Martin has led the RAILiability working group in MobilityGoesAdditive for the last two years. RAILiability is a group of European railway operators working together to advance Additive Manufacturing within rail, sharing their best practice and collaborating on resolving the core challenges.
Why is obsolescence such an issue for the rail sector?
Rail vehicles are expected to run in passenger service for over 35 years. Unfortunately, the components and parts that make up these vehicles often become obsolete way before the vehicle has life expired, either because the supplier no longer exists, no longer manufactures or support these parts, or the original designs have been lost. This can create huge issues and costs for our sector. It is notable that 65% of the UK rail fleet is over 10 years old, 25% over 25 years, with an average vehicle age of 17 years. Technology and manufacturing processes can change considerably over a 17 year period, for example 17 years ago there was no iPhone, no Twitter and no Amazon Prime with next day, never mind same day, delivery!
To keep older rail fleets operational and in peak condition, asset managers such as Angel Trains need to ensure the continued supply of parts; parts that may well be obsolete or be required in very small quantities.
Low volume parts are a real struggle for the existing supply chain and traditional manufacturing methods, leading to many operators receiving an unsatisfactory service. Also, legacy parts are generally expensive, have very long lead times, and are often not tailored for the specific fleet or application. Production times can be exacerbated by external issues such as the pandemic, the war in Ukraine and Brexit. Order quantities are also often an issue, and an operator or fleet owner may be required to order, and then store, hundreds more parts than they require, or will ever require for the remaining fleet life. For example, we recently looked at remanufacturing a custom aluminium extrusion, the supplier for which had a minimum order quantity of two tonnes! We only actually needed a single 40kg extrusion.
What is digital manufacturing and how can it address obsolescence?
Digital manufacturing is the design, development and production of physical parts using computer aided processes, such as CAD, Additive Manufacturing (AM, also known as 3D printing) and programmable CNC machines. Digital manufacturing eliminates the need for 2D drawings, reducing the time to production and ensuring the repeatability of production.
Some of these digital manufacturing technologies and processes are not new, but the way that we have been applying them to the UK rail industry is. Primarily our focus has been on addressing obsolescence. If our customer has a part that they cannot source anymore, or if they can source the piece, but the price is high due to traditional techniques requiring the production of patterns or moulds; or maybe there is a 12-week wait for the component; or perhaps excessive minimum order quantities, even though they only require a few parts, then DB ESG and digital manufacturing may be the solution.
Digital manufacturing has many advantages over traditional production methods:
- You can replace parts in a matter of days, rather than the months it usually takes to replace parts using traditional manufacturing processes.
- The cost for short runs of these parts can also be reduced; there is no need for costly jigs or fittings, no minimum order quantity requirements and therefore no need to order and then store parts than are not required.
- The opportunity can be taken to make design improvements, thereby improving the reliability and quality of the parts, incorporating newer materials and technologies (see examples below).
- Train operators can also have the freedom to customise train interiors cheaply and quickly.
Coming back to design improvements that can be made, I can give you some examples of this. Firstly, for Transport for Wales and their Class 158 blower fan, the original aluminium sheet metal welded design kept breaking. We successfully re-designed this fan, using a combination of CNC and additive manufactured parts. The rotor was produced in AMT smoothed ULTEM 9085 black, providing great strength and resilience to fatigue failure.
Another example, we worked for Transport for London on a Proof of Concept to re-engineer a cab handset, for the S-stock fleet of London Underground trains, a complex multi part assembly that was repeatedly breaking. We modified the design to remove the common failure mode, making it stronger and better suited for the environment. Manufactured in SLS nylon, dyed black and smoothed, the final revised part was very well received. This demonstrates that parts can be designed to meet their requirements, rather than be limited by specific, or traditional manufacturing methods.
In addition, once a part has been produced using digital manufacturing and we have ensured that it meets all the relevant standards, if this part is ever needed again, then it could be ordered and supplied very quickly for a cheaper price than the initial cost. This is because all the reverse engineering, design work and approvals will have already been carried out. To support our customers, we have created a digital inventory (catalogue) of parts, all held in one place, making it easier to obtain additional parts on-demand.
What is DB ESG’s digital manufacturing experience?
Since 2018 we have been developing our knowledge in this field and hence have acquired extensive experience in digital manufacturing for the UK rail sector. We have been working in collaboration with the rolling stock asset management company Angel Trains, with a particular focus on the provision of obsolete components in support of their assets.
Our collaboration with Angel Trains initially focused on Fused Deposition Modelling (FDM) technology, as it is one of the most established 3D printing processes for robust, industrial applications, with parts already deployed, in service, in comparable transport industries, such as aviation.
DB ESG and Angel Trains were the first in the UK to use this FDM technology to produce 3D printed replacement parts, which were put into commercial service on a passenger train, namely seven grab handles and four armrests.
These parts were finished to such a standard that they were indifferentiable from the original components. The parts were fitted to a Class 165 train owned by Angel Trains and operated by Chiltern Railways in the summer of 2019. A visual inspection of the parts was conducted one year later, and the parts remain in operation to this date.
Since then, we have rapidly expanded into the supply of digitally manufactured parts for the purposes of prototyping, tooling, and final part manufacture. We now have several suppliers that can provided traditional methods of manufacture, such as CNC and laser cutting, plus we have AM suppliers (Selective Laser Sintering (SLS), Multi-jet Fusion (MJF), Stereolithography (SLA) and FDM technologies) and we are advancing in metal printing. We now also have a wide variety of post processing options, including chemical smoothing or vibro tumbling to create smooth finishings in the natural colour, dyeing or painting, and electroplating. The final parts can be indistinguishable from the existing ones.
Our digital manufacturing process
Typically, the required part is 3D scanned and reverse engineered, or recreated from drawings, if available. The most suitable manufacturing process is identified e.g. 3D printing or CNC machining etc., to enable the most cost-effective solution, that meets the requirements and minimises risk. The raw scan files are converted to editable 3D models for further development (if required). Consideration is also given to the compliance requirements for the component, for instance fire and structural analysis are fundamental considerations, and assessed for each component, taking account of the operational environment.
Prior to final production, a non-rail-grade prototype can be produced, and a trial installation undertaken. This has been found to be a really beneficial step. For example, when we produced the grab handles for Chiltern Railways, during the trial fit we discovered a high level of seat shell variation and the designed part did not fit several of the seat shells. If traditional manufacturing methods had been used, a complete rework of the project would have been required, at significant expense and time delay. However, because we were using our digital manufacturing approach, the design could be quickly altered, and the seat shell design variants be accommodated. The design therefore went through several design iterations, using prototypes, 3D printed, from lower grade materials (both prototype handles and prototype inserts). Through the prototyping and testing stage, the design was refined to include captive fasteners that allowed a degree of adjustment on installation. These ensured that the handles always fit perfectly to the highly variable seat shells.
Following prototype testing, final 3D models and engineering drawings are produced, and the final component is manufactured.
We believe that digital manufacturing is already transforming the manufacturing sector, making it more sustainable, more efficient, and less wasteful.
Challenges such as obsolescence should be banished into history, making our sector much more innovative, responsive and technology driven than ever before.