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Additive Manufacturing for Serial Production of High-Performance Metal Parts PUBLIC ACCESS

Markus Seibold Vice President Additive Manufacturing Siemens Gas & Power

Mechanical Engineering 141(05), 49-50 (May 01, 2019) (2 pages) Paper No: ME-2019-MAY5; doi: 10.1115/1.2019-MAY5

Additive manufacturing (AM) is a process that builds parts layer-by-layer from sliced CAD models to form solid objects. Just a few years ago, 3D printing was primarily used for rapid prototyping. Due to improvements in performance, AM has the potential to become a new key technology for serial production. Innovative advances like selective laser melting (SLM) enable the manufacture of high-performance metal parts. Modern printers contain several lasers, which enables the production of multiple parts at the same time. AM includes much more than just 3D printing: It’s an end-to-end process, from design and simulation to 3D printing to post-processing.

Additive manufacturing (AM) is a process that builds parts layer-by-layer from sliced CAD models to form solid objects. Just a few years ago, 3D printing was primarily used for rapid prototyping. Due to improvements in performance, AM has the potential to become a new key technology for serial production. Innovative advances like selective laser melting (SLM) enable the manufacture of high-performance metal parts. Modern printers contain several lasers, which enables the production of multiple parts at the same time. AM includes much more than just 3D printing: It’s an end-to-end process, from design and simulation to 3D printing to post-processing.

Siemens has been investing in AM technology right from its inception. With the opening of the new AM facility at Materials Solutions Ltd. in Worcester, UK, in mid-December 2018, the company is continuing to drive the use of AM for serial production, with a focus on high-temperature super alloys. The company is using the technology in-house for turbine components, and also provides solutions to fully digitalize the process, from design and engineering software to simulation tools and full machine and shop-floor automation for the aerospace, automotive, and other industries.

The solutions for hot gas-path gas turbine components illustrate the potential of AM in serial production as well as the service business for both repairing components and manufacturing spare parts. In the area of rapid repair, in 2013 the burner-tip repair for industrial gas turbines of types SGT-700 and SGT-800 was the first commercially established method of repair for industrial gas turbines using AM. The SGT-700 has a simple cycle power output of 33 MW whereas the SGT-800 has a capacity of 57 MW. During operation, these components suffer thermomechanical fatigue, damage, and wear, especially to the burner tip. The conventional repair procedure required prefabrication of a large portion of the burner tip, which was then used for replacement after a specified burner operation period. AM machines have been customized to adapt to these kinds of repair scenarios. The newly implemented repair route via AM is about ten times faster than the conventional procedure, because it avoids quite a few manufacturing and inspection processes.

In the area of spare parts on demand, the axial swirler for the pilot burner in the Siemens gas turbine SGT-1000F combustion system was already serialized in 2016 and has accumulated over 11,000 operating hours in commercial operation since then. Previously, this kind of component was produced by investment casting. Instead of requalifying the existing cast vendor or performing a full qualification of a new vendor, a choice was made to produce the swirler using AM. Because the annual demand for this component is relatively low and can vary greatly, business case calculations clearly proved the benefit of changing the production technology to AM.

In 2017, Siemens began printing entire gas turbine burners using SLM. Each burner is now additively manufactured in one piece, compared with conventional manufacturing methods that required 13 individual parts and 18 welds. Design improvements—like the pilot-gas feed being part of the burner instead of the outside fuel pipe—allow the operating temperature to be lower, which contributes to a longer operational lifespan of the component and, ultimately, the gas turbine.

Just recently, the first gas turbine blades ever produced using AM have successfully finished performance testing under full-load conditions. The blades withstood an acceleration of 10,000 g while being exposed to temperatures up to 1,250° Celsius. The main reason for this breakthrough was the design freedom that AM offers: Should the cooling channel inside a component meander through the material instead of crossing it directly? In contrast to the usual production methods, now there’s no need to take the limits of drilling or casting into account: The engineer can select the optimal course in her CAD system and let the laser do the rest.

This is one way that AM can make a significant contribution to achieving efficiency goals and emission targets. In addition, components can be made lighter without sacrificing stability. And due to these optimized designs, components benefit from less wear and tear and a longer service life. The lead-time of product development cycles is reduced by 75 percent, because AM can provide functional prototypes that can be implemented and validated in short timeframes. Using AM as a vehicle for fast technology validation leads to the abandonment of traditional and sequential development processes. Now, testing and validation of new concepts are fully integrated in the development process, and any necessary changes can be implemented much faster. This approach significantly reduces both development risks and development costs.

Reverse engineering is another application that benefits from AM. Siemens recently brought a 100-year-old Ruston Hornsby vintage car back to life using reverse engineering to recreate its steering box. With no original technical drawings available, Siemens digitally re-assembled the parts of the broken steering box and created an improved working model that could be additively manufactured. It took just five days to rebuild the steering box more accurately than using conventional manufacturing processes; and it’s more robust because it’s engineered as a single piece. Reverse engineering starts with understanding the task and creating working ideas, continues with selecting the right material and optimizing printing, and ends with the post processing.

AM holds enormous potential when rigorously applied in the production chain:

Rapid prototyping 75 percent reduction in development time

Because production with AM is much faster than conventional manufacturing, testing and development time for components is reduced accordingly. Early validation of new designs is another advantage.

Rapid manufacturing 85 percent faster manufacturing of entire burner set

AM technology industrialization creates new opportunities for spare part and supply chain enhancements, including the manufacturing of spare parts on demand and even close to the site.

Rapid repair 60 percent faster repairs to burners tips

Replacing conventional repair processes with AM not only significantly reduces repair time, it also offers the opportunity to modify repaired components to the latest design.

In the future, materials research will progress so that even highly stressed components in large gas turbines will be 3D printed, and additional additive manufacturing methods will open the door to printing larger pieces for huge steam turbines.

Copyright © 2019 by ASME
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