The advantages of 3D printing spare parts for the rail industry
By adopting 3D printing technologies and high-performance materials, rail vehicle manufacturers can achieve significant cost savings. Jake Holmes explores the advantages of the additive manufacturing spare parts market for the rail sector
The upkeep and maintenance of railways and rail vehicles can cause significant downtimes, resulting in loss of revenue and high costs for rail operators. Having effective systems that can prevent downtime and improve the speed of maintenance is therefore crucial. Additionally, all rail vehicles – whether a tram, passenger train, high-speed train, freight train, or subway – require precisely designed and tested parts made of certified materials.
This is where 3D printing has been making its mark for several years, enabling rapid prototyping, tooling, and spare parts for wear and tear components production according to industry standards.
Railway assets tend to have a lifetime range of 20 to 40 years for electrical and mechanical systems, meaning rolling replacements and upgrades are an absolute necessity. This is a significant cost to an operator, as on average rolling stock makes up 30% of lifecycle costs for a high-speed train – matching energy consumption costs (30%). By integrating 3D printing into their operations, rail companies can implement improvements that result in substantial time savings and reduced maintenance of rolling stock costs.
CERTIFIED MATERIALS ARE KEY
The rail industry has very specific fire safety rules and standards which describe how the materials used in rail vehicle construction should act when exposed to fire. Materials used in rail vehicles for the European market, for instance, must follow the rail standards EN45545-2 to protect passengers and staff against onboard fire risks.
Numerous 3D printing materials have been developed in recent years to comply with the standard. These include high-performance polymers, such as PEKK and PEKK-A by 3D printing filament manufacturer Kimya, and ULTEM 9085 by chemical manufacturer Sabic. Such ‘open market’ materials have already been widely used across the rail sector to deliver safe products while minimising production and compliance costs.
ULTEM 9085 is widely used in the rail, aerospace, and automotive industries, as its properties meet the requirements of the most demanding industrial applications. The combination of high chemical and temperature resistance, and flexural and tensile strength makes the material an attractive option for the rail industry. Moreover, it’s easy to machine and offers low flammability and toxicity.
Fused Filament Fabrication (FFF), as well as Selective Laser Sintering (SLS), are 3D printing techniques often used in the industry due to their ability to produce parts with high-performing thermoplastic qualities. SLS is a powder-based 3D printing technology that fuses material layers into a final part using lasers, while FFF is a material extrusion process, building an object by depositing melted material layer by layer.
SPARE PARTS ON TRACK
3D printing company Roboze delivers on-demand, just-in-time manufacturing of spare parts to the rail sector, reducing costs associated with storage and pre-ordering for operators. 3D printing allows several components to be integrated together, enhancing the original design of a component rather than merely replacing it.
In suitable applications, Roboze can replace metal with high-performance plastics, reducing weight by 50% which leads to lower energy and fuel consumption. The environmental impact of the overall rail vehicle is also decreased, as more lightweight components require less material during production. Roboze’s ‘digital warehouse’ contains digital blueprints of spare parts. So, only when a part is required is the blueprint sent for printing and the part produced. This process cuts cost and manufacturing times, while reducing the spare part inventory requirements for rail operators.
In terms of 3D printed materials, Roboze uses polypropylene for flapper replacements on train toilets due to its wide chemical compatibility, low weight, and impact resistance. The company replaces toilet drain pumps using Carbon PA because of its strong mechanical properties compared to aluminium AA1050A. Meanwhile, low FST evolution, UL94-Vo at 1.5mm and 3mm or 0.059in and 0.118in makes ULTEM 9085 a suitable material for 3D printed armrest replacements.
ARMED WITH AM
Kimya – the additive manufacturing (AM) division of technology company Armor – provides 3D printing materials and services for the rail industry. Kimya entered the railway parts arena in 1982 when a supplier ordered a small batch of polymer parts through its manufacturing service. The original mould no longer existed, so the parts had to be redesigned from scratch using a PEKK filament developed in-house at the research and development centre. 3D printing the protective covers using PEKK led to cost savings and reduced lead times.
No digital twin or mould was available for reference, so a single paper plan was used by engineers and an original part was made using PVC as a prototype. A PEKK SC version was able to be printed using the PVC plan and could be applied to end-use. The custom PEKK SC filament was used due to its ability to resist high temperatures, up to 260°C, as well as flame retardant capabilities, abrasion resistance, and chemical resistance.
ON THE RAILS
Many rail companies have turned to 3D printing in one form or another in recent years to fulfil their spare parts supply, enhance component design or improve the environmental footprint of their rail vehicles.
German railway company Deutsche Bahn, for instance, has taken advantage of 3D printing using Gefertec’s 3DMP technology. The process creates near-net-shaped metal blanks using wire as a raw material at fast speeds and has a build-up rate of 600cm3 per hour, making it suitable for steel, nickel-base, titanium, or aluminium. Gefertec’s technology boasts cost savings of up to 60% with nearly 100% material utilisation, borderline eradicating waste. The company uses 3yourmind software to enable digitising logistics.
Additionally, Gefertec’s technology has been deployed for the production of wheelset bearing covers for class 294 locomotives. The component was essential to the vehicle’s safe operation as without it, lubricant could leak from the wheel causing damage to the bearings. Despite this model being over 50 years old, the Arc605 from Rolf Lenk, a German machinery manufacturer, produced a replacement piece for the locomotive. The original cast for the wheelset bearing cover measured 374mm in diameter, 78mm in height, and weighed 11.5kg, taking up to nine months for delivery.
Gefertec’s arc605 system only requires eight hours to produce the component, rather than the nine-month lead time previously. The German federal railway authority’s materials laboratory tests consistently found the product to be of high quality.
Elsewhere, rolling stock manufacturer Alstom has also taken full advantage of 3D printing’s capabilities for its trains, with over 150,000 parts being manufactured this way. This process has seen a massive scale-up from its first introduction in 2016 when 3D printing wasn’t being used to produce parts for the company’s rail vehicles. Alstom now produces 40,000 pieces a year through 3D printing, both spare parts and new designs.
Polymers, ceramics and metals are the main focus points of Alstom’s 3D printing capabilities. Fire and smoke-compliant materials, EN45545 for Europe and NFPA130 for North America, are available within Alstom’s 20-strong validated polymer portfolio. Meanwhile, aluminium, stainless steel, high-performance steel and titanium are available for metal printing.
This range of materials allows the company to produce a wide array of products for rail companies, such as a headlamp case for a high-speed train in France, a part in a soft material to be installed into an air conditioning evacuation tube for a Spanish metro, a jig to ease screwing holes in car body shells in Germany, and a bogie steel cover in the Nordics.
PRINTING THE FUTURE
Using 3D printing for train repairs and spare parts can bring down costs and reduce downtime. Economically, 3D printing has massive advantages, as there is no minimum order required as well as no warehouse needed for spare part storage. Per unit, costs rise using 3D printing, but the total cost actually drops for replacement pieces as only small orders are required. The break-even mark for plastics is roughly 2,000 parts, whilst metals is 200.
Additionally, less scrap material is produced using 3D printing methods whilst they also use less energy, as only the quantity required is produced. Each tonne of CO2 produced in the future may come with associated costs, at which point 3D printing will provide a more CO2-friendly alternative to traditional manufacturing.
Looking ahead, 3D printing’s influence on the locomotive industry may stretch wider than just rail vehicles, as novel ‘Printfrastructure’ technology has been deployed in London on the construction of the HS2 railway line. Concrete has been ‘printed’ on-site using computers, rather than being transported as slabs, in order to build the infrastructure of the new train lines.