From the Printer to the Rails

Maintaining and repairing trains needs to be done as quickly as possible so that the vehicles can be brought back into service without delay. In the future Siemens Mobility will speed up the procurement of spare parts – by using 3D printers that can quickly manufacture the parts in its maintenance depots worldwide. That cuts the fabrication time by up to 95 percent. This and further advantages of this new way of working can already be seen at the new Rail Service Center in Dortmund, Germany.


by Tim Schröder

Those who visit cities that have a tram or commuter rail system quickly notice that trains and streetcars tend to look very different from city to city. For example, some cities have low-floor trams with a very low entryway, while others have tram stations with high platforms. All different types of rail systems can be found because every public transport operator has its own unique requirements. Siemens also offers a wide range of rail-vehicle types and variants. However, this variety can make maintenance and repair operations at depots a challenge because it means that many different types of spare parts have to be used.


Public transport companies want to be able to service their rail vehicles quickly so they can get them back into operation as soon as possible – ideally within one day at the latest. This means that spare parts also need to be obtained quickly. Unlike the case with automobiles, however, rail-vehicle components tend to be complex in their design and are generally manufactured in small numbers. In other words, spare rail-vehicle components are usually only manufactured, cast, or milled as needed, and it can easily take several weeks or even months for such components to be delivered after they’re ordered. That type of time frame would be unacceptable for a public transport operator, however. 

Printing Instead of Warehousing

Up until now, Siemens Mobility – Siemens’ rail division – has prefabricated highly critical spare parts and for mobility applications and stored them at maintenance depots. As a result, the availability of spare parts for maintenance operations is currently nearly one hundred percent. The problem here is that such an approach is expensive, not least due to the fact that many of these parts and components are ultimately never needed. Siemens Mobility has therefore come up with a new idea: It plans to gradually equip its maintenance depots with state-of-the-art industrial 3D printers that can manufacture spare parts in just a few hours. The division has already installed a 3D printer at its new maintenance depot, the RRX Rail Service Center, which Siemens Mobility opened in Dortmund in the spring of 2018. The maintenance center has already printed spare parts and components for Düsseldorf Airport’s SkyTrain, a suspension monorail from Siemens that connects the airport terminals. The 3D printer also produces individual tools and devices needed for the trains. 

“Over the next few years, we will establish a complete network of digital printers at our various locations worldwide."

“Over the next few years, we will establish a complete network of digital printers at our various locations worldwide and link them with our headquarters in Erlangen, where we operate a Center of Competence for 3D printing,” says Michael Kuczmik, Head of Additive Manufacturing at Siemens Mobility. A total of 88 such maintenance projects are currently being conducted around the globe. “For some time now, we’ve been manufacturing spare parts in Erlangen and sending them to the various depots,” Kuczmik explains. Shipping takes time, however, and it’s clear that using 3D printers to manufacture parts at the depots themselves shortens the maintenance process. “The use of 3D printers at our depots marks a major step forward,” says Kuczmik, who along with his colleagues expects to achieve significant cost reductions as a result. Until now, for example, it was necessary to order a minimum quantity of components from a supplier. In addition, the use of 3D printing reduces the amount of warehouse equipment needed while also ensuring that spare parts can be made available more quickly. Still, the facility in Dortmund is not completely self-sufficient. “We continue to engineer the spare parts here in our Center of Competence with NX software from Siemens, for example,” Kuczmik explains. “We then send the data to Dortmund, where the part is printed.”

Finished Components Instead of Prototypes

Siemens already has extensive experience with additive manufacturing. Corporate Technology, the central research and development unit from Siemens, procured its first 3D printer before many other companies – in 1989. Siemens Power Generation introduced its first 3D-printed component – a burner tip for gas turbine burners – to the market several years ago. “That was a signal for us at Mobility,” says Kuczmik. “We began to think that if additive manufacturing could be used for such an extreme application, it could also be employed to produce safety-critical rail system spare parts and components.” Mobility initiated a 3D-printing feasibility study just over five years ago. Since then, the division has been designing and manufacturing metal and plastic components in Erlangen.


The experts in Erlangen initially had to address a significant challenge, however, as there was no industrial standard at the time for rail-system components produced with additive manufacturing techniques. “We therefore conducted extensive studies and spent an entire year developing the 3D printing process to a point at which we could ensure that it would operate in a stable manner and produce parts of consistently high quality,” Kuczmik explains. Their work convinced the TÜV Süd technical inspection association, which certified Siemens Mobility, along with only one other manufacturer in Germany, as an “industrial supplier of additive manufacturing services.” “We continue have to keep in mind that 3D printers are often only used to manufacture prototypes,” says Kuczmik. “We, however, utilize them to produce what are in some cases safety-critical components that are ready for use under the rough conditions of everyday operations.”

The facility in Dortmund initially only printed plastic components because the industrial printer from Stratasys that’s used for this purpose is easy to operate. However, the machines used to print metal components require specialized knowledge to operate, so they’re currently only used in Erlangen. The printer in Dortmund operates in accordance with the fused deposition modeling technique in which plastic is melted layer by layer and so grows into a 3D structure. “Stratasys is considered to be the original developer of this method, and we believe this system is the most advanced,” says Kuczmik.


Plans now call for the fused deposition modeling method to be used also to manufacture rail-vehicle interior paneling components in Dortmund. Such paneling may be needed, for example, if rowdy soccer fans go on a rampage in a train or tram after a match and there are no replacements in stock. “The RRX Rail Service Center in Dortmund guarantees its customers a high level of rail-vehicle availability,” says Kuczmik. “That means we have to get rail vehicles up and running and back to the customer as quickly as possible.” This principle applies not only to regular maintenance but also unexpected events such as accidents or vandalism. Plastic 3D printing allows the experts in Dortmund to repair damage quickly. It used to take as long as several weeks to manufacture a spare part – but the 3D printer can now produce such components in just a few hours. Or in other words: This solution cuts spare parts fabrication time by up to 95 percent. 


Plans call for additive manufacturing to soon be used for rail-vehicle maintenance in the U.S. and Russia as well. Spare parts for American rail vehicles are still printed in Erlangen and shipped to the U.S. “We’re going to speed up the process in the future, however, by installing printers in the U.S. that will expand our growing network,” says Kuczmik. 


Tim Schröder 



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