Design for additive manufacturing of cryogenic flexible pivot enabling on-demand customization, and reducing failure risks

Abstract Compliant mechanisms achieve motion through elastic deformation rather than contact surfaces, eliminating friction, wear, and lubrication requirements. Historically, conventional manufacturing processes have constrained both the design and adoption of these mechanisms in cryogenic and space applications. This work exploits the design freedom of Laser Powder Bed Fusion (LPBF) to propose a streamlined Design for Additive Manufacturing (DfAM) workflow for optimizing and customizing a flexure pivot operating at 4.2 K within the Mode Selector Mechanism (MSM). The methodology comprises three stages: (i) material selection and post-processing—316L stainless steel combined with stress annealing and HIP—to ensure cryogenic compatibility and fatigue strength; (ii) optimization of the Interlocked Lattice Flexure (ILF) geometry considering performance metrics (stroke, stiffness, guiding accuracy) and AM constraints (overhang, minimum feature size); and (iii) flexure thickness tuning to meet project-specific requirements while mitigating AM-induced variability, enabling rapid customization. Numerical and experimental validation confirmed compliance with design targets: $$\pm \, 3.5^\circ $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>±</mml:mo> <mml:mspace/> <mml:mn>3</mml:mn> <mml:mo>.</mml:mo> <mml:msup> <mml:mn>5</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:mrow> </mml:math> stroke, stiffness of 3.97 mN m/ $$^\circ $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mo>∘</mml:mo> </mml:mmultiscripts> </mml:math> , and fatigue life exceeding $$10^6$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>6</mml:mn> </mml:msup> </mml:math> cycles under over-testing conditions (115% of operational range). Failure analysis further demonstrated that the ILF design inherently localizes damage, preventing catastrophic failure and enhancing robustness for aerospace applications. These results underscore the transformative potential of AM for high-performance, customizable compliant mechanisms in extreme environments.