Often based along dangerous coastlines or nearby safe passages to land, the lighthouse is at once a structure to aid maritime navigation and a metaphor for risk, guidance and direction. In their evolution from hilltop fires to constructed towers with electric light, perhaps we can add improvement in function and performance to that list too.
Siemens Mobility, in its application of additive manufacturing (AM) for the rail industry, can relate to many of those characteristics.
It was 2013 when the company started to pull together six project leaders, all with engineering expertise; five support staff, with responsibilities ranging from application management and logistics; and six manufacturing engineers, to additively manufacture what would become more than 13,000 spare parts for the sector in seven years. Many of its street cars customers were then gathered to take in a presentation, where Siemens would make its pitch.
In this meeting, where the potential to shorten the turnaround times for replacing components that are several decades old and often hard to procure was discussed, a representative from SWU Verkehr outlined how they wanted to alter the design and functionality of their tram drivers' armrests. They asked whether it would be possible to 3D print such a component.
It was. And it became the first of 1,300 designs that would not only meet the necessity to replace components but align with Siemens Mobility’s idea to advance parts at the same time. Siemens’ Sparovation – a portmanteau of ‘spare’ and ‘innovation’ – programme was born.
“If you touch a part which is 30 to 60 years old, and we change the production method and sometimes also the material, you have to do the complete approval by the newest standards regulations,” explains Michael Kuczmik, Siemens Mobility Head of Additive Manufacturing. “If our designers have to do the engineering and consider the new standards and regulations, then we said, okay, we [might as well] improve the part.”
Siemens would come to learn how, as a general rule, the certification of ‘first of its kind’ replacement components would require more time – sometimes the best part of a year – for certification to be granted. There have been other instances, however, where extensive research and development hasn’t been required and newly certified spare parts have been delivered within just nine days. Of course, these lead times are one-offs – once certification is granted, a spare part that required months of engineering work and then spent months in the certification process can be continually delivered in the time it takes to manufacture, finish and ship. And the less time the better, for Siemens has some customers who are losing thousands of Euros a day on idle vehicles at the depot.
For some companies, like SWU Verkehr, those thousands a day mean much more than compared to some of Siemens’ larger clients like Deutsche Bahn. SWU operates fleets of ten Siemens Combino NGT UL trams and twelve Siemens Avenio M NGT 6 UL trams in the cities of Ulm and Neu-Ulm, meaning one idle vehicle represents around 5% of its fleet and 5% of its revenue within its tram service offering. Per the company’s Head of Rail Vehicles Jürgen Späth, SWU 'simply cannot afford' to shut down a vehicle because a replacement part is missing. But while the urgency of installing spare parts and getting trams back on the rails is paramount, there’s an understanding how improving the parts as they’re replaced makes sense in the long run.
Siemens Mobility
Suspension bracket of a dt4 brake calliper unit. Siemens Mobility
Suspension bracket of a DT4 brake calliper unit.
The company, who has been working with Siemens since 2003, started out on its implementation of 3D printed parts with the updated driver’s armrest raised in the initial meeting, which would go on to feature three additional operational controls, channels for cables to run through, an increased stiffness to guard against future damages, assembly aids for long screws, more stable wiring harness routing, integrated cable fixation, and part and serial numbers for part identification and traceability. All were implemented after an assessment of the traditional part, with Siemens leaning on judgements from its customers and its rail design and maintenance departments. It is a key part of the process.
“[Our six project leaders] look into the conventional design and try to understand what the reason for the failures was – what can be improved?” says Kuczmik. “With additive manufacturing, there’s a really high freedom of design. And my team is in contact with Siemens’ designers of new vehicles, they have a close exchange to really understand the newest standards and regulations with the experience we have at Siemens. And in the end, there’s a product which is definitely better than a part which is 30 to 60 years old. This is the advantage of Siemens as a designer, maintainer and spare parts supplier.”
Another instance in which SWU leveraged that experience was to make improvements to the exterior of a tram vehicle. Since SWU’s trams navigate through busy cities alongside bustling road traffic, there are, on occasion, collisions between tram and car. A quick and easy improvement to the tram’s front skirt, SWU posited, was a day running light which would help to make the vehicle more visible to other road users.
“'Yes, we can do that,'” Kuczmik remembers telling his colleagues at SWU, “’but maybe we can change something else.’
“We called [SWU] for a co-creation process and they said the typical accident is a car from the right side at the front, because it’s turning to the left. They [typically] change the complete front skirt instead of only the small, damaged part. So, we split the front skirt into three pieces, with a lot of small fixtures added for the cable of the day running light, and so now the customer only has to change one third of the complete front skirt [in the event of a collision].”
Both of these applications have been additively manufactured using Fused Deposition Modelling (FDM) technology: the armrest with a ‘low-cost’ polymer and the front skirt components with a high-performance polymer boasting the ‘highest level of fire retardancy’, ‘more mechanical properties’ and the ability to endure ‘very high wind loads.’
Siemens hasn’t just limited its adoption of 3D printing for rail spare parts to polymer or FDM, however. The company has also invested in metal powder bed fusion technology and is producing spare parts in aluminium and stainless-steel materials. “There’s no limit in respect of safety, if we do everything in terms of approval, material properties, qualification and so on, in the right way,” says Kuczmik, also noting how because of the company’s deep expertise and experiences in the rail space, Siemens obtains immediate trust from most companies.
Such trust was evident at Hamburger Hochbahn last year when a suspension bracket of a DT4 brake calliper was replaced with an additively manufactured version that received approval by the component manufacturer, rail operators and corresponding certification bodies. Functioning in a similar way to the conventional component with an adequate level of safety, the stainless steel suspension bracket has been designed to deflect the braking forces away from the brake calliper unit into the bogie frame, meaning it must withstand a braking force equivalent to several tons. During testing, it was exposed to a strain of more than 25 tons and demonstrated a lifespan of 45 years, with Siemens now in the process of suggesting the part to Deutsche Bahn and, later, customers in Austria, Switzerland and France.
Having taken the calculated risk to invest in AM for this endeavour back in 2013, Siemens Mobility, through the additive manufacture of 13,000 spare parts from 1,300 certified designs, continues to guide and direct its customers to significant cost savings via quicker turnaround times. Along the way, and thousands of times since they embarked, parts have not just been replaced but they’ve been improved. For Siemens Mobility, the impact AM is having in the rail sector is palpable.
“I think there’s a lot of expectations on these technologies because additive manufacturing seems to be something of a lighthouse in our industry," Kuczmik finishes. "We have a lot of vehicles, a lot of different designs, a lot of problems on obsolescence: the parts can’t be delivered anymore. And with very low quantities, additive manufacturing seems to be a tool to solve this issue. It’s a big improvement for our industry.”
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