[ Additive Manufacturing ]
funding [ through The Small Business Industrial Research Project ] supports our current partnership with Velo3D as well as our previous one with FuelCell Energy . An additional benefit is that this work is helping advance 3D printing technology in general as we learn more and more about its capabilities and potential .” Velo3D ’ s Mohawk-project leader Matt Karesh agrees . “ Working hand in hand with companies like Mohawk , who are willing to collaborate with us and give us feedback , drives progress on our internal process parameters and capabilities , and helps direct us as to how to make our print methodologies better ,” he says .
A nice price surprise The switch to AM was an eye-opener : “ Our traditional , subtractively manufactured impeller wheels were running up to $ 15,000 to $ 19,000 apiece ,” says Cordova . “ When we 3D printed them , in small batches of around eight units rather than one at a time , this dropped to $ 500 to $ 600 – a very significant cost reduction . “ As well as cutting manufacturing costs , LPBF is the one technology that could provide us with the design flexibility we were looking for . AM is indifferent to the number of impeller blades , their angles , or spacing – all of which have a direct impact on aerodynamic efficiency . We now have the geometric precision needed to achieve both higher-performance rotating turbomachinery designs and reduce associated manufacturing costs .”
Picking the perfect alloy For 3D printing impellers on a Velo3D Sapphire system ( at Duncan Machine , a contract manufacturer in Velo3D ’ s global network ), the choice was made to use Inconel 718 – one of the nickel-based alloys with a strong temperature tolerance that withstand the stress of rotation best . “ Inconel was very attractive to us because it ’ s chemically inert enough and retains its mechanical properties at pretty high temperatures that definitely surpass aluminum or
An SOFC power system with AORB highlighted . Photo courtesy of FCE .
Pictured from left to right : Mohawk ’ s Hannah Lea , Jose Luis Cordova and Rochelle Wooding
titanium ,” says Mohawk mechanical engineer Hannah Lea . Although Velo3D had already certified Inconel 718 for their machines , Mohawk did additional material studies to add to the body of knowledge about the 3D-printed version of the superalloy . “ Our tests demonstrated that LPBF 3D-printed Inconel 718 had mechanical properties , like yield stress and creep tolerance , that were higher than those of cast material ,” Lea says . “ This was more than adequate for high-stress centrifugal blower and compressor applications within the operational temperature range .”
Iteration made easy As their impeller work progressed , Mohawk ’ s engineers collaborated with Velo3D experts on design iterations , modifications and printing strategies . “ It was really interesting because we didn ’ t have to make any major design changes to the original impeller we were working with – with Velo3D ’ s Sapphire system we could just print what we wanted ,” says Cordova . “ We did do some process adjustments and tweaking in terms of support-structure considerations and surface-finish modifications .” Of course , tweaking is just another day in the office for design engineers . As the impeller project progressed , AM provided much faster turnaround times than casting or milling would have allowed , since parts could be printed , evaluated , iterated and printed again quickly . In subsequent 3D printing runs , multiple examples
32 Stainless Steel World March 2023 www . stainless-steel-world . net