Advanced Materials series: How can rail utilise additive manufacturing and 3D printing?

Additive manufacturing produces objects by printing them one thin layer at a time. It is favoured by designers and engineers for the way it allows complex structures to be produced simply, quickly and cheaply. Among its many applications are producing prototypes, lightweight or customised parts.

Latest update: February 2019

The Rail Industry is also adopting 3D printing applications. These include printed components for rail maintenance, which reduce the volume of stocktaking and the delivery of trains on the track, as well as components of rolling stock such as arm rest and seat back table. An advancement in terms of R&D introduced by Mitsubishi Electric Research Labs is 5D printing. This allows printing objects from 5 different axes, resulting in a 25% saving of raw materials and a final product able to better withstand to mechanical stress. At the same time, scientists at GE are developing a new 3D printer which also integrates the cold spray technology allowing for a faster manufacturing.

What is Addictive Manufacturing?

In contrast to current mass production manufacturing techniques where materials undergo subtractive manufacturing, additive manufacturing (also known as 3D printing) denotes a group of technologies where end products are built by layer upon layer addition of material. Originally used for rapid prototyping applications, additive manufacturing is now more widely used as it allows a greater freedom of design and produces lower-weight components. Additive manufacturing uses a minimum amount of raw materials and is a lot faster in comparison to subtractive manufacturing methods where a lot of material that has been machined, goes to waste.

Scale model of the Eiffel Tower printed with 3D-printing technology

Is it already in use?

The number of industries interested in additive manufacturing is constantly growing. Today, the list of industries adopting additive manufacturing includes:

  • Automotive for creating entire cars, complete chassis, and internal fittings; 
  • Aerospace for manufacturing aircraft components; 
  • Construction to fabricate construction components or entire buildings;
  • Medical to print silicone prosthesis as well as high-dose medications; 
  • Fashion where designers are experimenting with 3-D printed clothes as well as jewellery; 
  • Food to create fresh and healthy dishes in a fast and decorative way; 
  • Art to create sculptures and decorative patterns.

This variety of in-use applications demonstrates that this technology is no longer just a concept, but an established manufacturing method valued for its simplicity and environmentally friendliness.

How will it impact the rail industry?

Additive manufacturing’s on-site production and customisation capabilities could be beneficial for maintenance activities and the replacement of damaged and obsolete parts. Transport and storage of spare parts could be reduced or even eliminated. Siemens Mobility launched its first digital rail maintenance centre in 2018 where 3D printing is employed to manufacture components, cut stocktaking and bring trains back on track faster.

The use of additive manufacturing could also be used in the infrastructural design. For example, Crossrail is 3D printing curved wax moulds for concrete casting which is being used to form the station panels. This has reduced costs in preparing specific moulds for differently shaped panels. 

Additive manufacturing could enable the rail industry to design optimised shapes for components of rolling stock. Angel Trains, ESG Rail and Stratasys have collaborated to produce 3D printed interior components such as arm rests, grab handles and seat-back tables.

What should the rail industry do?

The rail industry should carry out a cost benefit analysis comparing both subtractive and additive manufacturing techniques, to gain more clarity in the cost savings associated with additive manufacturing. The rail industry could identify opportunities to transfer additive manufacturing technologies from the aerospace and automotive industries, where there is a larger use of additive manufacturing. Moreover, further research should be carried out to find opportunities to employ additive manufacturing techniques trackside

What R&D is underway and what uncertainties remain?

Rapid liquid printing, an alternative method developed by MIT’s Self-Assembly Lab in collaboration with Steelcase, physically creates objects in 3D space in liquid gel suspension, enabling the precise creation of customised products. This could improve the finish of products which is a current issue associated with certain methods of additive manufacturing. 

Deutsche Bahn are carrying out research in finding ways to use 3D printers in large warehouses to print spare parts for clients, reducing the number of items that would have to be stocked. 

The University of Birmingham and RSSB evaluated the feasibility of using autonomous robots for wheelset reworking. This was achieved by looking at automating inspection techniques with 3D printing to add material back onto the surface of wheels to repair damages.

Scientists at GE Global Research are working on ways to use cold spray for 3D printing. Cold spray is a coating deposition method which uses a supersonic nozzle to spray metal powder on the surface of an object forming an entirely new layer, without changing the original mechanical properties. This new printer will allow 3D shapes to be created quickly as cold spray is accelerating particles.
Mitsubishi Electric Research Labs (MERL) have developed a technology which allows objects to be printed from five axes, as opposed to one point like traditional 3D printers, also called 5D printing. This method creates products more resistant to mechanical stress. The method uses 25% less raw material than normal 3D printing technology. 

While the number of personal printers has risen, additive manufacturing is still an expensive and time-consuming process. The technological and economic constraints could make additive manufacturing unsuited for mass production. 

Low cost materials are usually used in the rail industry which make use of subtractive manufacturing techniques creating a lack of clarity in the cost savings associated with additive manufacturing. 

A lack of experience in 3D printing is another uncertainty, there is an issue of quality assurance of parts manufactured using additive manufacturing for example, surface finish can be in comparison to materials used in subtractive manufacturing. 

Moreover, the use of additive manufacturing for maintenance still requires further research. There is uncertainty on the suitability of additive manufacturing for outdoor maintenance works. 

Banner image author: Jonathan Juursema, via Wikimedia Commons.

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