “The local service provider would just have to call up the part’s data package and manufacture the part right there with its own laser system. There would be no transportation costs for spare parts from distant locations. Downtime would be minimized. There would be no warehousing of spare parts, because only the digital blueprints would have to be saved. When you add it all up, you can see that Siemens could supply customers around the world with replacement parts in a cost-effective and environmentally-friendly way through a network of local service points.”

Spare parts of any size “on demand” and available worldwide without having to set up dedicated production lines – just a laser melting machine, operated by one or two technicians. Regular service updates with new blueprints for any number of parts, via e-mail from headquarters. That sounds like an idealized vision of the distant future. But as soon as the machines have reached the required size and speed, one is practically forced to imagine applications like this. And given the global efforts underway – whether at companies such as Siemens and Boeing, equipment makers such as EOS, or emerging research networks such as the NNMI – there is reason to expect rapid development.

Despite all the euphoria, however, new challenges are looming too. “In the coming decades, data protection will take on major importance in the field of additive manufacturing,” says Krüger. “The data owned by the company – electronic blueprints – have to be protected from people who would make pirate copies.” Because if any conceivable part can be manufactured by any sufficiently advanced laser melting machine, a professional counterfeiter needs only one thing: the data.