PIONEERED in the aviation industry as a means of reducing the weight of components, additive manufacturing, or 3D printing, is now a growing area of interest and development for rail.

German Rail (DB) is the latest company to explore opportunities to use 3D printing. However, it is not weight loss which the railway is looking to alleviate, but replacement of obsolescent components used in rolling stock and rail infrastructure.

3DMs Stefanie Brickwede, project manager for the 3D printing project in DB's control technology department, says the programme began in mid-2015 and has already produced more than 200 different components of 50 different types, some of which are now in use on DB passenger trains.

"We are not an OEM company, but we are responsible for maintenance and it is here where we think that 3D printing can help us," Brickwede says. "We initially approached the project from a top-down perspective, but this was not a success. So instead we initiated it from the bottom-up, by hosting road shows and visiting DB's 146 rolling stock workshops to ask engineers how they thought it could help them."

Among the products that have already been produced junction boxes positioned beneath trains, locks for tablets, propellers for radiator fans, dust caps, and oscillating levers. It is also proving beneficial in unexpected areas such as replacing worn-out components in vacuum cleaners used to clean ICE trains at depots.

"3D printing can solve our obsolescence problem," Brickwede says. "Most of the parts that we are printing are very old and often we cannot find a 3D file of the design - we are often lucky to get a 2D drawing. So instead we take all the specifications we can from the existing component to create a CAD file from which we can produce the component using 3D-printing."

DB now has seven full-time employees working on the programme with backgrounds in long-distance passenger, freight, infrastructure and logistics, while another 40 employees are also engaged with the project. "They all bring their own point of view and perspectives from different areas of DB, which is important for the project," Brickwede says.

However, DB is not yet producing 3D-printed components by itself. From discussions with colleagues working in the aviation industry, particularly at Airbus, about how it approached using the technology, Brickwede says they discovered that networks of various companies experienced in using 3D printing were established in order to share best practices and adapt the process for the needs of the manufacturer. DB subsequently set up its own network of nine companies at the beginning of 2016 to work on 3D printing for the rail industry called Mobility goes Additive.

Of the various additive manufacturing processes available, DB is using Selective Laser Sintering (SLS), which uses a high-power laser to fuse small particles of plastic into a three-dimensional mass, and Selective Laser Melting (SLM), a similar process which melts the particles rather than sinters them and is used by DB for metal. Generally the components used by DB are made from PA12 and Ultem plastics as well as aluminium.

Network member companies are among the suppliers of the components to DB (see panel), including Materialise, Belgium, which specialises in developing 3D printing software, EOS, which supplies machines, and Laser Zentrum Nord (LZN), a laser specialist which offers a printing service. Legal company Leupold Legal is also playing an important role.

"They specialise in IP rights, which is important to produce the CID file required to reproduce the component," Brickwede says. "OEM companies are worried that the integrity of their component might be jeopardised by poor copies as there is no guarantee.
We need to avoid this. We also need to make sure what we are producing meets existing certification standards."

These are not the only challenges with adapting 3D printing for rail. Brickwede says the rail industry requires significantly greater flame resistance of materials than in aviation, restricting the type of materials that it could use for certain components. There are also certain things that the process is not yet able to do.

"We were asked whether we could produce a replacement nose cone for an ICE train," Brickwede says. "Unfortunately the size of the component is too big to fit within our current capabilities. Also the carbon fibre material used cannot yet be produced using sintering, although trials are underway to produce fibre material in this way but these fibres are too short at present."

In addition, 3D printing remains a relatively expensive process, therefore restricting its current usefulness and widespread adoption. As a powder-bed process, SLM is particularly expensive and can prove volatile. An individual machine can also cost around e1m.

Yet Brickwede says that the technology is improving and evolving all of the time, and as it does DB is now well-placed to embrace it as a method that could improve its capability to replace rolling stock and infrastructure components quickly.

The next step for DB is to purchase its own machines and Brickwede says it is planning to install two units at Fulda in central Germany. "This is a maintenance workshop that deals with spare parts, and especially braking systems," she says. "It is also the location of our internal education provider, DB Training, so we will be able to combine the production process with training our engineers."

A year into the project, Brickwede admits that DB, and her team, are still exploring what is possible with 3D printing. However, she says ultimately
3-7% of the spare parts that the railway needs for both rolling stock and infrastructure could be printed in-house.

While this might not seem like a lot, she says from an obsolescence point of view it is potentially a game-changer, and as the technology improves, this figure could conceivably increase.

"We won't print everything but every product and technology has a different need," Brickwede says. "3D printing is a new way of meeting this need."