3D printing isn’t new to Deutsche Bahn. The German railway company started indeed to use a 3D printer in 2015. Since then, it has printed more than 7,000 spare parts. DB is the first operator to have carried out 3D printing certification, granted by TÜV SÜD, one of the main certification bodies in this area.
With 3D printing, the DB can produce metal spare parts within a short time, thus drastically reducing delivery times. « By this way we can ensure a better supply of spare parts and make the vehicles available to our passengers again faster,» says Stefanie Brickwede, project manager for 3D printing at Deutsche Bahn. « In particular, it is about parts that are associated with long delivery times or that would no longer be available. »
Until recently, 3D printing seemed to involve only light plastic parts. The evolution of 3D printing technologies has made it possible to develop a whole range of high performance plastic filaments which have mechanical characteristics similar to metals. There are several types of high performance materials that can be distinguished by family, such as that of polyaryletherketones (PAEK) or even polyetherimides (PEI).
But things are changing quickly. Metal 3D printing is now available. For several years, the technology of Metal binder jetting has experienced significant development. The process is now used by the biggest players in metal additive manufacturing. While metal 3D printing today mainly uses laser fusion techniques on a powder bed or electron beam fusion, many other technologies are emerging, explains the french webzine Technique de l’ingénieur.
However, 3D printing should not be confused with machining, as so sophisticated it may be. They key difference is that 3D printing is a form of additive manufacturing, whilst machining is subtractive. This means machining starts with a block of material (called a blank), and cuts away material to create the finished part. That produces many wastes. Reducing waste fits perfectly into a global ecological policy and 3D printing can meet these challenges. But of course, behind this there are many financial advantages.
Today, the global metal additive manufacturing market exceeds all growth forecasts. This market offers a great interest to the railways, which are among the largest consumers of metal in the industrial world.
Shorter delivery times, less production waste, there are many advantages. The delivery and waiting time for heavy special parts for vehicle maintenance could take previously taken up to 24 months. The new printing process has significantly reduced this time. « With the breakthrough in metal printing, we can now gradually ensure a faster supply of spare parts and our trains are quickly on the track again, » says Sabina Jeschke, DB board member for digitization and technology. « The aim is to have around 10,000 different spare parts available on 3D printing by 2021 ».
The process not only saves time, but also raw materials, since spare parts no longer have to be stored in large quantities, but could be manufactured if necessary. Deutsche Bahn states that this minimizes production waste, reduces inventory and eliminates numerous transports. Additive manufacturing thus makes a contribution to environmental protection.
Another motivation is that after 20 years, the spare parts are simply no longer produced. Some devices are also obsolete, like everything related to electricity. Over time, standard wear-and-tear and brittleness gradually weaken the injection-molded parts, meaning that they need to be replaced every 10 to 15 years. Rail vehicles are designed to have a service life of over 25 years, but it is not uncommon for a train to remain in service for 40 to 50 years, or even longer in exceptional cases. 3D printing allows you to redo parts you no longer find.
The 3D printing process is used to create three-dimensional objects by applying and solidifying the material in thin layers. There are two common processes:
- 3D printing by depositing molten material under the name of Fused Deposition Modeling (FDM). It is a process that uses a continuous filament of a thermoplastic material. The print head is moved under computer control to define the printed shape and draws the object by different layer with a liquid material.
- The powder bed process is processed from the raw material in powder form. The individual layers are each made up of a pinch of powder. In the case of plastics such as polyamide or metals such as steel and titanium, a laser melts or heats the individual powder granules with pinpoint accuracy. In technical jargon, these processes are called Selective Laser Melting (SLM) and Selective Laser Sintering (SLS).
To produce a spare part by only the push of a button, Deutsche Bahn creates construction templates for 3D printing from existing drawings or scanned objects. The DB can produce components weighing over 17 kilos and suitable even for ICE trains. Printing takes about an hour for a coat rack or two days for a cable box. This means that this production method is particularly suitable for individual productions, but that it therefore becomes unprofitable from more than 100 pieces.
3D printing is also tested in stations: Braille handrail panels make it easier for visually impaired people to find their way around stations.
Partnership and professional training
Instead of setting up hundreds of expensive 3D printers themselves, Deutsche Bahn relies on a partnership with the Mobility goes Additive network. Over 40 companies – including universities but also start-ups – have come together to stimulate innovations in 3D printers. Printer manufacturers and print service providers, as well as Siemens and other partners, are also part of this partnership.
Mobility goes Additive (MGA), a German-based network headed by Siemens Mobility under the participation of Deutsche Bahn, and promoting 3D printing within transport, has obtained in december 2019 first-time approval for use of an additively manufactured brake suspension link for trains. This highly-loaded part is now in use at Hamburger Hochbahn.
BOStrab, responsible for the German Federal Regulations on the construction and operation of light rail transit systems, was also involved in the approval of the 3D printed part. As a result of this venture, a standard for future approvals will be developed by BOStrab to increase the application of 3D printed components and spare parts in the railway sector.
DB is also integrating 3D printing into vocational training for the first time this year. All around 200 young professionals who start their apprenticeship in one of DB’s twelve large maintenance plants in September 2019 will in future manufacture parts using the 3D printing process. Since commercial and technical training has not yet taken 3D printing into account in Germany, Deutsche Bahn has developed its own training content for this.
Standards and security
It is obvious that 3D printing must be the subject of a demanding normative and legal framework. 3D printing has developed rapidly in recent years and its potential for technological innovation includes hidden aspects with risks for security, for intellectual property rights, for criminal and human ethics. We will have to be attentive to 3D « pirated » parts, without quality standards, as we see in the automotive sector. At the standards level, it seems obvious that each part manufactured in 3D will have to obtain at least the same criteria of durability, wear and quality as the same original part leaving the factory.
3D printing has considerable development potential, which can help railway companies to deliver more reliable trains more quickly. Avoiding canceled trains or those which clogging up workshops is also an important criterion for promoting a modal policy. Trains that remain as little as possible in the workshop, they are also assets that bring more money …