[ Additive Manufacturing ] of old and new impeller designs could be simultaneously made on the same build plate to compare results . The relatively small size of the impellers ( 60 millimeters in diameter ) necessitated the team ’ s development of a ‘ sacrificial shroud ’ – a temporary printed enclosure that held the blades true during manufacturing .
Sacrificial shrouds and smoother surfaces “ What was really interesting about this approach is that shrouded impellers are , for most current additive technology , basically untouchable because of all the traditional support structures they require ,” says Velo3D ’ s Karesh . “ We used a , not support-free , but reducedsupport approach . Mohawk was saying , ‘ we don ’ t need the shroud in the end , but the shroud makes our part better , so we ’ ll attach this thing that ’ s typically extremely hard to print – and just cut it off after .’ Using Velo3D ’ s technology , they were able to build that disposable shroud onto their impeller , get the airfoil and flow-path shapes they wanted , and then it was a very simple machining operation to remove the shroud .” Surface finish was another focus , as Mohawk engineer Rochelle Wooding explains : “ The surface was a bit rough in our early iterations . What was interesting about the sacrificial shroud was that it gave us a flow path through the blades that we could use to correct for roughness
“ Inconel was very attractive to us because it ’ s chemically inert enough and retains its mechanical properties ”
using extrusion honing ; it took some further iteration to determine how much material to add to the blades to achieve the required blade thickness that we wanted . The final surface finish we achieved is comparable to that of a cast part and suits our purposes aerodynamically .” What ’ s more , all critical design dimensions enabling proper impeller operation were within tolerances .
Future testing , forward outlook Next steps are retrofitting AORBs with the new impellers and testing them in field conditions . “ We expect that successful execution of these two tasks will fully demonstrate that 3D-printed Inconel parts delivered by LPBF technology are a viable and reliable alternative for manufacturing turbomachinery components ,” says Cordova . Work is already underway using AM for other blower parts like housings and volutes . Cordova is particularly proud of the professional credentials and work ethic of the two young women engineers who ’ ve been engaged in these recent in-house projects . “ I never really feel like I have an easy day here ,” Wooding says . “ But I really enjoy that !” She ’ s also keenly aware of the greater value of what they are doing : “ Through these DOE-funded projects we ’ ve been able to develop a library of common parts . Based on the original idea , we now have at least three completely different platforms that can serve different power capabilities to support progress for the clean energy of the future .”
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