“Why aren't we doing that?!”

“Why aren't we doing that?!”
Marginal Column
Prof. Dr.-Ing. Andreas Gebhardt

Prof. Dr.-Ing. Andreas Gebhardt is Dean of the Faculty of Mechanical Engineering and Mechatronics at the Aachen University of Applied Sciences. From 1991 to 1997, he was Managing Director of the Laser Processing and Consulting Center in North Rhine-Westphalia and the Center for Prototyping, which has been dealing with 3-D printing as a service since 1992. In 2000, he was appointed professor of high-performance methods of manufacturing technology and rapid prototyping. He also teaches at the City College of the City University of New York and is a professor at the Technical University in Pretoria, TUT. He is the author of the standard work “Additive Manufacturing” and editor of the RTeJournal, an open-access online journal for rapid technology.

Copyright Photo: FH Aachen


July 2016


Prof. Dr.-Ing. Andreas Gebhardt has been dealing with additive manufacturing technologies since the 1990s. In this interview he talks about the potential, risks and development of the procedures. He expects drastic changes in industrial production and calls for greater consistency in thought and in training.

Additive manufacturing and 3-D printing are often used synonymously. Where do the differences lie?

The history of additive manufacturing dates back to the mid-1980s. At that time, we called the process "rapid prototyping". Not because the procedure itself was particularly fast - it's still not fast today - but because additional tools were not needed to produce a prototype, making it significantly faster. This name, although precise, was cumbersome and in need of an explanation. Therefore, as with any new technology, a variety of terms has emerged. "Rapid prototyping" was followed by "rapid manufacturing", followed by "additive manufacturing". When in the year 2000 smaller machines costing anywhere from 500 to 2,500 euros began to be used in the private sector, the hitherto scorned term "3-D printing" started becoming more popular.

So the terms are process-independent, right?

When the term "3-D printing" was born into the world, it referred more to the small, privately-used devices. In the meanwhile, the term is also used for expensive, industrial machines. Many people even leave out the "3-D" nowadays and speak only of a "printer" or a special "metal printer". In this respect, procedure-related boundaries no longer exist.

Many different materials can be used. Which challenges does this pose?

Today, components can be "printed" from all existing material classes: Plastics, metals and ceramics. The material itself is still the key to success – and will remain so. One reason for this is that, in contrast to conventional manufacturing using semi-finished parts, the material properties - form and quality - only first arise during the production process in 3-D printing. Powder, for instance, is melted with a laser and produces a solid layer after cooling off. Here, both the type and size of the powder particles play a part. And also the molten pool created by the entry of the laser and its dynamics have an influence on the result. The interaction between the generating element, in this case the laser beam, and the powder creates different material properties locally. Therefore, it is a challenge to get the component that one actually wants.

What possibilities does the future hold with regards to materials?

Overall, the range of materials in each class of material is much smaller than the classic range. In the M-base plastics database we found a total of nearly 50,000 plastics, of which just 50 are available for use in additive manufacturing. The range definitely needs to be extended. The requested quantities, however, still do not justify this at the present time. They are still too small.

Worldwide, there are currently about 50,000 small plastic machines in operation. We believe that this figure is going to double in 2016. With the expansion of this technology in the industrial and commercial sector, the volume of materials needed is growing, too. Metal machines, for example, are going to get significantly larger. The physical size was once 125 x 125 x 125 mm. Today, we are at 700 x 400 x 400 mm. This volume has to be filled with powder. More and more manufacturers are going to view this as a new market and are going to focus on developing materials. The diversity and competition are going to grow, prices are going to fall and quantities are going to increase.

How does development look in the field of material properties?

In terms of plastic, digital materials are an exciting development. Imagine a conventional color printer: When you print an image with it, the various colors from the four cartridges are digitally mixed. You can do exactly the same thing with 3-D printing, except that you can also influence other properties, for example the flexibility. This allows you to print a component that carries different properties. It can be harder on one side, for example, and softer on the other. So to put it in perspective, a complete windshield wiper could be produced in one piece in a single printing process. I could also imagine printing the corresponding reservoir in one piece: a lid with integrated seal, a transparent reservoir with level indicator and label and integrated mechatronic parts. For me, this is the characteristic that distinguishes 3-D printing from all other manufacturing processes: It has the potential to adapt components geometrically and in terms of their physical characteristics locally using digital controls.

You already mentioned the issue of speed. How can it be increased?

There's a whole assortment of concepts. Especially when it comes to laser-based systems. Things are moving towards the use of multiple lasers that share the work. This is, of course, very expensive in terms of the joint management of the lasers. In addition, there are other approaches, such as customized coating thicknesses. They allow some layers to be thicker and, thus, the component to be manufactured faster. Only in places where finer details are needed are thin layers applied. This depends on the particular geometry of the component.

What is the challenge in addition to the speed?

In terms of the machines and materials, we are currently trying to get a firm grip on the issue of reproducibility. As long as we talk about prototypes, it is usually accepted when processes and the properties of the components are not always exactly the same. But when we begin producing and selling, the component must have exactly the warranted characteristics. Process control plays a very important role here.

What are the limitations to constructive and creative freedom?

At first people said: "We can print anything." And indeed we are free from a number of limitations, but we can't outsmart physics. You always need to look at the geometry in terms of the printing process. What many people have not yet understood is that design and manufacturing have merged much closer together. When I construct something on the computer, then it's manufactured exactly that way. The goal of the construction must be capturing the benefits of 3-D printing in design rules. A fine example is the development of the first additive manufactured metal component in the civil aviation sector, which was a cabin. At the beginning, the construction was still very classic. Then construction followed along the load line, leaving familiar formulas behind. The result is a novel bionic-geometric solution. This thought must be rigorously pursued. Otherwise we will just be using 3-D printing to do what we could also do without it in the future.

So new thinking is required for designers.

Yes, the limits lie partly in the lack of imagination, but also in training.

You are sitting there at the source. How is training helping to enable this new way of thinking?

In 2000, I was appointed Chair of the first department dealing exclusively with this topic. In the meantime, there is now not a single college in the world where 3-D printing doesn't appear somewhere in the curriculum. But commercial training is still in its infancy, and not only in Germany. A three-day training course is not enough since it's not just about how to use it.

We're currently in the process of designing an extra-occupational training course for technicians, which will start at the end of the year. And we're driving today to companies in a double decker bus with eleven workstations equipped with 3-D printers. So commercial employees most of all can get a better picture of the new technology.

In addition, a new teaching method is needed. We currently teach revolutionary 3-D technology with the 2-D education techniques of yesteryear. This applies in particular to extra-occupational or even vocationally-integrated approaches. A lot is happening, but a lot more still needs to be done.

How will additive manufacturing change industrial manufacturing?

We are going to exploit the possibilities of individualizing products. You see that with products already being manufactured today, for example dental prostheses and hearing aid shells – no two products are alike. However, more items also means that the organization needs to adapt. At all times, precisely the right part needs to be identified, produced and delivered. This will not work without the integration of IT into the manufacturing process. The development, which is behind Industry 4.0, already reflects this.

In addition, the importance of the assembly process will decrease. I can already integrate many components, that so far were mounted in subsequent steps, into the device – and even achieve the perfect surface quality. When it comes to spare parts, the jam-packed lattice boxes are going to vanish. Variety is going to increase thanks to product-specific construction. That's because I can revise the design in economically reasonable and yet short intervals with this process. This is not possible at the moment due to the expensive manufacturing tools. This development will require more flexibility and better training of the people involved in the production.

How fast will this procedure assert itself?

There will be upheavals in various industries. The more individual the product has to be, the stronger an entry this technology is going to make in the realm of industrial manufacturing. Today, for example, hearing aids are without exception made by printing. In 2000, there were already none – within two years, the proportion of the printed hearing aid shells grew from ten to nearly 100 percent. Today we call this "disruptive". At that moment in which it is clear that a new technology will bring economic benefits it will experience a breakthrough. Within the next five years, I foresee many dramatic changes.

In which industries will these changes be seen most clearly?

That's hard to say. But I think that the fastest and most dramatic changes will be seen with regard to metal. We already see quite a number of 3-D printing applications for metals that, until very recently, we would not have thought possible. And then the pull-effect kicks in. If a manufacturer successfully brings an application to the market, the next one immediately asks: "Why aren't we doing that?!" This trend then gains a firm foothold. An aircraft manufacturer has just opened a new production site for printed metal parts.

What risks do you see in the industrial sector?

Liability is an important keyword. Because we are going to have the same product liability as before – but now for individual parts. In addition, the copyright question takes on a new dimension: Previously, if music or movies were downloaded illegally, it was annoying, but they weren't altered. If you acquire 3-D printing data, you can change the component and put it into circulation. Then if an accident happens with this component, the originator must demonstrate that the component was not his.

How is additive manufacturing developing internationally?

The whole world is involved with the issue of 3-D printing. For example, consider the new business model behind 3DHubs: On this Internet platform, private printing service providers are networked. Whoever wants to have something printed looks for a printer in their vicinity, negotiates a price and sends their file there. Currently around 30,000 printers are networked worldwide – and in really every corner of the world. All universities are also dealing with this issue. Internationalization also means internationalization with regard to knowledge.

Can that be demonstrated using examples?

In 2005, plastic printing machines were most common in the United States, Britain and Germany – in China there was next to nothing. All this has changed completely. When it comes to metal printers, there were five manufacturers in the world, including four in Germany. Since then, the United States, Britain and China have become very active. When it comes to the USA, unlike the rest of the world, there's a real possibility to initiate projects very pragmatically.