Additive manufacturing: there’s no going back

A new phase has been reached in the development of additive manufacturing (AM): techniques such as 3D printing are now increasingly enabling complex components to be designed and reliably manufactured that can achieve a level of performance not attainable by conventional manufacturing. Examples of this new “value driven” era for additive manufacturing are 3D printed combustion components to be used in Siemens’ new HL large frame gas turbines, and to be deployed at Keadby 2 in the UK, as well as for the Lincoln County peaker and Morrow repowering projects in the USA.

“You couldn’t make these parts conventionally”, says Markus Seibold, VP, AM, Siemens Power and Gas, “so there’s no way back. And we have enough trust in the technology that we are using it even in the HL.” In fact, he points out, “you couldn’t get to all of the performance features of the HL if it were not for these 3D printed components.”

Seibold was speaking at a media event in December 2018 to mark the opening of a new state-of-the-art 3D printing factory at the Worcester, UK, site of Materials Solutions.

The opening of this new factory can be seen as an important step towards Siemens’ goal of fully industrialising additive manufacturing (in which components are built up layer-by-layer from ‘sliced’ CAD models (or ‘digital twins’), typically by melting/sintering of metal powders with precision controlled high power fibre lasers).

Materials Solutions, founded in 2006 by AM visionary Carl Brancher, has pioneered the use of selective laser melting (a 3D printing technique) for the manufacture of high-performance metal parts, in particular high temperature super alloys (Ni/Co/Ti), notably nickel alloy 247, said Phil Hatherley, general manager, Materials Solutions. The focus of the company to date has been on high-end prototyping and serial production for applications in a range of demanding industries including aerospace, motorsport/automotive (eg, conformally cooled tooling for engine block manufacture), as well as power generation, with over 5000 parts supplied to around 80 plus customers worldwide. Siemens acquired a majority (85%) interest in the company in 2016 and it is now 100% owned by Siemens.

Siemens says its investment of €30 million in the new Materials Solutions facility will “enable the growth of the business by doubling the number of 3D-printing machines to 50 and will also increase its post-processing capabilities.”

With power generation applications accounting for about a third of the new factory’s business, Siemens believes there is considerable scope to leverage the in-depth expertise it has acquired as a user of 3D printed components in its own machines to benefit external customers via Materials Solutions.

By employing industrial methods to scale up production, Siemens aims to bring down the costs of AM by serial manufacturing of high-end complex metal parts in a fully digital “robust industrial environment.”

The new factory has a footprint of 4500 m2 and is adopting what is described as a “true industrial approach, housing multiple machines across a shop floor”, with a mezzanine concept for handling the metal powders. The parts move through a variety of processes, with engineers ensuring that they are compliant. The digital approach embedded in the factory site creates “a modern digital factory and provides end-to-end service to customers”, says Siemens, employing many of its latest digital factory and AM technologies, including an end-to-end PLM (product lifecycle management) chain, Siemens’ computer-aided design software, NX, and MindSphere, the Siemens cloud-based, open IoT operating system that “connects products, factories, systems, and machines with data analytics.”

The facility is employing principally 3D printing machines supplied by EOS (eg M270, M280, M290, M400, and M400-4 (the four denoting four lasers)), and also has a Renishaw 500Q. Siemens has developed a close relationship with EOS, providing software, automation technology and drives, as well as working on the co-development and industrialisation of future 3D printing machines. Siemens is also partnering with Solukon on an advanced system for removal of metal powder from complex internal cooling channels inside components.

As well as the Materials Solutions investment, Siemens is significantly expanding AM activities at its Finspång site in Sweden, with a focus on repair and serial production in support of Siemens-supplied power generation equipment and plans to substantially increase 3D printing capacity there (from 15 machines (EOS) currently to around 60). The company in addition has a 3D printer (EOS M400) in Charlotte, USA, two in Berlin (EOS M290 and EOS M400-4), and has established what it calls the Additive Manufacturing Competence Center, in Erlangen.

Additive benefits

Siemens took its first major step in additive manufacturing in 2009 when approval was given to the purchase of a selective laser melting machine (M270) from EOS for installation at Finspång.

Significant 3D printing milestones achieved by Siemens since then have included:

• 2013. Burner tip replacement for SGT-800 gas turbines. 3D printing then used to provide burner repairs and components (burner tips and swirlers) for SGT-700 and SGT-800 gas turbines. Components that used to consist of a dozen parts reduced to a single (3D printed) part. 90% lead time reduction. 30000 EOH fleet experience. Swirler design only achievable by 3D printing. 
• 2016. Additively manufactured SGT-1000F burner head in commercial operation at power plant in Brno, Czech Republic, achieving over 8000 engine hours, demonstrating the concept of “spare parts on demand” (created as needed by 3D printing rather than being stored in a warehouse). Lead time reduced by around 50%.
• 2016. 3D printed impeller for a fire protection system water pump installed at Krsko nuclear power plant, Slovenia (replacing an original component dating from 1981).
• Early 2017. Successful full load engine tests of SGT-400 gas turbine stage one blades produced entirely using additive manufacturing. These blades operate at temperatures of up to 1250°C and experience 11 t pull.
• 2018. SGT-700 burners “designed for additive manufacture” achieve over 8000 hours at E.ON’s Philippsthal combined cycle plant. The first burners produced by Siemens’ intelligent burner manufacturing (IBUMA) programme based in Finspång, each burner head is 3D printed in one piece, rather than the 13 parts and 18 welds of the conventional design. Design improvements, such as making the pilot-gas feed part of the burner head instead of the outside fuel pipe, allow the operating temperature to be kept lower, with improved component and gas turbine life. This was a joint effort with E.ON.
• 2018. 3D printed sealing rings installed on SST-300 steam turbines in India.

In total, Siemens says it has now gathered more than 110 000 hours of engine experience with 3D printed gas turbine parts in fully operational power plants.

Vladimir Navrotsky, CTO Siemens Power Generation Services, who can be seen as another additive manufacturing visionary, recognised early on that 3D printing should be applicable to the intricacies of gas turbine manufacture and was the driving force behind the 2009 decision to invest in 3D printing (which was not without resistance at the time).

Speaking at the Materials Solutions event, he likened AM to the growth of a snowball, building on itself. Usually in technology development “if you improve one area you expect some sort of negative feedback in another area”, but in the case of additive manufacturing “more or less everything is going in the positive direction.”

Among the many mutually reinforcing benefits of AM he lists:

• Dramatic reduction in development schedules and reduced time to market for new products, with faster prototyping, ability to try out radical new ideas (“if you can dream it we can print it”), reduced development risks, and increased reliability of the final component/product. There are for example almost unlimited possibilities for design of internal passages and structures within components for better heat transfer, improved cooling (eg, turbine blades) and fuel/air mixing (eg, burners).
• Ability to manufacture more complex and “smarter” components, with, essentially, a severance of the link between cost and complexity. In fact “the more complex the better”, as manufacturing costs are pretty much the same.
• Improved quality, with better traceability and full process transparency, thanks to monitoring and analysis of each layer during the layer by-layer manufacturing, basically “integrating quality into the manufacturing process” and constituting a “closed loop” quality system.
• Increased flexibility to respond to market requirements, in terms of both product design and manufacturing (with “individualised” serial production). “There is no way back to the way we used to design in the past.”
• Capability to provide “spare parts on demand”, as already noted.
• Improved energy and resource efficiency at the manufacturing stage.

At the same time Navrotsky also cautions that the applications to be targeted by 3D printing need to be prioritised carefully. For example, gas turbine hot gas path components tend to be complex, and therefore selective laser melting manufacturing techniques are worth pursuing, whereas compressor blades currently look like less promising candidates because SLM could make them expensive, “like a compressor made from gold” (but other additive manufacturing techniques might prove cost effective).

For gas turbines, Siemens is currently focusing its additive manufacturing development efforts on burners, swirlers, nozzles and mixers in the combustion system and turbine heat shields, blades and vanes. For steam turbines the current focus is on steam path, seals, valve parts, bearings and shaft ends.

As designers get to grips with the potential of additive manufacturing and develop components specifically with AM in mind we are going to see some radical rethinking of familiar components. Navrotsky mentions gas turbine blades, and also completely new gas turbine burner concepts employing, eg, lattice structures only achievable with AM and optimised for mixing natural gas and hydrogen, enabling an SGT-800 turbine to run on 60% hydrogen, for example.

We are only at the early stages of appreciating what additive manufacturing can achieve.