Wärtsilä Corp., a lifecycle solutions leader for the marine and energy markets, required a robust impeller that would push the limits of design and functionality. After 500 hours of rigorous testing, the results are clear: a lighter, more efficient, additive manufacturing-built application that opens up new business potential for the engineering giant.
Pump impellers are widely used in the energy industry for fluid transportation, but varying use cases require a significant level of customization. As a result, impellers are produced in large numbers and kept in storage as backups. This avoids lead times of up to 20 weeks in case of failure, and guarantees uptime for a part crucial to a company’s capital.
With AM, applications can be printed on demand, reducing waste from having to overproduce to make things financially viable. Doing so also reduces lead times, and the need for storage can be minimized through digital inventories, on-premises manufacturing, and higher part-performing parts. AM also can provide innovative solutions in the spare parts business, such as cutting out prototyping by casting.
The project teamed Wärtsilä with SLM Solutions, nTopology, and Oqton to push the technology’s boundaries. It began with a functional redesign that would create weight reduction provided by nTopology software and the decision to realize the application on an SLM280 PS. This process used nTopology software to generate a complex lattice structure within the impeller and aligned it with the cylindrical axis, complementing the impeller design’s rotational nature. The field-driven design enabled the performance of structural analysis on the impeller to variably hollow and thicken the interior lattice beam thickness based on stress results.
The internal geometry and lattice design helped reduce weight while withstanding the required forces, and created stable AM process conditions. And the lattice’s thickness was easily scaled to meet carrying stresses. To maximize performance, the lattice is rotationally symmetric around the rotation axis to keep the part balanced while in use.
SLM Solutions’ Free Float software has been developed to overcome the barrier of printing surfaces with an angle less than 45°. Free Float enables the capability of printing surfaces with an angle of 20° for the application’s chosen material, IN718. Typically, surfaces with such angles require a supportive structure to be removed during post processing. With a complex pump impeller, eliminating the supports with tools can be difficult due to nooks. Therefore, less material consumption is needed, resulting in less post processing, both of which contribute to the productivity of the part.
Geometrical accuracy was increased through the predeformation of the simulated model with Oqton’s Amphyon tool, which enabled SLM Solutions to achieve a dimensionally accurate part to maximize its characteristics. The deformation of the component was calculated using a mechanical process simulation, considering the thermal stresses of the build process, stress relief, and support removal. Instead of meshing complex lattice structures, a new homogenization approach was used. The entire analysis was performed in just one hour and 35 minutes on a standard CAD workstation, yielding an impeller that was as light and resilient as the existing part, while the lead time were dramatically reduced.
In addition to the quick availability, the new part design will allow improvements to the system. This efficiency update can play a significant role in the energy sector by extending its technologies using AM. While avoiding the need for prototyping by casting—which includes the requirement of costly tooling parts—the fast design and printing process allowed SLM Solutions to overcome the traditional lifecycle and led to an early testing phase.
The requirements of the pump impeller were tested in a real-scale laboratory engine with multiple performance measurements. Real-world conditions, such as 120° C and a rotational speed over 2,600 rpm, were applied to validate the prototypes. The impeller was tested at different engine loads for more than 500 hours. No signs of wear and defects were detected, demonstrating the high performance of the material used.
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